Hello All,
I hope this 70s (late 60s?) radio isn't too new. The audio from the tuner is weak. The main amplifier is working ok. This radio has a very good tone to it. I do not have TSM-76, which is where the service data is. I assume that there's a capacitor at fault. But without seeing the schematic, I can only guess.
This is a multi band radio AM FM 2 SW bands and a longwave band. Everything works except directly before the main amp. If someone has seen this problem before please help. If I find the culpret, I'll let every one know that too.

Thanks for your help,

Dave

Hello Again,
I looked at the solder side of the board with the IF transformers on it and touched something (not sure what) and instantly the sound went to a normal level. So there's probably a tiny crack in the solder or a land that I cannnot find or get to disconnect again. No matter what I do, I cannot get it to stop working again.
Someone has unaligned the FM oscillator. 94 is where 88 should be. The same problem is on the other end. 106 is where 108 should be. So it cannot tune the entire band, just the middle of it. Everything is all spread out. Without the service data I do not know which coil is which. So please help if you can.

Thanks,

Dave
:Hello All,
: I hope this 70s (late 60s?) radio isn't too new. The audio from the tuner is weak. The main amplifier is working ok. This radio has a very good tone to it. I do not have TSM-76, which is where the service data is. I assume that there's a capacitor at fault. But without seeing the schematic, I can only guess.
: This is a multi band radio AM FM 2 SW bands and a longwave band. Everything works except directly before the main amp. If someone has seen this problem before please help. If I find the culpret, I'll let every one know that too.
:
:Thanks for your help,
:
:Dave

Dave
:Hello All,
: I hope this 70s (late 60s?) radio isn't too new. The audio from the tuner is weak. The main amplifier is working ok. This radio has a very good tone to it. I do not have TSM-76, which is where the service data is. I assume that there's a capacitor at fault. But without seeing the schematic, I can only guess.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hopefully, I can dig for that only moderately oldie for you, over this week end
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
: This is a multi band radio AM FM 2 SW bands and a longwave band. Everything works except directly before the main amp. If someone has seen this problem before please help. If I find the culpret, I'll let every one know that too.
:
:Thanks for your help,
:
:Dave

Hello Again,
I looked at the solder side of the board with the IF transformers on it and touched something (not sure what) and instantly the sound went to a normal level. So there's probably a tiny crack in the solder or a land that I cannnot find or get to disconnect again. No matter what I do, I cannot get it to stop working again as it should be. So it cannot tune the entire band, just the middle of it. Everything is all spread out. Without the service data I do not know which coil is which. So please help if you can.
Thanks,

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Not having pulled the tech data yet, is that a small table model or a small portable unit sizing ?

If using a small hand held PCB, will a corner to corner skew / twisting of the board show up your fault again ?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Someone has unaligned the FM oscillator. 94 is where 88 should be. The same problem is on the other end. 106 is where 108
should be. So it cannot tune the entire band, just the middle of it. Everything is all spread out. Without the service data I do not know which coil is which. So please help if you can.
Thanks,

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

With that degree of compression along with the nonlinearity, it would indicate a greater error in the L portion of the osc ckt L-C constants with the L being the greatest in error. This vintage of set was probably on the borderline of its utilization of the old familiar tuning capacitor. If a table model, possibly still using the air dielectric design of variable capacitor, but if a portable, the much smaller mylar spaced unit. Either way you can evaluate by just tuning into a moderate strength FM station and taking a screwdriver blade and merely sequentially touching the 4 options of connections to the variable cap. Two being for AM band RF and osc cap sections.The other two being, the of interest, RF and OSC sections for the FM band. When you hit the FM RF secton it might make a minumal volume shift, but when you touch the Osc section it will skew way off frequency. Thus you have found the FM osc section trimmer adj. If it was the air variable you could have merely visually ascertained by that sections miniscule plate sizing and count.
Its companion osc coil probably will be a coil formless air wound unit possibly waxed, and in that manner alone you typically could ascertain the "tampering" of the integrity of the factory wax layer. Typically tuning on that osc coil is done by inter turn wedging and skewing of its turns with an insