I'm working on a 60s Delco car radio. Sorry the model number label is missing. But this circuit was used in zillions of Delco models for many years. I cannot get the 1.6 volts to the collector. I found the 2 volts but on the other side of the 8.2 ohm resistor the voltage is zero. I thought that maybe the resistor was open but it is not. I have 12 volts on both the emitter and base of the DS-501. I can attach a 1.5 volt battery and make it thump, but it makes no difference, there's no sound. The transistor is off and wont turn on. The fusible resistor gets warm, the bias control is not open. I cannot find any other open resistors or lands. I have replaced all the electrolytic capacitors. I have gone over it too many times and spent over 12 hours on it. I have never seen one like this before. This is extremely frustrating. Please help.
Thanks,
Dave
The amplifier section is on a separate PC board which includes the volume and tone controls. I have the 5 volt source and 2 volt source. But no matter what I do I get zero volts out at the speaker +, which is also the collector of the DS-501. I have replaced the transistor (DS-501) too. But I don't think that it's defective.
I meant to say 8.2K ohm, but left out the K for some reason. The 8.2K ohm resistor isn't open. But there's no 1.6 volts after the resistor or any resistor. But for some reason a 1.5 volt battery will make the speaker "thump".
Dave
:Hello All,
: I'm working on a 60s Delco car radio. Sorry the model number label is missing. But this circuit was used in zillions of Delco models for many years. I cannot get the 1.6 volts to the collector. I found the 2 volts but on the other side of the 8.2 ohm resistor the voltage is zero. I thought that maybe the resistor was open but it is not. I have 12 volts on both the emitter and base of the DS-501. I can attach a 1.5 volt battery and make it thump, but it makes no difference, there's no sound. The transistor is off and wont turn on. The fusible resistor gets warm, the bias control is not open. I cannot find any other open resistors or lands. I have replaced all the electrolytic capacitors. I have gone over it too many times and spent over 12 hours on it. I have never seen one like this before. This is extremely frustrating. Please help.
:
:Thanks,
:
:Dave
:
:The amplifier section is on a separate PC board which includes the volume and tone controls. I have the 5 volt source and 2 volt source. But no matter what I do I get zero volts out at the speaker +, which is also the collector of the DS-501. I have replaced the transistor (DS-501) too. But I don't think that it's defective.
There is no connection between the collector and the heat sink or the chassis. The battery wouldn't make the speaker thump if it was. I have to connect the + end of the battery to the collector, and the negative end to the chassis or heat sink. So that's not the problem.
Thanks,
Dave
: Dave- Make sure that the case of the DS-501 and/or it's heatsink is isolated from the radio chassis(ie:no continuity between them). There should be plastic/mica wafers or washers in place to provide insulation.
Have you tested the transistor or substituted another one?
Radiodoc
***************
:Walt,
: There is no connection between the collector and the heat sink or the chassis. The battery wouldn't make the speaker thump if it was. I have to connect the + end of the battery to the collector, and the negative end to the chassis or heat sink. So that's not the problem.
:
:Thanks,
:
:Dave
:: Dave- Make sure that the case of the DS-501 and/or it's heatsink is isolated from the radio chassis(ie:no continuity between them). There should be plastic/mica wafers or washers in place to provide insulation.
As I said in my second message:
"I have replaced the transistor (DS-501) too. But I don't think that it's defective."
Yes I did.
Thanks,
Dave
:Dave,
:
:Have you tested the transistor or substituted another one?
:
:Radiodoc
:***************
:
:
::Walt,
:: There is no connection between the collector and the heat sink or the chassis. The battery wouldn't make the speaker thump if it was. I have to connect the + end of the battery to the collector, and the negative end to the chassis or heat sink. So that's not the problem.
::
::Thanks,
::
::Dave
::: Dave- Make sure that the case of the DS-501 and/or it's heatsink is isolated from the radio chassis(ie:no continuity between them). There should be plastic/mica wafers or washers in place to provide insulation.
This is a PNP transistor. Look closely at base and emitter voltage. To be on the base needs to be negative in relation to emitter.
Norm
:Radiodoc,
: As I said in my second message:
:"I have replaced the transistor (DS-501) too. But I don't think that it's defective."
:
:Yes I did.
:
:Thanks,
:
:Dave
::Dave,
::
::Have you tested the transistor or substituted another one?
::
::Radiodoc
::***************
::
::
:::Walt,
::: There is no connection between the collector and the heat sink or the chassis. The battery wouldn't make the speaker thump if it was. I have to connect the + end of the battery to the collector, and the negative end to the chassis or heat sink. So that's not the problem.
:::
:::Thanks,
:::
:::Dave
:::: Dave- Make sure that the case of the DS-501 and/or it's heatsink is isolated from the radio chassis(ie:no continuity between them). There should be plastic/mica wafers or washers in place to provide insulation.
It isn't. Both voltages are the same. The base and emitter have the exact same voltage. What should I look at to get them correct? I knew it wasn't on. You are the first person to know that is the problem. But I need a little direction. What should I check first?
Thanks very much,
Dave
:Hi Dave
:
: This is a PNP transistor. Look closely at base and emitter voltage. To be on the base needs to be negative in relation to emitter.
:
:Norm
:
::Radiodoc,
:: As I said in my second message:
::"I have replaced the transistor (DS-501) too. But I don't think that it's defective."
::
::Yes I did.
::
::Thanks,
::
::Dave
:::Dave,
:::
:::Have you tested the transistor or substituted another one?
:::
:::Radiodoc
:::***************
:::
:::
::::Walt,
:::: There is no connection between the collector and the heat sink or the chassis. The battery wouldn't make the speaker thump if it was. I have to connect the + end of the battery to the collector, and the negative end to the chassis or heat sink. So that's not the problem.
::::
::::Thanks,
::::
::::Dave
::::: Dave- Make sure that the case of the DS-501 and/or it's heatsink is isolated from the radio chassis(ie:no continuity between them). There should be plastic/mica wafers or washers in place to provide insulation.
Usually, on these sets when the two voltages (base and emitter) are the same, the emitter resistor is open. But it's not open and gets quite hot to the touch. So this is an interesting problem.
Thanks,
Dave
:Norm,
: It isn't. Both voltages are the same. The base and emitter have the exact same voltage. What should I look at to get them correct? I knew it wasn't on. You are the first person to know that is the problem. But I need a little direction. What should I check first?
:
:Thanks very much,
:
:Dave
::Hi Dave
::
:: This is a PNP transistor. Look closely at base and emitter voltage. To be on the base needs to be negative in relation to emitter.
::
::Norm
::
:::Radiodoc,
::: As I said in my second message:
:::"I have replaced the transistor (DS-501) too. But I don't think that it's defective."
:::
:::Yes I did.
:::
:::Thanks,
:::
:::Dave
::::Dave,
::::
::::Have you tested the transistor or substituted another one?
::::
::::Radiodoc
::::***************
::::
::::
:::::Walt,
::::: There is no connection between the collector and the heat sink or the chassis. The battery wouldn't make the speaker thump if it was. I have to connect the + end of the battery to the collector, and the negative end to the chassis or heat sink. So that's not the problem.
:::::
:::::Thanks,
:::::
:::::Dave
:::::: Dave- Make sure that the case of the DS-501 and/or it's heatsink is isolated from the radio chassis(ie:no continuity between them). There should be plastic/mica wafers or washers in place to provide insulation.
Usually, on these sets when the two voltages (base and emitter) are the same, the emitter resistor is open. But it's not open and gets quite hot to the touch. So this is an interesting problem.
Thanks,
Dave
:Norm,
: It isn't. Both voltages are the same. The base and emitter have the exact same voltage. What should I look at to get them correct? I knew it wasn't on. You are the first person to know that is the problem. But I need a little direction. What should I check first?
:
:Thanks very much,
:
:Dave
::Hi Dave
::
:: This is a PNP transistor. Look closely at base and emitter voltage. To be on the base needs to be negative in relation to emitter.
::
::Norm
::
:::Radiodoc,
::: As I said in my second message:
:::"I have replaced the transistor (DS-501) too. But I don't think that it's defective."
:::
:::Yes I did.
:::
:::Thanks,
:::
:::Dave
::::Dave,
::::
::::Have you tested the transistor or substituted another one?
::::
::::Radiodoc
::::***************
::::
::::
:::::Walt,
::::: There is no connection between the collector and the heat sink or the chassis. The battery wouldn't make the speaker thump if it was. I have to connect the + end of the battery to the collector, and the negative end to the chassis or heat sink. So that's not the problem.
:::::
:::::Thanks,
:::::
:::::Dave
:::::: Dave- Make sure that the case of the DS-501 and/or it's heatsink is isolated from the radio chassis(ie:no continuity between them). There should be plastic/mica wafers or washers in place to provide insulation.
Yes, this looks similar but I think that the set I'm working on is from 1968 or 1969. I'll try disconnecting the transistor and checking things later this evening.
Thanks,
Dave
::You don't mention the amount of current being drawn by the radio under these conditions, but I'm guessing there is a base to emitter short, not necessarily the transistor itself. I used this schematic: http://techpreservation.dyndns.org/schematics/63/63_Delco_AC-3216_23.djvu which is similar to the radio in my 66 Corvair. There should be a 0.2 volt drop across the E/B junction from 10.8 to 10.6 volts and 1.6 volts on the collector. Total system current should be about 1.2 amps. Try removing the transistor and check the current again. Oops, I mean the current draw with and without the transistor to see if it makes a difference.
If its like the 66 'Vette I did, you should be testing only with the req'd speaker attached. In my case it was a speaker/inductor combo, with the inductor paralled with the VC. On mine, the heatsink/collector were connected, but isolated from chassis. The plus (+) speaker wire connected to the heatsink. Have you tried adjusting the bias pot, while measuring the collector voltage. DC coupling from 1st audio amp to output will affect DC bias at the DS501 base. My good DS501 measured bad on a B&K beta checker. Supposedly it has an additional base/emitter internal diode, which affects the testing.
marv
:Anthony,
: Yes, this looks similar but I think that the set I'm working on is from 1968 or 1969. I'll try disconnecting the transistor and checking things later this evening.
:
:Thanks,
:
:Dave
:::You don't mention the amount of current being drawn by the radio under these conditions, but I'm guessing there is a base to emitter short, not necessarily the transistor itself. I used this schematic: http://techpreservation.dyndns.org/schematics/63/63_Delco_AC-3216_23.djvu which is similar to the radio in my 66 Corvair. There should be a 0.2 volt drop across the E/B junction from 10.8 to 10.6 volts and 1.6 volts on the collector. Total system current should be about 1.2 amps. Try removing the transistor and check the current again. Oops, I mean the current draw with and without the transistor to see if it makes a difference.
I was just holding back and waiting for the other shoe to drop, as far as the circuitry design was concerned, as I was not ruling out the front end even utilizing low plate potential tubes in the front end and eventually feeding the AF driver transformer. But, with the forthcoming info, seems like an all xstr unit is the agreed upon design.
If you willl consult with the schematic suggested, it just doesn’t agree with your being able to read a DYNAMIC 12 volt presence
on the collector of the DS-501 such as you profess to be reading.
You did not confirm if you have all of the unit…especially the factory speaker and its autotransformer design of low impedance A.F.output transformer.
Looking at the 12 VDC power supply buss….. it comes upwards from the bottom and passes thru a .47 ohm emitter/fusible resistor and feeds the DS 501 emitter. Simultaneously there is 12VDC routed off to the left to the 10 ohm and 175 ohm voltage divider pair that establish the operational quiescent bias on the base of the ‘501.
Item 36….1K… electrolytic provides low freq AC shunt bypassing for the stage.
Lowering the resistance setting of item 74 …bias pot…increases the base bias…collector consumption..
Soooooo …..with you having such an exorbitantly high collector voltage present, and considering stock speaker and output transformer connected up, it just seems that you must have an open somewhere from the blue buss from the collector to its eventual passage thru the output transformer and its final ground connection..
(Now there is no chance that there is merely / solely a test speaker connected from DS-501 collector to ground,….is there ? as that could account for the possible higher voltage being able to be developed across the collector to ground loop. Otherwise, that collector is seeing a very low Z into that autotransformer circuitry.)
Consulting the schema , seems like no problem with speaker shunt switch (73) if you can get a thump from the unit.
Assuredly with such a heat cooked unit thru the decades of July's and August's bakings , all of the red boxed electrolytics are due a Prev Maint replacement.
Lastly, to make a dynamic operational test of the current gain of your output xstr, merely power up and take a 100 ohm resistor and a test lead and ground one clip end of the test lead and clip the other end onto one lead of the resistor and use the free end of the resistor to scratch….like a match…the base terminal of the DS-501, with a good unit a healthy “scratch” should come forth from the speaker. To test the DS-26 driver circuit, use the same procedure to its base, but use a 1K value of resistor instead.
Standing by…..
SCHEMATICUS REFERENCIMUS:
73's de Edd
Pot shown in the base circuit (74) is usually a cheap screw driver adjustment. They can be open causing base and emitter to be the same voltage.
Norm
:
:
:
:
:
:
:I was just holding back and waiting for the other shoe to drop, as far as the circuitry design was concerned, as I was not ruling out the front end even utilizing low plate potential tubes in the front end and eventually feeding the AF driver transformer. But, with the forthcoming info, seems like an all xstr unit is the agreed upon design.
:
:
:If you willl consult with the schematic suggested, it just doesn’t agree with your being able to read a DYNAMIC 12 volt presence
:on the collector of the DS-501 such as you profess to be reading.
:
:You did not confirm if you have all of the unit…especially the factory speaker and its autotransformer design of low impedance A.F.output transformer.
:
:
:
:Looking at the 12 VDC power supply buss….. it comes upwards from the bottom and passes thru a .47 ohm emitter/fusible resistor and feeds the DS 501 emitter. Simultaneously there is 12VDC routed off to the left to the 10 ohm and 175 ohm voltage divider pair that establish the operational quiescent bias on the base of the ‘501.
:
:Item 36….1K… electrolytic provides low freq AC shunt bypassing for the stage.
:
:Lowering the resistance setting of item 74 …bias pot…increases the base bias…collector consumption..
:
:Soooooo …..with you having such an exorbitantly high collector voltage present, and considering stock speaker and output transformer connected up, it just seems that you must have an open somewhere from the blue buss from the collector to its eventual passage thru the output transformer and its final ground connection..
:
:
:
:(Now there is no chance that there is merely / solely a test speaker connected from DS-501 collector to ground,….is there ? as that could account for the possible higher voltage being able to be developed across the collector to ground loop. Otherwise, that collector is seeing a very low Z into that autotransformer circuitry.)
:
:
:
:Consulting the schema , seems like no problem with speaker shunt switch (73) if you can get a thump from the unit.
:
:
:
:Assuredly with such a heat cooked unit thru the decades of July's and August's bakings , all of the red boxed electrolytics are due a Prev Maint replacement.
:
:
:
:Lastly, to make a dynamic operational test of the current gain of your output xstr, merely power up and take a 100 ohm resistor and a test lead and ground one clip end of the test lead and clip the other end onto one lead of the resistor and use the free end of the resistor to scratch….like a match…the base terminal of the DS-501, with a good unit a healthy “scratch” should come forth from the speaker. To test the DS-26 driver circuit, use the same procedure to its base, but use a 1K value of resistor instead.
:
:
:
:Standing by…..
:
:
:
:SCHEMATICUS REFERENCIMUS:
:
:
:
:
:
:
:
:
:73's de Edd
:
:
The control (74) is not open. It's working.
Thanks,
Dave
:Hi Dave
:
: Pot shown in the base circuit (74) is usually a cheap screw driver adjustment. They can be open causing base and emitter to be the same voltage.
:
:Norm
:
::
::
::
::
::
::
::I was just holding back and waiting for the other shoe to drop, as far as the circuitry design was concerned, as I was not ruling out the front end even utilizing low plate potential tubes in the front end and eventually feeding the AF driver transformer. But, with the forthcoming info, seems like an all xstr unit is the agreed upon design.
::
::
::If you willl consult with the schematic suggested, it just doesn’t agree with your being able to read a DYNAMIC 12 volt presence
::on the collector of the DS-501 such as you profess to be reading.
::
::You did not confirm if you have all of the unit…especially the factory speaker and its autotransformer design of low impedance A.F.output transformer.
::
::
::
::Looking at the 12 VDC power supply buss….. it comes upwards from the bottom and passes thru a .47 ohm emitter/fusible resistor and feeds the DS 501 emitter. Simultaneously there is 12VDC routed off to the left to the 10 ohm and 175 ohm voltage divider pair that establish the operational quiescent bias on the base of the ‘501.
::
::Item 36….1K… electrolytic provides low freq AC shunt bypassing for the stage.
::
::Lowering the resistance setting of item 74 …bias pot…increases the base bias…collector consumption..
::
::Soooooo …..with you having such an exorbitantly high collector voltage present, and considering stock speaker and output transformer connected up, it just seems that you must have an open somewhere from the blue buss from the collector to its eventual passage thru the output transformer and its final ground connection..
::
::
::
::(Now there is no chance that there is merely / solely a test speaker connected from DS-501 collector to ground,….is there ? as that could account for the possible higher voltage being able to be developed across the collector to ground loop. Otherwise, that collector is seeing a very low Z into that autotransformer circuitry.)
::
::
::
::Consulting the schema , seems like no problem with speaker shunt switch (73) if you can get a thump from the unit.
::
::
::
::Assuredly with such a heat cooked unit thru the decades of July's and August's bakings , all of the red boxed electrolytics are due a Prev Maint replacement.
::
::
::
::Lastly, to make a dynamic operational test of the current gain of your output xstr, merely power up and take a 100 ohm resistor and a test lead and ground one clip end of the test lead and clip the other end onto one lead of the resistor and use the free end of the resistor to scratch….like a match…the base terminal of the DS-501, with a good unit a healthy “scratch” should come forth from the speaker. To test the DS-26 driver circuit, use the same procedure to its base, but use a 1K value of resistor instead.
::
::
::
::Standing by…..
::
::
::
::SCHEMATICUS REFERENCIMUS:
::
::
::
::
::
::
::
::
::73's de Edd
::
::
This set has the three terminals in back labeled, + 12v, Speaker, and negative. It doesn't have the shorting switch. The transformer is located on this radio, not on the speaker. I have the book, "Practical Transistor servicing" By Bill Caldwell. This is the 1960 edition, the first edition. So I was pretty sure I knew this circuit. But occasionally I get a stumper like this. I have another set that's almost exactly the same and it works fine. Just a second, I'll get the model number of that. 7303231 is the model number of the working radio. It has the same small board with the volume control and audio section. I think that the schematic from that one would probably help with this one. I'll check everything some more this evening.
Thanks,
Dave
:
:
:
:
:
:
:I was just holding back and waiting for the other shoe to drop, as far as the circuitry design was concerned, as I was not ruling out the front end even utilizing low plate potential tubes in the front end and eventually feeding the AF driver transformer. But, with the forthcoming info, seems like an all xstr unit is the agreed upon design.
:
:
:If you willl consult with the schematic suggested, it just doesn’t agree with your being able to read a DYNAMIC 12 volt presence
:on the collector of the DS-501 such as you profess to be reading.
:
:You did not confirm if you have all of the unit…especially the factory speaker and its autotransformer design of low impedance A.F.output transformer.
:
:
:
:Looking at the 12 VDC power supply buss….. it comes upwards from the bottom and passes thru a .47 ohm emitter/fusible resistor and feeds the DS 501 emitter. Simultaneously there is 12VDC routed off to the left to the 10 ohm and 175 ohm voltage divider pair that establish the operational quiescent bias on the base of the ‘501.
:
:Item 36….1K… electrolytic provides low freq AC shunt bypassing for the stage.
:
:Lowering the resistance setting of item 74 …bias pot…increases the base bias…collector consumption..
:
:Soooooo …..with you having such an exorbitantly high collector voltage present, and considering stock speaker and output transformer connected up, it just seems that you must have an open somewhere from the blue buss from the collector to its eventual passage thru the output transformer and its final ground connection..
:
:
:
:(Now there is no chance that there is merely / solely a test speaker connected from DS-501 collector to ground,….is there ? as that could account for the possible higher voltage being able to be developed across the collector to ground loop. Otherwise, that collector is seeing a very low Z into that autotransformer circuitry.)
:
:
:
:Consulting the schema , seems like no problem with speaker shunt switch (73) if you can get a thump from the unit.
:
:
:
:Assuredly with such a heat cooked unit thru the decades of July's and August's bakings , all of the red boxed electrolytics are due a Prev Maint replacement.
:
:
:
:Lastly, to make a dynamic operational test of the current gain of your output xstr, merely power up and take a 100 ohm resistor and a test lead and ground one clip end of the test lead and clip the other end onto one lead of the resistor and use the free end of the resistor to scratch….like a match…the base terminal of the DS-501, with a good unit a healthy “scratch” should come forth from the speaker. To test the DS-26 driver circuit, use the same procedure to its base, but use a 1K value of resistor instead.
:
:
:
:Standing by…..
:
:
:
:SCHEMATICUS REFERENCIMUS:
:
:
:
:
:
:
:
:
:73's de Edd
:
:
I just turned it on again today and it worked for about 12 seconds and then stopped. I turned off and on again, and it worked and stopped but will not turn on again. I tried another fuse resistor and it wont come on. The voltages I have on the base and emitter, not necessarily in this order 14.81 volts and 14.83 volts. My battery has a charger attached to it. I heard FM and it sounds great, if it would just stay on. My speaker connections are perfect. I can make the speaker "thump" using a 1.5 volt battery. This was the method used in the book to see if the speaker connections are good. There must be some intermittent connection on that small board. I will probably have to take it out and study it very closely. Maybe I have an intermittent resistor? Maybe a land on the board is intermittent. I have measured just about everything and the connections are perfect, as far as I can tell.
This set is frustrating but somewhat more interesting that ones I usually see.
Thanks,
Dave
:Edd,
: This set has the three terminals in back labeled, + 12v, Speaker, and negative. It doesn't have the shorting switch. The transformer is located on this radio, not on the speaker. I have the book, "Practical Transistor servicing" By Bill Caldwell. This is the 1960 edition, the first edition. So I was pretty sure I knew this circuit. But occasionally I get a stumper like this. I have another set that's almost exactly the same and it works fine. Just a second, I'll get the model number of that. 7303231 is the model number of the working radio. It has the same small board with the volume control and audio section. I think that the schematic from that one would probably help with this one. I'll check everything some more this evening.
:
:Thanks,
:
:Dave
::
::
::
::
::
::
::I was just holding back and waiting for the other shoe to drop, as far as the circuitry design was concerned, as I was not ruling out the front end even utilizing low plate potential tubes in the front end and eventually feeding the AF driver transformer. But, with the forthcoming info, seems like an all xstr unit is the agreed upon design.
::
::
::If you willl consult with the schematic suggested, it just doesn’t agree with your being able to read a DYNAMIC 12 volt presence
::on the collector of the DS-501 such as you profess to be reading.
::
::You did not confirm if you have all of the unit…especially the factory speaker and its autotransformer design of low impedance A.F.output transformer.
::
::
::
::Looking at the 12 VDC power supply buss….. it comes upwards from the bottom and passes thru a .47 ohm emitter/fusible resistor and feeds the DS 501 emitter. Simultaneously there is 12VDC routed off to the left to the 10 ohm and 175 ohm voltage divider pair that establish the operational quiescent bias on the base of the ‘501.
::
::Item 36….1K… electrolytic provides low freq AC shunt bypassing for the stage.
::
::Lowering the resistance setting of item 74 …bias pot…increases the base bias…collector consumption..
::
::Soooooo …..with you having such an exorbitantly high collector voltage present, and considering stock speaker and output transformer connected up, it just seems that you must have an open somewhere from the blue buss from the collector to its eventual passage thru the output transformer and its final ground connection..
::
::
::
::(Now there is no chance that there is merely / solely a test speaker connected from DS-501 collector to ground,….is there ? as that could account for the possible higher voltage being able to be developed across the collector to ground loop. Otherwise, that collector is seeing a very low Z into that autotransformer circuitry.)
::
::
::
::Consulting the schema , seems like no problem with speaker shunt switch (73) if you can get a thump from the unit.
::
::
::
::Assuredly with such a heat cooked unit thru the decades of July's and August's bakings , all of the red boxed electrolytics are due a Prev Maint replacement.
::
::
::
::Lastly, to make a dynamic operational test of the current gain of your output xstr, merely power up and take a 100 ohm resistor and a test lead and ground one clip end of the test lead and clip the other end onto one lead of the resistor and use the free end of the resistor to scratch….like a match…the base terminal of the DS-501, with a good unit a healthy “scratch” should come forth from the speaker. To test the DS-26 driver circuit, use the same procedure to its base, but use a 1K value of resistor instead.
::
::
::
::Standing by…..
::
::
::
::SCHEMATICUS REFERENCIMUS:
::
::
::
::
::
::
::
::
::73's de Edd
::
::
It would sure help if we knew exactly what model radio you're working on!!
Your other working radio, model 7303231 is a 1968 Chevrolet AM/FM/Stereo radio. IF the problem radio is also an AM/FM/Stereo radio--- are you aware that it requires either the multiplex unit or a "jumper" plug to be installed for the radio to work? If there is a 9-pin socket on the back or side of the radio, it requires those.
For reference, the 1968 Chevy AM/FM non-stereo (Corvette) is 7302721. Other 66, 67, 68, Delco AM/FM radios of that era that use the separate audio board are similar.
On this audio board, the two DS-66 driver transistors and the DS-501 are "direct coupled". Any problems with the driver circuits will upset the output. The 10mfd electrolytic coupling the audio from the volume control to the base of the first DS-66 is prone to going open.
Maybe Edd will favor us with one of his great schematics to see if this is indeed the radio you have?
No voltage on the collector and a .47 fuse resistor getting hot sounds to me like a shorted or very leaky DS-501 (I know you tried another one!), or a short or serious leak on the collector line. Double check the 1.5 ohm speaker choke and the output electrolytic, either a 4mfd or 15mfd for different 1968 Delco radios. Some of these radios also had a "spark plate" on the speaker line.
Also check along the feedback loop that is connected to the collector (1.8k and 8.2k resistors), leading back to the input of the audio amp circuit.
Meade
:Edd,
: I just turned it on again today and it worked for about 12 seconds and then stopped. I turned off and on again, and it worked and stopped but will not turn on again. I tried another fuse resistor and it wont come on. The voltages I have on the base and emitter, not necessarily in this order 14.81 volts and 14.83 volts. My battery has a charger attached to it. I heard FM and it sounds great, if it would just stay on. My speaker connections are perfect. I can make the speaker "thump" using a 1.5 volt battery. This was the method used in the book to see if the speaker connections are good. There must be some intermittent connection on that small board. I will probably have to take it out and study it very closely. Maybe I have an intermittent resistor? Maybe a land on the board is intermittent. I have measured just about everything and the connections are perfect, as far as I can tell.
: This set is frustrating but somewhat more interesting that ones I usually see.
:
:Thanks,
:
:Dave
:
:
::Edd,
:: This set has the three terminals in back labeled, + 12v, Speaker, and negative. It doesn't have the shorting switch. The transformer is located on this radio, not on the speaker. I have the book, "Practical Transistor servicing" By Bill Caldwell. This is the 1960 edition, the first edition. So I was pretty sure I knew this circuit. But occasionally I get a stumper like this. I have another set that's almost exactly the same and it works fine. Just a second, I'll get the model number of that. 7303231 is the model number of the working radio. It has the same small board with the volume control and audio section. I think that the schematic from that one would probably help with this one. I'll check everything some more this evening.
::
::Thanks,
::
::Dave
:::
:::
:::
:::
:::
:::
:::I was just holding back and waiting for the other shoe to drop, as far as the circuitry design was concerned, as I was not ruling out the front end even utilizing low plate potential tubes in the front end and eventually feeding the AF driver transformer. But, with the forthcoming info, seems like an all xstr unit is the agreed upon design.
:::
:::
:::If you willl consult with the schematic suggested, it just doesn’t agree with your being able to read a DYNAMIC 12 volt presence
:::on the collector of the DS-501 such as you profess to be reading.
:::
:::You did not confirm if you have all of the unit…especially the factory speaker and its autotransformer design of low impedance A.F.output transformer.
:::
:::
:::
:::Looking at the 12 VDC power supply buss….. it comes upwards from the bottom and passes thru a .47 ohm emitter/fusible resistor and feeds the DS 501 emitter. Simultaneously there is 12VDC routed off to the left to the 10 ohm and 175 ohm voltage divider pair that establish the operational quiescent bias on the base of the ‘501.
:::
:::Item 36….1K… electrolytic provides low freq AC shunt bypassing for the stage.
:::
:::Lowering the resistance setting of item 74 …bias pot…increases the base bias…collector consumption..
:::
:::Soooooo …..with you having such an exorbitantly high collector voltage present, and considering stock speaker and output transformer connected up, it just seems that you must have an open somewhere from the blue buss from the collector to its eventual passage thru the output transformer and its final ground connection..
:::
:::
:::
:::(Now there is no chance that there is merely / solely a test speaker connected from DS-501 collector to ground,….is there ? as that could account for the possible higher voltage being able to be developed across the collector to ground loop. Otherwise, that collector is seeing a very low Z into that autotransformer circuitry.)
:::
:::
:::
:::Consulting the schema , seems like no problem with speaker shunt switch (73) if you can get a thump from the unit.
:::
:::
:::
:::Assuredly with such a heat cooked unit thru the decades of July's and August's bakings , all of the red boxed electrolytics are due a Prev Maint replacement.
:::
:::
:::
:::Lastly, to make a dynamic operational test of the current gain of your output xstr, merely power up and take a 100 ohm resistor and a test lead and ground one clip end of the test lead and clip the other end onto one lead of the resistor and use the free end of the resistor to scratch….like a match…the base terminal of the DS-501, with a good unit a healthy “scratch” should come forth from the speaker. To test the DS-26 driver circuit, use the same procedure to its base, but use a 1K value of resistor instead.
:::
:::
:::
:::Standing by…..
:::
:::
:::
:::SCHEMATICUS REFERENCIMUS:
:::
:::
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::
The 7303231 is an AM/FM, but it's not a stereo. It has a single DS-501 and a Single speaker connection. It's mono, unless, as you mentioned, a multiplex adaptor is used. Yes, the set that's not working or working very intermittently, is also an AM/FM Mono radio. It has a signal seeker too.
The two radios are almost identical. But the one that's not working doesn't have the multiplex jack. What remains of the model number looks like 730 but the rest is torn off.
I turned it on a little while ago and got the thump and it did work briefly but it refuses to work again. I don't know why it worked. That was the first time I had heard any sound at all from it.
Thanks,
Dave
:Dave,
:It would sure help if we knew exactly what model radio you're working on!!
:
:Your other working radio, model 7303231 is a 1968 Chevrolet AM/FM/Stereo radio. IF the problem radio is also an AM/FM/Stereo radio--- are you aware that it requires either the multiplex unit or a "jumper" plug to be installed for the radio to work? If there is a 9-pin socket on the back or side of the radio, it requires those.
:
:For reference, the 1968 Chevy AM/FM non-stereo (Corvette) is 7302721. Other 66, 67, 68, Delco AM/FM radios of that era that use the separate audio board are similar.
:On this audio board, the two DS-66 driver transistors and the DS-501 are "direct coupled". Any problems with the driver circuits will upset the output. The 10mfd electrolytic coupling the audio from the volume control to the base of the first DS-66 is prone to going open.
:
:Maybe Edd will favor us with one of his great schematics to see if this is indeed the radio you have?
:
:No voltage on the collector and a .47 fuse resistor getting hot sounds to me like a shorted or very leaky DS-501 (I know you tried another one!), or a short or serious leak on the collector line. Double check the 1.5 ohm speaker choke and the output electrolytic, either a 4mfd or 15mfd for different 1968 Delco radios. Some of these radios also had a "spark plate" on the speaker line.
:Also check along the feedback loop that is connected to the collector (1.8k and 8.2k resistors), leading back to the input of the audio amp circuit.
:
:Meade
:
:
:
::Edd,
:: I just turned it on again today and it worked for about 12 seconds and then stopped. I turned off and on again, and it worked and stopped but will not turn on again. I tried another fuse resistor and it wont come on. The voltages I have on the base and emitter, not necessarily in this order 14.81 volts and 14.83 volts. My battery has a charger attached to it. I heard FM and it sounds great, if it would just stay on. My speaker connections are perfect. I can make the speaker "thump" using a 1.5 volt battery. This was the method used in the book to see if the speaker connections are good. There must be some intermittent connection on that small board. I will probably have to take it out and study it very closely. Maybe I have an intermittent resistor? Maybe a land on the board is intermittent. I have measured just about everything and the connections are perfect, as far as I can tell.
:: This set is frustrating but somewhat more interesting that ones I usually see.
::
::Thanks,
::
::Dave
::
::
:::Edd,
::: This set has the three terminals in back labeled, + 12v, Speaker, and negative. It doesn't have the shorting switch. The transformer is located on this radio, not on the speaker. I have the book, "Practical Transistor servicing" By Bill Caldwell. This is the 1960 edition, the first edition. So I was pretty sure I knew this circuit. But occasionally I get a stumper like this. I have another set that's almost exactly the same and it works fine. Just a second, I'll get the model number of that. 7303231 is the model number of the working radio. It has the same small board with the volume control and audio section. I think that the schematic from that one would probably help with this one. I'll check everything some more this evening.
:::
:::Thanks,
:::
:::Dave
::::
::::
::::
::::
::::
::::
::::I was just holding back and waiting for the other shoe to drop, as far as the circuitry design was concerned, as I was not ruling out the front end even utilizing low plate potential tubes in the front end and eventually feeding the AF driver transformer. But, with the forthcoming info, seems like an all xstr unit is the agreed upon design.
::::
::::
::::If you willl consult with the schematic suggested, it just doesn’t agree with your being able to read a DYNAMIC 12 volt presence
::::on the collector of the DS-501 such as you profess to be reading.
::::
::::You did not confirm if you have all of the unit…especially the factory speaker and its autotransformer design of low impedance A.F.output transformer.
::::
::::
::::
::::Looking at the 12 VDC power supply buss….. it comes upwards from the bottom and passes thru a .47 ohm emitter/fusible resistor and feeds the DS 501 emitter. Simultaneously there is 12VDC routed off to the left to the 10 ohm and 175 ohm voltage divider pair that establish the operational quiescent bias on the base of the ‘501.
::::
::::Item 36….1K… electrolytic provides low freq AC shunt bypassing for the stage.
::::
::::Lowering the resistance setting of item 74 …bias pot…increases the base bias…collector consumption..
::::
::::Soooooo …..with you having such an exorbitantly high collector voltage present, and considering stock speaker and output transformer connected up, it just seems that you must have an open somewhere from the blue buss from the collector to its eventual passage thru the output transformer and its final ground connection..
::::
::::
::::
::::(Now there is no chance that there is merely / solely a test speaker connected from DS-501 collector to ground,….is there ? as that could account for the possible higher voltage being able to be developed across the collector to ground loop. Otherwise, that collector is seeing a very low Z into that autotransformer circuitry.)
::::
::::
::::
::::Consulting the schema , seems like no problem with speaker shunt switch (73) if you can get a thump from the unit.
::::
::::
::::
::::Assuredly with such a heat cooked unit thru the decades of July's and August's bakings , all of the red boxed electrolytics are due a Prev Maint replacement.
::::
::::
::::
::::Lastly, to make a dynamic operational test of the current gain of your output xstr, merely power up and take a 100 ohm resistor and a test lead and ground one clip end of the test lead and clip the other end onto one lead of the resistor and use the free end of the resistor to scratch….like a match…the base terminal of the DS-501, with a good unit a healthy “scratch” should come forth from the speaker. To test the DS-26 driver circuit, use the same procedure to its base, but use a 1K value of resistor instead.
::::
::::
::::
::::Standing by…..
::::
::::
::::
::::SCHEMATICUS REFERENCIMUS:
::::
::::
::::
::::
::::
::::
::::
::::
::::73's de Edd
::::
::::
The only Delco AM/FM/ WB radios I can find with a model number starting with "730" are the 1967 Olds model 7300103, and the 1968 Olds 7303173 and Toronado 7303243.
All three use the same audio circuit, like the one I mentioned in my earlier post. Something else to check; since it is a signal seeker, there is also a "Mute" function added to silence the radio during "search". This operates through a contact/s on the search relay and the solenoid tied to the audio input stages.
Meade
:MAG,
: The 7303231 is an AM/FM, but it's not a stereo. It has a single DS-501 and a Single speaker connection. It's mono, unless, as you mentioned, a multiplex adaptor is used. Yes, the set that's not working or working very intermittently, is also an AM/FM Mono radio. It has a signal seeker too.
: The two radios are almost identical. But the one that's not working doesn't have the multiplex jack. What remains of the model number looks like 730 but the rest is torn off.
: I turned it on a little while ago and got the thump and it did work briefly but it refuses to work again. I don't know why it worked. That was the first time I had heard any sound at all from it.
:
:Thanks,
:
:Dave
::Dave,
::It would sure help if we knew exactly what model radio you're working on!!
::
::Your other working radio, model 7303231 is a 1968 Chevrolet AM/FM/Stereo radio. IF the problem radio is also an AM/FM/Stereo radio--- are you aware that it requires either the multiplex unit or a "jumper" plug to be installed for the radio to work? If there is a 9-pin socket on the back or side of the radio, it requires those.
::
::For reference, the 1968 Chevy AM/FM non-stereo (Corvette) is 7302721. Other 66, 67, 68, Delco AM/FM radios of that era that use the separate audio board are similar.
::On this audio board, the two DS-66 driver transistors and the DS-501 are "direct coupled". Any problems with the driver circuits will upset the output. The 10mfd electrolytic coupling the audio from the volume control to the base of the first DS-66 is prone to going open.
::
::Maybe Edd will favor us with one of his great schematics to see if this is indeed the radio you have?
::
::No voltage on the collector and a .47 fuse resistor getting hot sounds to me like a shorted or very leaky DS-501 (I know you tried another one!), or a short or serious leak on the collector line. Double check the 1.5 ohm speaker choke and the output electrolytic, either a 4mfd or 15mfd for different 1968 Delco radios. Some of these radios also had a "spark plate" on the speaker line.
::Also check along the feedback loop that is connected to the collector (1.8k and 8.2k resistors), leading back to the input of the audio amp circuit.
::
::Meade
::
::
::
:::Edd,
::: I just turned it on again today and it worked for about 12 seconds and then stopped. I turned off and on again, and it worked and stopped but will not turn on again. I tried another fuse resistor and it wont come on. The voltages I have on the base and emitter, not necessarily in this order 14.81 volts and 14.83 volts. My battery has a charger attached to it. I heard FM and it sounds great, if it would just stay on. My speaker connections are perfect. I can make the speaker "thump" using a 1.5 volt battery. This was the method used in the book to see if the speaker connections are good. There must be some intermittent connection on that small board. I will probably have to take it out and study it very closely. Maybe I have an intermittent resistor? Maybe a land on the board is intermittent. I have measured just about everything and the connections are perfect, as far as I can tell.
::: This set is frustrating but somewhat more interesting that ones I usually see.
:::
:::Thanks,
:::
:::Dave
:::
:::
::::Edd,
:::: This set has the three terminals in back labeled, + 12v, Speaker, and negative. It doesn't have the shorting switch. The transformer is located on this radio, not on the speaker. I have the book, "Practical Transistor servicing" By Bill Caldwell. This is the 1960 edition, the first edition. So I was pretty sure I knew this circuit. But occasionally I get a stumper like this. I have another set that's almost exactly the same and it works fine. Just a second, I'll get the model number of that. 7303231 is the model number of the working radio. It has the same small board with the volume control and audio section. I think that the schematic from that one would probably help with this one. I'll check everything some more this evening.
::::
::::Thanks,
::::
::::Dave
:::::
:::::
:::::
:::::
:::::
:::::
:::::I was just holding back and waiting for the other shoe to drop, as far as the circuitry design was concerned, as I was not ruling out the front end even utilizing low plate potential tubes in the front end and eventually feeding the AF driver transformer. But, with the forthcoming info, seems like an all xstr unit is the agreed upon design.
:::::
:::::
:::::If you willl consult with the schematic suggested, it just doesn’t agree with your being able to read a DYNAMIC 12 volt presence
:::::on the collector of the DS-501 such as you profess to be reading.
:::::
:::::You did not confirm if you have all of the unit…especially the factory speaker and its autotransformer design of low impedance A.F.output transformer.
:::::
:::::
:::::
:::::Looking at the 12 VDC power supply buss….. it comes upwards from the bottom and passes thru a .47 ohm emitter/fusible resistor and feeds the DS 501 emitter. Simultaneously there is 12VDC routed off to the left to the 10 ohm and 175 ohm voltage divider pair that establish the operational quiescent bias on the base of the ‘501.
:::::
:::::Item 36….1K… electrolytic provides low freq AC shunt bypassing for the stage.
:::::
:::::Lowering the resistance setting of item 74 …bias pot…increases the base bias…collector consumption..
:::::
:::::Soooooo …..with you having such an exorbitantly high collector voltage present, and considering stock speaker and output transformer connected up, it just seems that you must have an open somewhere from the blue buss from the collector to its eventual passage thru the output transformer and its final ground connection..
:::::
:::::
:::::
:::::(Now there is no chance that there is merely / solely a test speaker connected from DS-501 collector to ground,….is there ? as that could account for the possible higher voltage being able to be developed across the collector to ground loop. Otherwise, that collector is seeing a very low Z into that autotransformer circuitry.)
:::::
:::::
:::::
:::::Consulting the schema , seems like no problem with speaker shunt switch (73) if you can get a thump from the unit.
:::::
:::::
:::::
:::::Assuredly with such a heat cooked unit thru the decades of July's and August's bakings , all of the red boxed electrolytics are due a Prev Maint replacement.
:::::
:::::
:::::
:::::Lastly, to make a dynamic operational test of the current gain of your output xstr, merely power up and take a 100 ohm resistor and a test lead and ground one clip end of the test lead and clip the other end onto one lead of the resistor and use the free end of the resistor to scratch….like a match…the base terminal of the DS-501, with a good unit a healthy “scratch” should come forth from the speaker. To test the DS-26 driver circuit, use the same procedure to its base, but use a 1K value of resistor instead.
:::::
:::::
:::::
:::::Standing by…..
:::::
:::::
:::::
:::::SCHEMATICUS REFERENCIMUS:
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::73's de Edd
:::::
:::::
Looking again at what's left of the label I see "73' " It looks like it may be part of a 1 but it's only the top half. It has an AM push button and and FM pushbutton. Between those two short buttons is the long wonderbar button.
Maybe if I took some pictures of it. Someone may recognize it. Also, I tried moving the mute switch and it makes no difference as far as I can tell. I'll look at that again too. This is taking way too long. I checked every land on that little board and can find no open lands. I find zero shorted lands. I flexed the board and no sound is heard. So it's still possible that the mute switch is muting the sound somewhere.
Thanks,
Dave
:Dave,
:
:The only Delco AM/FM/ WB radios I can find with a model number starting with "730" are the 1967 Olds model 7300103, and the 1968 Olds 7303173 and Toronado 7303243.
:
:All three use the same audio circuit, like the one I mentioned in my earlier post. Something else to check; since it is a signal seeker, there is also a "Mute" function added to silence the radio during "search". This operates through a contact/s on the search relay and the solenoid tied to the audio input stages.
:
:Meade
:
:
:
::MAG,
:: The 7303231 is an AM/FM, but it's not a stereo. It has a single DS-501 and a Single speaker connection. It's mono, unless, as you mentioned, a multiplex adaptor is used. Yes, the set that's not working or working very intermittently, is also an AM/FM Mono radio. It has a signal seeker too.
:: The two radios are almost identical. But the one that's not working doesn't have the multiplex jack. What remains of the model number looks like 730 but the rest is torn off.
:: I turned it on a little while ago and got the thump and it did work briefly but it refuses to work again. I don't know why it worked. That was the first time I had heard any sound at all from it.
::
::Thanks,
::
::Dave
:::Dave,
:::It would sure help if we knew exactly what model radio you're working on!!
:::
:::Your other working radio, model 7303231 is a 1968 Chevrolet AM/FM/Stereo radio. IF the problem radio is also an AM/FM/Stereo radio--- are you aware that it requires either the multiplex unit or a "jumper" plug to be installed for the radio to work? If there is a 9-pin socket on the back or side of the radio, it requires those.
:::
:::For reference, the 1968 Chevy AM/FM non-stereo (Corvette) is 7302721. Other 66, 67, 68, Delco AM/FM radios of that era that use the separate audio board are similar.
:::On this audio board, the two DS-66 driver transistors and the DS-501 are "direct coupled". Any problems with the driver circuits will upset the output. The 10mfd electrolytic coupling the audio from the volume control to the base of the first DS-66 is prone to going open.
:::
:::Maybe Edd will favor us with one of his great schematics to see if this is indeed the radio you have?
:::
:::No voltage on the collector and a .47 fuse resistor getting hot sounds to me like a shorted or very leaky DS-501 (I know you tried another one!), or a short or serious leak on the collector line. Double check the 1.5 ohm speaker choke and the output electrolytic, either a 4mfd or 15mfd for different 1968 Delco radios. Some of these radios also had a "spark plate" on the speaker line.
:::Also check along the feedback loop that is connected to the collector (1.8k and 8.2k resistors), leading back to the input of the audio amp circuit.
:::
:::Meade
:::
:::
:::
::::Edd,
:::: I just turned it on again today and it worked for about 12 seconds and then stopped. I turned off and on again, and it worked and stopped but will not turn on again. I tried another fuse resistor and it wont come on. The voltages I have on the base and emitter, not necessarily in this order 14.81 volts and 14.83 volts. My battery has a charger attached to it. I heard FM and it sounds great, if it would just stay on. My speaker connections are perfect. I can make the speaker "thump" using a 1.5 volt battery. This was the method used in the book to see if the speaker connections are good. There must be some intermittent connection on that small board. I will probably have to take it out and study it very closely. Maybe I have an intermittent resistor? Maybe a land on the board is intermittent. I have measured just about everything and the connections are perfect, as far as I can tell.
:::: This set is frustrating but somewhat more interesting that ones I usually see.
::::
::::Thanks,
::::
::::Dave
::::
::::
:::::Edd,
::::: This set has the three terminals in back labeled, + 12v, Speaker, and negative. It doesn't have the shorting switch. The transformer is located on this radio, not on the speaker. I have the book, "Practical Transistor servicing" By Bill Caldwell. This is the 1960 edition, the first edition. So I was pretty sure I knew this circuit. But occasionally I get a stumper like this. I have another set that's almost exactly the same and it works fine. Just a second, I'll get the model number of that. 7303231 is the model number of the working radio. It has the same small board with the volume control and audio section. I think that the schematic from that one would probably help with this one. I'll check everything some more this evening.
:::::
:::::Thanks,
:::::
:::::Dave
::::::
::::::
::::::
::::::
::::::
::::::
::::::I was just holding back and waiting for the other shoe to drop, as far as the circuitry design was concerned, as I was not ruling out the front end even utilizing low plate potential tubes in the front end and eventually feeding the AF driver transformer. But, with the forthcoming info, seems like an all xstr unit is the agreed upon design.
::::::
::::::
::::::If you willl consult with the schematic suggested, it just doesn’t agree with your being able to read a DYNAMIC 12 volt presence
::::::on the collector of the DS-501 such as you profess to be reading.
::::::
::::::You did not confirm if you have all of the unit…especially the factory speaker and its autotransformer design of low impedance A.F.output transformer.
::::::
::::::
::::::
::::::Looking at the 12 VDC power supply buss….. it comes upwards from the bottom and passes thru a .47 ohm emitter/fusible resistor and feeds the DS 501 emitter. Simultaneously there is 12VDC routed off to the left to the 10 ohm and 175 ohm voltage divider pair that establish the operational quiescent bias on the base of the ‘501.
::::::
::::::Item 36….1K… electrolytic provides low freq AC shunt bypassing for the stage.
::::::
::::::Lowering the resistance setting of item 74 …bias pot…increases the base bias…collector consumption..
::::::
::::::Soooooo …..with you having such an exorbitantly high collector voltage present, and considering stock speaker and output transformer connected up, it just seems that you must have an open somewhere from the blue buss from the collector to its eventual passage thru the output transformer and its final ground connection..
::::::
::::::
::::::
::::::(Now there is no chance that there is merely / solely a test speaker connected from DS-501 collector to ground,….is there ? as that could account for the possible higher voltage being able to be developed across the collector to ground loop. Otherwise, that collector is seeing a very low Z into that autotransformer circuitry.)
::::::
::::::
::::::
::::::Consulting the schema , seems like no problem with speaker shunt switch (73) if you can get a thump from the unit.
::::::
::::::
::::::
::::::Assuredly with such a heat cooked unit thru the decades of July's and August's bakings , all of the red boxed electrolytics are due a Prev Maint replacement.
::::::
::::::
::::::
::::::Lastly, to make a dynamic operational test of the current gain of your output xstr, merely power up and take a 100 ohm resistor and a test lead and ground one clip end of the test lead and clip the other end onto one lead of the resistor and use the free end of the resistor to scratch….like a match…the base terminal of the DS-501, with a good unit a healthy “scratch” should come forth from the speaker. To test the DS-26 driver circuit, use the same procedure to its base, but use a 1K value of resistor instead.
::::::
::::::
::::::
::::::Standing by…..
::::::
::::::
::::::
::::::SCHEMATICUS REFERENCIMUS:
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::73's de Edd
::::::
::::::
Since you now mentioned that the unit is an AM-FM, unit we will now switch to the model which you think is a dupe of the
unidentified unit that you are now working with.
And of course on the full info that I have on that chassis, no "Vunder Bar†tuning is involved in this models design..the 7303231.
Why don't you connect two clip leads across the .47 fusible resistor and connect onto DC voltmeter on its low scale and turn on the set and mmonitor the voltage reading if the set plays on turn on….and then wait for your 12 seconds and see what the shift in voltage reading is when the set goes off.
Additionally on looking at the new schematic….the mentioned 10 ufd coupling capacitor C6 from the center of the volume control coupling into the base of Q11, could account for the loss of audio feed thru the system…if that is actually the manner of failure mode BUT an equally suspect one additionally is the C8 emitter bypass capacitor of Q11.
If you are suspect of the loss of sound being due to the output stage you could inject a signal into the volume control to confirm that the loss is thru those final stages instead of the frontal stages.
Working Schematic:
73's de Edd
Yes, that looks almost exactly like the circuit. There is, for instance a 47 ohm resistor next to a 56 ohm resistor which is next to the fuse resistor. I have replaced all the capacitors you have highlighted in yellow. I'll measure the voltage. Maybe the radio will play now and maybe it wont. This model has a signal seeker. As MAG pointed out, maybe the mute switch (solenoid like relay) is stuck on.
Thanks,
Dave
The voltage across the fuse resistor is 0.00. The exact same voltage is on each end of the resistor.
:
:
:
:
:
:
:
:
:
:
:Since you now mentioned that the unit is an AM-FM, unit we will now switch to the model which you think is a dupe of the
:unidentified unit that you are now working with.
:
:
:And of course on the full info that I have on that chassis, no "Vunder Bar†tuning is involved in this models design..the 7303231.
:
:
:Why don't you connect two clip leads across the .47 fusible resistor and connect onto DC voltmeter on its low scale and turn on the set and mmonitor the voltage reading if the set plays on turn on….and then wait for your 12 seconds and see what the shift in voltage reading is when the set goes off.
:
:
:Additionally on looking at the new schematic….the mentioned 10 ufd coupling capacitor C6 from the center of the volume control coupling into the base of Q11, could account for the loss of audio feed thru the system…if that is actually the manner of failure mode BUT an equally suspect one additionally is the C8 emitter bypass capacitor of Q11.
:
:
:If you are suspect of the loss of sound being due to the output stage you could inject a signal into the volume control to confirm that the loss is thru those final stages instead of the frontal stages.
:
:
:
:
:Working Schematic:
:
:
:
:
:
:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
If you are reading zeeeeee-ro across that point 47 reee-sistor, that signifys that the transistor is not in CON-duction ……..soooooo…try the clipping in of your metering, such that you will then have all three hands free….. And then do the test that I suggested as per the test on the output xstr, by biasing it on an instant with the 100 ohm resistor with its negative voltage reference / source being acquired by its other side being grounded.
Say then, that in the most optimistic case , that you would be able to initiate a 1 amp collector current while in that mode, you would then be expecting in the
order of ~ 1 amp current thru that series emitter ….thus creating a reading of ~ 1/2 Vdc on your monitoring.
Should that test not be fruitful then we would then have to look at the DS-501 itself , and confirm that the red and blue lined wiring connections are not corrupted, by being open, or equally as suspect, a fault in the circuits direct coupled output base drive that is being acquired via the cascaded DS-26’s circuitry.
ZUJ’ing…for your findings……….
Working Schematic:
73's de Edd
:
:
:
:
:
:
:
:
:
:
:If you are reading zeeeeee-ro across that point 47 reee-sistor, that signifys that the transistor is not in CON-duction ……..soooooo…try the clipping in of your metering, such that you will then have all three hands free….. And then do the test that I suggested as per the test on the output xstr, by biasing it on an instant with the 100 ohm resistor with its negative voltage reference / source being acquired by its other side being grounded.
:
:
:Say then, that in the most optimistic case , that you would be able to initiate a 1 amp collector current while in that mode, you would then be expecting in the
:order of ~ 1 amp current thru that series emitter ….thus creating a reading of ~ 1/2 Vdc on your monitoring.
:
:
:Should that test not be fruitful then we would then have to look at the DS-501 itself , and confirm that the red and blue lined wiring connections are not corrupted, by being open, or equally as suspect, a fault in the circuits direct coupled output base drive that is being acquired via the cascaded DS-66’s circuitry.
:
:
:
:ZUJ’ing…for your findings……….
:
:
:
:Working Schematic:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:
Are you saying that we should short out R64?
Thanks,
Dave
::
::
::
::
::
::
::
::
::
::
::
::If you are reading zeeeeee-ro across that point 47 reee-sistor, that signifys that the transistor is not in CON-duction ……..soooooo…try the clipping in of your metering, such that you will then have all three hands free….. And then do the test that I suggested as per the test on the output xstr, by biasing it on an instant with the 100 ohm resistor with its negative voltage reference / source being acquired by its other side being grounded.
::
::
::Say then, that in the most optimistic case , that you would be able to initiate a 1 amp collector current while in that mode, you would then be expecting in the
::order of ~ 1 amp current thru that series emitter ….thus creating a reading of ~ 1/2 Vdc on your monitoring.
::
::
::Should that test not be fruitful then we would then have to look at the DS-501 itself , and confirm that the red and blue lined wiring connections are not corrupted, by being open, or equally as suspect, a fault in the circuits direct coupled output base drive that is being acquired via the cascaded DS-66’s circuitry.
::
::
::
::ZUJ’ing…for your findings……….
::
::
::
::Working Schematic:
::
::
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::
: Are you saying that we should short out R64?
:
:Thanks,
:
:Dave
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::If you are reading zeeeeee-ro across that point 47 reee-sistor, that signifys that the transistor is not in CON-duction ……..soooooo…try the clipping in of your metering, such that you will then have all three hands free….. And then do the test that I suggested as per the test on the output xstr, by biasing it on an instant with the 100 ohm resistor with its negative voltage reference / source being acquired by its other side being grounded.
:::
:::
:::Say then, that in the most optimistic case , that you would be able to initiate a 1 amp collector current while in that mode, you would then be expecting in the
:::order of ~ 1 amp current thru that series emitter ….thus creating a reading of ~ 1/2 Vdc on your monitoring.
:::
:::
:::Should that test not be fruitful then we would then have to look at the DS-501 itself , and confirm that the red and blue lined wiring connections are not corrupted, by being open, or equally as suspect, a fault in the circuits direct coupled output base drive that is being acquired via the cascaded DS-66’s circuitry.
:::
:::
:::
:::ZUJ’ing…for your findings……….
:::
:::
:::
:::Working Schematic:
:::
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::
:::Gentelmen: Dave, Meade& Edd : I'm Leo Cummings just been surfing the site and ran into your correspondence. I'm an old novice repairer and working on a 68 Pontiac am/fm with reverb & power antenna. Its out of my antique vehicle. I could use some help. Radio did not work in car now on my bench with two pieces and no schematic. Could not find on Delco listings. The radio-unit is Model#7303302 and the Aux-unit is Model#7304342. Could any of you offer me some help with the schematic Diagram & any addional info or recommendations per bench testing set up. I'v repaired several of my other 1966 Pontiac am/fm's one piece. Usually just a good cleaning of the Volume & Tone controls with spray cleaner dn shafts and gently clean and rotate the wire wound variable resistor in the amp circuit that has fused together to point where radio didn't work at all. SO ! Thats my story. I quess I should have tested this Submit before two finger typing this- oh well, here goes. Tks. Leo C.
:::
:::
:::
Are you asking me to short out R64? If not, then I don't understand what you are asking me to do. Maybe R64 is intermittent? The 100 ohm resistor gets very hot to the touch. It's so close to the fuse resistor that I couldn't tell. The fuse resistor stays cool but it doesn't seem to be open.
Thanks,
Dave
:
:
:
:
:
:
:
:
:
:
:
:If you are reading zeeeeee-ro across that point 47 reee-sistor, that signifys that the transistor is not in CON-duction ……..soooooo…try the clipping in of your metering, such that you will then have all three hands free….. And then do the test that I suggested as per the test on the output xstr, by biasing it on an instant with the 100 ohm resistor with its negative voltage reference / source being acquired by its other side being grounded.
:
:
:Say then, that in the most optimistic case , that you would be able to initiate a 1 amp collector current while in that mode, you would then be expecting in the
:order of ~ 1 amp current thru that series emitter ….thus creating a reading of ~ 1/2 Vdc on your monitoring.
:
:
:Should that test not be fruitful then we would then have to look at the DS-501 itself , and confirm that the red and blue lined wiring connections are not corrupted, by being open, or equally as suspect, a fault in the circuits direct coupled output base drive that is being acquired via the cascaded DS-26’s circuitry.
:
:
:
:ZUJ’ing…for your findings……….
:
:
:
:Working Schematic:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:
"Are you saying that we should short out R64? Thanks,Dave"
Nope, the testing that I mentioned is to be done completely with ANOTHER 100 ohm resistor that you temp touch into the base circuit as I had explained.
As per those resistor pair .. a 100 and a 56...on the emitter of the final driver, they ARE 1 and 2 watt units, since they inherently run a skosh warm.
Also, come back to us with the monitored voltages on all of the three involved transistors C,B and E's..... as that would be the next thing of interest in analyzing.
Your "fuse resistor" is coooool because there is no curent passing thru that loop in the sets current "in" operative condition of the output stage.
Working Schematic:
73's de Edd
I think I get it. Take a 100 ohm resistor, use a clip lead and connect one end to the chassis. Take the other end and touch it to the base of the transistor and see if it can turn on. But only do that for a second or three. I don't think I'll hear anything but I'll give it a try.
Thanks,
Dave
:
:
: "Are you saying that we should short out R64? Thanks,Dave"
:
:
:
:
:
:
:
:
:
:
:Nope, the testing that I mentioned is to be done completely with ANOTHER 100 ohm resistor that you temp touch into the base circuit as I had explained.
:
:
:As per those resistor pair .. a 100 and a 56...on the emitter of the final driver, they ARE 1 and 2 watt units, since they inherently run a skosh warm.
:
:
:Also, come back to us with the monitored voltages on all of the three involved transistors C,B and E's..... as that would be the next thing of interest in analyzing.
:Your "fuse resistor" is coooool because there is no curent passing thru that loop in the sets current "in" operative condition of the output stage.
:
:
:
:
:Working Schematic:
:
:
:
:
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:
:73's de Edd
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:
Yes, that, indeed, turns the transistor on but the sound is very faint, but it is on, the speaker cone makes a nice thump. It does stay on for a few seconds after I disconnect the resistor. Now what?
I would like to tell you the voltages on the other transistors, but without a diagram, I don't know which transistor is which. But I will get some readings without the 100 ohm test resistor in place. Maybe one of the other transistors is at fault?
Thanks,
Dave
:Edd,
:I think I get it. Take a 100 ohm resistor, use a clip lead and connect one end to the chassis. Take the other end and touch it to the base of the transistor and see if it can turn on. But only do that for a second or three. I don't think I'll hear anything but I'll give it a try.
:
:Thanks,
:
:Dave
::
::
:: "Are you saying that we should short out R64? Thanks,Dave"
::
::
::
::
::
::
::
::
::
::
::Nope, the testing that I mentioned is to be done completely with ANOTHER 100 ohm resistor that you temp touch into the base circuit as I had explained.
::
::
::As per those resistor pair .. a 100 and a 56...on the emitter of the final driver, they ARE 1 and 2 watt units, since they inherently run a skosh warm.
::
::
::Also, come back to us with the monitored voltages on all of the three involved transistors C,B and E's..... as that would be the next thing of interest in analyzing.
::Your "fuse resistor" is coooool because there is no curent passing thru that loop in the sets current "in" operative condition of the output stage.
::
::
::
::
::Working Schematic:
::
::
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::
::
The previous transistor's collector is connected to the base of the output transistor. So here are it's voltages with the DS-501 off:
Q12:
C: 12.38v
B: 7.11 v
E: 4.41v
Q11:
C: 7.11 v
B: 0.882v
E: 0.281 v
These don't seem right to me.
Where you have a reading of 11.8 v, I read 12.39 volts.
I added a 22K ohm resistor R62 because it appeared to be open. No reading at all, infinite. But I don't think that's what's causing this problem.
Thanks,
Dave
:
:
: "Are you saying that we should short out R64? Thanks,Dave"
:
:
:
:
:
:
:
:
:
:
:Nope, the testing that I mentioned is to be done completely with ANOTHER 100 ohm resistor that you temp touch into the base circuit as I had explained.
:
:
:As per those resistor pair .. a 100 and a 56...on the emitter of the final driver, they ARE 1 and 2 watt units, since they inherently run a skosh warm.
:
:
:Also, come back to us with the monitored voltages on all of the three involved transistors C,B and E's..... as that would be the next thing of interest in analyzing.
:Your "fuse resistor" is coooool because there is no curent passing thru that loop in the sets current "in" operative condition of the output stage.
:
:
:
:
:Working Schematic:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:
:
As per your higher power supply reading, possibly that is because you have your supply voltage set up a bit higher, try reducing it until that supply B+ voltage matches up with that figure.
BUT…. it seems that the problem is in the driver xstrs stage area, now try the same procedure as used in the output stage by utilizing to a 1k resistor and a quick touch to the base of Q12 to see if you get a healthy response from the speaker with a quick touch.
Then you move on down to the Q11 stage where you should get the healthiest response of all.
I have upwardly revised the working schema and the red numbers are yours. The bias on the emitter of Q11 is too low, can you trim in R2 pot to see if the voltage on that Q11 emitter can approach ~ point7 VDC ? If that R62 was open, it just must have given up the ghost due to quality / vibration/ thermal / interconnect fault(s), as it is not taxed in the circuit’s power demands.
Can you also vouch for the integrity of all of the resistors that I have highlighted in turquoise ?
Working Schematic:
73's de Edd
I have checked all the resistors you have highlighted in Torquoise. I replaced the 47 ohm resistor because it was open. Some I cannot tell if they are a problem. But these tests should be able to point out which one(s) is/are faulty, if it/they are intermittent. Maybe one has a hairline crack and that's why it's so intermittent. I also replaced one of the 22K ohm resistors, as I mentioned earlier.
I'll do my testing with a 1K ohm resistor. The output should be louder because the 2nd AF transistor should have a higher voltage on its collector.
I think I understand that with the two NPN transistors I cannot connect the 1K to negative and touch the base to turn it on. I think I have to connect one end of the 1K ohm resistor to + 12 volts because these are NPN transistors.
Thanks very much,
Dave
:
:
:
:
:
:
:
:
:
:As per your higher power supply reading, possibly that is because you have your supply voltage set up a bit higher, try reducing it until that supply B+ voltage matches up with that figure.
:
:
:BUT…. it seems that the problem is in the driver xstrs stage area, now try the same procedure as used in the output stage by utilizing to a 1k resistor and a quick touch to the base of Q12 to see if you get a healthy response from the speaker with a quick touch.
:Then you move on down to the Q11 stage where you should get the healthiest response of all.
:
:
:
:I have upwardly revised the working schema and the red numbers are yours. The bias on the emitter of Q11 is too low, can you trim in R2 pot to see if the voltage on that Q11 emitter can approach ~ point7 VDC ? If that R62 was open, it just must have given up the ghost due to quality / vibration/ thermal / interconnect fault(s), as it is not taxed in the circuit’s power demands.
:
:
:
:Can you also vouch for the integrity of all of the resistors that I have highlighted in turquoise ?
:
:
:Working Schematic:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:
:
I tried the test and it doesn't get any response whatsoever through the speaker. It only turns on Q13. I connected one end of the 1K resistor to the case of the radio and the other end to the base of Q12. I hear nothing at all through the speaker. I touched the other end to the base on Q11 and I heard nothing at all through the speaker. However when I touch the other end to the base of Q13, the speaker makes its thump and I hear hiss and sound. But the sound is weak. When it came on, for what reason I have no idea, the sound was nice and loud.
I can adjust the pot so that I can get .3 volts maximum. I'm not using a power supply. The radio is connected to a large 12 v car battery.
When I measure R63 in circuit it's about 65 ohms, not 100. Would that make any difference or is that a correct resistance reading when it's in circuit?
What should I look at next?
Thanks,
Dave
:
:
:
:
:
:
:
:
:
:As per your higher power supply reading, possibly that is because you have your supply voltage set up a bit higher, try reducing it until that supply B+ voltage matches up with that figure.
:
:
:BUT…. it seems that the problem is in the driver xstrs stage area, now try the same procedure as used in the output stage by utilizing to a 1k resistor and a quick touch to the base of Q12 to see if you get a healthy response from the speaker with a quick touch.
:Then you move on down to the Q11 stage where you should get the healthiest response of all.
:
:
:
:I have upwardly revised the working schema and the red numbers are yours. The bias on the emitter of Q11 is too low, can you trim in R2 pot to see if the voltage on that Q11 emitter can approach ~ point7 VDC ? If that R62 was open, it just must have given up the ghost due to quality / vibration/ thermal / interconnect fault(s), as it is not taxed in the circuit’s power demands.
:
:
:
:Can you also vouch for the integrity of all of the resistors that I have highlighted in turquoise ?
:
:
:Working Schematic:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:
:
I've tried it every possible way and a quick touch to the bases does nothing. It's as if I'm not touching anything. I don't see how it would turn on those transistors to have a lower voltage on the base than on the emitter, if it's an NPN transistor.
Thanks,
Dave
:Edd,
: I tried the test and it doesn't get any response whatsoever through the speaker. It only turns on Q13. I connected one end of the 1K resistor to the case of the radio and the other end to the base of Q12. I hear nothing at all through the speaker. I touched the other end to the base on Q11 and I heard nothing at all through the speaker. However when I touch the other end to the base of Q13, the speaker makes its thump and I hear hiss and sound. But the sound is weak. When it came on, for what reason I have no idea, the sound was nice and loud.
: I can adjust the pot so that I can get .3 volts maximum. I'm not using a power supply. The radio is connected to a large 12 v car battery.
: When I measure R63 in circuit it's about 65 ohms, not 100. Would that make any difference or is that a correct resistance reading when it's in circuit?
: What should I look at next?
:
:Thanks,
:
:Dave
::
::
::
::
::
::
::
::
::
::As per your higher power supply reading, possibly that is because you have your supply voltage set up a bit higher, try reducing it until that supply B+ voltage matches up with that figure.
::
::
::BUT…. it seems that the problem is in the driver xstrs stage area, now try the same procedure as used in the output stage by utilizing to a 1k resistor and a quick touch to the base of Q12 to see if you get a healthy response from the speaker with a quick touch.
::Then you move on down to the Q11 stage where you should get the healthiest response of all.
::
::
::
::I have upwardly revised the working schema and the red numbers are yours. The bias on the emitter of Q11 is too low, can you trim in R2 pot to see if the voltage on that Q11 emitter can approach ~ point7 VDC ? If that R62 was open, it just must have given up the ghost due to quality / vibration/ thermal / interconnect fault(s), as it is not taxed in the circuit’s power demands.
::
::
::
::Can you also vouch for the integrity of all of the resistors that I have highlighted in turquoise ?
::
::
::Working Schematic:
::
::
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::
::
This radio is still very frustrating. Do you think there's another open resistor?
Thanks,
Dave
:Edd,
: I've tried it every possible way and a quick touch to the bases does nothing. It's as if I'm not touching anything. I don't see how it would turn on those transistors to have a lower voltage on the base than on the emitter, if it's an NPN transistor.
:
:Thanks,
:
:Dave
::Edd,
:: I tried the test and it doesn't get any response whatsoever through the speaker. It only turns on Q13. I connected one end of the 1K resistor to the case of the radio and the other end to the base of Q12. I hear nothing at all through the speaker. I touched the other end to the base on Q11 and I heard nothing at all through the speaker. However when I touch the other end to the base of Q13, the speaker makes its thump and I hear hiss and sound. But the sound is weak. When it came on, for what reason I have no idea, the sound was nice and loud.
:: I can adjust the pot so that I can get .3 volts maximum. I'm not using a power supply. The radio is connected to a large 12 v car battery.
:: When I measure R63 in circuit it's about 65 ohms, not 100. Would that make any difference or is that a correct resistance reading when it's in circuit?
:: What should I look at next?
::
::Thanks,
::
::Dave
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::As per your higher power supply reading, possibly that is because you have your supply voltage set up a bit higher, try reducing it until that supply B+ voltage matches up with that figure.
:::
:::
:::BUT…. it seems that the problem is in the driver xstrs stage area, now try the same procedure as used in the output stage by utilizing to a 1k resistor and a quick touch to the base of Q12 to see if you get a healthy response from the speaker with a quick touch.
:::Then you move on down to the Q11 stage where you should get the healthiest response of all.
:::
:::
:::
:::I have upwardly revised the working schema and the red numbers are yours. The bias on the emitter of Q11 is too low, can you trim in R2 pot to see if the voltage on that Q11 emitter can approach ~ point7 VDC ? If that R62 was open, it just must have given up the ghost due to quality / vibration/ thermal / interconnect fault(s), as it is not taxed in the circuit’s power demands.
:::
:::
:::
:::Can you also vouch for the integrity of all of the resistors that I have highlighted in turquoise ?
:::
:::
:::Working Schematic:
:::
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::
:::
:::
:::
:::
:::
Most honnable apologies….. been TOTALLY electronically incommunicado for past week-end. Even the phone utilized a hand crank ringer.
Oops…….. when we reverted from the initial circuit using a driver transformer and the PNP driver transistor…and now …..with the circuitry using a direct drive coupled circuit with its tandem devices, I neglected to carry forward and then mention that the biasing manner of them would
then be with the application of POSITIVE bias from the 12dc supply and that being thru a thru a 1K current limiting resistor to either of those bases, which you seem to have caught but apparently did not follow thru in doing it that way, of course the DS501 responded properly , with it having the proper biasing being applied to it.
Fortunately the driver transistors are silicon technology versus the old "geranium' type which the output xstr is using.
If they would have been germanium, with time and heat , their leakage factor should have shifted to a horrific value by now.
You might additionally pull the '66's and check their CBE junctions out with a common analog ohmmeter, or possibly, you might have one of the DVM's with the additional bonus of a transistor test function thrown in as one of its additional features.
The '66's test like the common ECG / NTE, run of the mill. G Purp ECG 123.
Working Schematic:
73's de Edd
I did try 12v through a 1K resistor and it didn't do anything. Nothing came on. So if it takes ECG or NTE 123s, or maybe a Radio Shack transistor, I could try one or both of them and see if it works. But anyway, this is getting very frustrating.
Thanks,
Dave
:
:
:
:
:
:
:
:
:
:Most honnable apologies….. been TOTALLY electronically incommunicado for past week-end. Even the phone utilized a hand crank ringer.
:
:
:Oops…….. when we reverted from the initial circuit using a driver transformer and the PNP driver transistor…and now …..with the circuitry using a direct drive coupled circuit with its tandem devices, I neglected to carry forward and then mention that the biasing manner of them would
:then be with the application of POSITIVE bias from the 12dc supply and that being thru a thru a 1K current limiting resistor to either of those bases, which you seem to have caught but apparently did not follow thru in doing it that way, of course the DS501 responded properly , with it having the proper biasing being applied to it.
:
:Fortunately the driver transistors are silicon technology versus the old "geranium' type which the output xstr is using.
:If they would have been germanium, with time and heat , their leakage factor should have shifted to a horrific value by now.
:
:You might additionally pull the '66's and check their CBE junctions out with a common analog ohmmeter, or possibly, you might have one of the DVM's with the additional bonus of a transistor test function thrown in as one of its additional features.
:
:The '66's test like the common ECG / NTE, run of the mill. G Purp ECG 123.
:
:
:
:
:Working Schematic:
:
:
:
:
:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
I just revisited this radio again. It's still driving me nuts. Now on Q11 I have:
C: 12.35 v
E: .038 v
B: .5 v
I have checked all the resistor and zero of them are open. I'm looking at the tiny board where that the volume/tone control is soldered to.
This is still extremely frustrating. There must be something connected wrong. But I cannot see it. I will attempt to control my frustration as I continue to work on this set.
What should I check now?
There is no 1.5 volts on the collector of the DS-501. If I connect a battery there I can make the speaker thump. But that accomplishes nothing.
I tried what you wanted me to do and had sound. The radio seemed to work. I'll look through try that again. I forgot exactly what it was. But the volume was very weak when I did that. What did that indicate. I don't think that Q11 is turning on.
What should I check now?
Thanks,
Dave
:Edd,
: The previous transistor's collector is connected to the base of the output transistor. So here are it's voltages with the DS-501 off:
:
:Q12:
:C: 12.38v
:B: 7.11 v
:E: 4.41v
:
:Q11:
:C: 7.11 v
:B: 0.882v
:E: 0.281 v
:
:These don't seem right to me.
:
:Where you have a reading of 11.8 v, I read 12.39 volts.
:
:I added a 22K ohm resistor R62 because it appeared to be open. No reading at all, infinite. But I don't think that's what's causing this problem.
:
:Thanks,
:
:Dave
::
::
:: "Are you saying that we should short out R64? Thanks,Dave"
::
::
::
::
::
::
::
::
::
::
::Nope, the testing that I mentioned is to be done completely with ANOTHER 100 ohm resistor that you temp touch into the base circuit as I had explained.
::
::
::As per those resistor pair .. a 100 and a 56...on the emitter of the final driver, they ARE 1 and 2 watt units, since they inherently run a skosh warm.
::
::
::Also, come back to us with the monitored voltages on all of the three involved transistors C,B and E's..... as that would be the next thing of interest in analyzing.
::Your "fuse resistor" is coooool because there is no curent passing thru that loop in the sets current "in" operative condition of the output stage.
::
::
::
::
::Working Schematic:
::
::
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::
::
I just revisited this radio again. It's still driving me nuts. Now on Q11 I have:
C: 12.35 v
E: .038 v
B: .5 v
I have checked all the resistor and zero of them are open. I'm looking at the tiny board where that the volume/tone control is soldered to.
This is still extremely frustrating. There must be something connected wrong. But I cannot see it. I will attempt to control my frustration as I continue to work on this set.
What should I check now?
There is no 1.5 volts on the collector of the DS-501. If I connect a battery there I can make the speaker thump. But that accomplishes nothing.
I tried what you wanted me to do and had sound. The radio seemed to work. I'll look through try that again. I forgot exactly what it was. But the volume was very weak when I did that. What did that indicate. I don't think that Q11 is turning on.
What should I check now?
Thanks,
Dave
:Edd,
: The previous transistor's collector is connected to the base of the output transistor. So here are it's voltages with the DS-501 off:
:
:Q12:
:C: 12.38v
:B: 7.11 v
:E: 4.41v
:
:Q11:
:C: 7.11 v
:B: 0.882v
:E: 0.281 v
:
:These don't seem right to me.
:
:Where you have a reading of 11.8 v, I read 12.39 volts.
:
:I added a 22K ohm resistor R62 because it appeared to be open. No reading at all, infinite. But I don't think that's what's causing this problem.
:
:Thanks,
:
:Dave
::
::
:: "Are you saying that we should short out R64? Thanks,Dave"
::
::
::
::
::
::
::
::
::
::
::Nope, the testing that I mentioned is to be done completely with ANOTHER 100 ohm resistor that you temp touch into the base circuit as I had explained.
::
::
::As per those resistor pair .. a 100 and a 56...on the emitter of the final driver, they ARE 1 and 2 watt units, since they inherently run a skosh warm.
::
::
::Also, come back to us with the monitored voltages on all of the three involved transistors C,B and E's..... as that would be the next thing of interest in analyzing.
::Your "fuse resistor" is coooool because there is no curent passing thru that loop in the sets current "in" operative condition of the output stage.
::
::
::
::
::Working Schematic:
::
::
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::
::
Yes, when I use the 100 ohm resistor connected on one end to the chassis and the other end to the Base of the the DS-501, the transistor turns on and I can faintly hear the radio playing. But that's as far as I can get. Where exactly does the 1.5 volts come from? It seems to me that it comes from the main board somewhere. Or does it come from one of the resistors or voltage divider connected to the " 11.8" volt line? Maybe when the DS-501 is on, there is 1.5 volts on the collector coming from the transistor. I have no idea. This always confuses me.
I would like to solve this problem tonight. I've had it with this set. It should work but it doesn't. I heard it play for about 12 seconds one day many months ago, somehow. It sounded fantastic too! But now something that I can't find is preventing this set from working.
So please help if you can.
Thanks,
Dave
:Edd,
: I just revisited this radio again. It's still driving me nuts. Now on Q11 I have:
:
:C: 12.35 v
:E: .038 v
:B: .5 v
:
:I have checked all the resistor and zero of them are open. I'm looking at the tiny board where that the volume/tone control is soldered to.
:
:This is still extremely frustrating. There must be something connected wrong. But I cannot see it. I will attempt to control my frustration as I continue to work on this set.
:
:What should I check now?
:
:There is no 1.5 volts on the collector of the DS-501. If I connect a battery there I can make the speaker thump. But that accomplishes nothing.
:
:I tried what you wanted me to do and had sound. The radio seemed to work. I'll look through try that again. I forgot exactly what it was. But the volume was very weak when I did that. What did that indicate. I don't think that Q11 is turning on.
:
:What should I check now?
:
:Thanks,
:
:Dave
:
::Edd,
:: The previous transistor's collector is connected to the base of the output transistor. So here are it's voltages with the DS-501 off:
::
::Q12:
::C: 12.38v
::B: 7.11 v
::E: 4.41v
::
::Q11:
::C: 7.11 v
::B: 0.882v
::E: 0.281 v
::
::These don't seem right to me.
::
::Where you have a reading of 11.8 v, I read 12.39 volts.
::
::I added a 22K ohm resistor R62 because it appeared to be open. No reading at all, infinite. But I don't think that's what's causing this problem.
::
::Thanks,
::
::Dave
:::
:::
::: "Are you saying that we should short out R64? Thanks,Dave"
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::Nope, the testing that I mentioned is to be done completely with ANOTHER 100 ohm resistor that you temp touch into the base circuit as I had explained.
:::
:::
:::As per those resistor pair .. a 100 and a 56...on the emitter of the final driver, they ARE 1 and 2 watt units, since they inherently run a skosh warm.
:::
:::
:::Also, come back to us with the monitored voltages on all of the three involved transistors C,B and E's..... as that would be the next thing of interest in analyzing.
:::Your "fuse resistor" is coooool because there is no curent passing thru that loop in the sets current "in" operative condition of the output stage.
:::
:::
:::
:::
:::Working Schematic:
:::
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::
:::
:::
:::
:::
:::
I'm going to try replacing the DS-66s. However I don't think it will make any difference.
I'll let everyone know what happened.
Thanks,
Dave
:Edd and All,
: Yes, when I use the 100 ohm resistor connected on one end to the chassis and the other end to the Base of the the DS-501, the transistor turns on and I can faintly hear the radio playing. But that's as far as I can get. Where exactly does the 1.5 volts come from? It seems to me that it comes from the main board somewhere. Or does it come from one of the resistors or voltage divider connected to the " 11.8" volt line? Maybe when the DS-501 is on, there is 1.5 volts on the collector coming from the transistor. I have no idea. This always confuses me.
: I would like to solve this problem tonight. I've had it with this set. It should work but it doesn't. I heard it play for about 12 seconds one day many months ago, somehow. It sounded fantastic too! But now something that I can't find is preventing this set from working.
: So please help if you can.
:
:Thanks,
:
:Dave
:
::Edd,
:: I just revisited this radio again. It's still driving me nuts. Now on Q11 I have:
::
::C: 12.35 v
::E: .038 v
::B: .5 v
::
::I have checked all the resistor and zero of them are open. I'm looking at the tiny board where that the volume/tone control is soldered to.
::
::This is still extremely frustrating. There must be something connected wrong. But I cannot see it. I will attempt to control my frustration as I continue to work on this set.
::
::What should I check now?
::
::There is no 1.5 volts on the collector of the DS-501. If I connect a battery there I can make the speaker thump. But that accomplishes nothing.
::
::I tried what you wanted me to do and had sound. The radio seemed to work. I'll look through try that again. I forgot exactly what it was. But the volume was very weak when I did that. What did that indicate. I don't think that Q11 is turning on.
::
::What should I check now?
::
::Thanks,
::
::Dave
::
:::Edd,
::: The previous transistor's collector is connected to the base of the output transistor. So here are it's voltages with the DS-501 off:
:::
:::Q12:
:::C: 12.38v
:::B: 7.11 v
:::E: 4.41v
:::
:::Q11:
:::C: 7.11 v
:::B: 0.882v
:::E: 0.281 v
:::
:::These don't seem right to me.
:::
:::Where you have a reading of 11.8 v, I read 12.39 volts.
:::
:::I added a 22K ohm resistor R62 because it appeared to be open. No reading at all, infinite. But I don't think that's what's causing this problem.
:::
:::Thanks,
:::
:::Dave
::::
::::
:::: "Are you saying that we should short out R64? Thanks,Dave"
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::Nope, the testing that I mentioned is to be done completely with ANOTHER 100 ohm resistor that you temp touch into the base circuit as I had explained.
::::
::::
::::As per those resistor pair .. a 100 and a 56...on the emitter of the final driver, they ARE 1 and 2 watt units, since they inherently run a skosh warm.
::::
::::
::::Also, come back to us with the monitored voltages on all of the three involved transistors C,B and E's..... as that would be the next thing of interest in analyzing.
::::Your "fuse resistor" is coooool because there is no curent passing thru that loop in the sets current "in" operative condition of the output stage.
::::
::::
::::
::::
::::Working Schematic:
::::
::::
::::
::::
::::
::::
::::
::::73's de Edd
::::
::::
::::
::::
::::
::::
::::
I replaced Q11 and it made no difference. Then I replaced Q12 and Voila it's working "as if by magic".
I have no idea why I was so hesitant to replace them at first.
Now to check the Wonderbar in this set.
Thanks very very much,
Dave
:Edd and All,
: I'm going to try replacing the DS-66s. However I don't think it will make any difference.
: I'll let everyone know what happened.
:
:Thanks,
:
:Dave
:
::Edd and All,
:: Yes, when I use the 100 ohm resistor connected on one end to the chassis and the other end to the Base of the the DS-501, the transistor turns on and I can faintly hear the radio playing. But that's as far as I can get. Where exactly does the 1.5 volts come from? It seems to me that it comes from the main board somewhere. Or does it come from one of the resistors or voltage divider connected to the " 11.8" volt line? Maybe when the DS-501 is on, there is 1.5 volts on the collector coming from the transistor. I have no idea. This always confuses me.
:: I would like to solve this problem tonight. I've had it with this set. It should work but it doesn't. I heard it play for about 12 seconds one day many months ago, somehow. It sounded fantastic too! But now something that I can't find is preventing this set from working.
:: So please help if you can.
::
::Thanks,
::
::Dave
::
:::Edd,
::: I just revisited this radio again. It's still driving me nuts. Now on Q11 I have:
:::
:::C: 12.35 v
:::E: .038 v
:::B: .5 v
:::
:::I have checked all the resistor and zero of them are open. I'm looking at the tiny board where that the volume/tone control is soldered to.
:::
:::This is still extremely frustrating. There must be something connected wrong. But I cannot see it. I will attempt to control my frustration as I continue to work on this set.
:::
:::What should I check now?
:::
:::There is no 1.5 volts on the collector of the DS-501. If I connect a battery there I can make the speaker thump. But that accomplishes nothing.
:::
:::I tried what you wanted me to do and had sound. The radio seemed to work. I'll look through try that again. I forgot exactly what it was. But the volume was very weak when I did that. What did that indicate. I don't think that Q11 is turning on.
:::
:::What should I check now?
:::
:::Thanks,
:::
:::Dave
:::
::::Edd,
:::: The previous transistor's collector is connected to the base of the output transistor. So here are it's voltages with the DS-501 off:
::::
::::Q12:
::::C: 12.38v
::::B: 7.11 v
::::E: 4.41v
::::
::::Q11:
::::C: 7.11 v
::::B: 0.882v
::::E: 0.281 v
::::
::::These don't seem right to me.
::::
::::Where you have a reading of 11.8 v, I read 12.39 volts.
::::
::::I added a 22K ohm resistor R62 because it appeared to be open. No reading at all, infinite. But I don't think that's what's causing this problem.
::::
::::Thanks,
::::
::::Dave
:::::
:::::
::::: "Are you saying that we should short out R64? Thanks,Dave"
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::Nope, the testing that I mentioned is to be done completely with ANOTHER 100 ohm resistor that you temp touch into the base circuit as I had explained.
:::::
:::::
:::::As per those resistor pair .. a 100 and a 56...on the emitter of the final driver, they ARE 1 and 2 watt units, since they inherently run a skosh warm.
:::::
:::::
:::::Also, come back to us with the monitored voltages on all of the three involved transistors C,B and E's..... as that would be the next thing of interest in analyzing.
:::::Your "fuse resistor" is coooool because there is no curent passing thru that loop in the sets current "in" operative condition of the output stage.
:::::
:::::
:::::
:::::
:::::Working Schematic:
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::73's de Edd
:::::
:::::
:::::
:::::
:::::
:::::
:::::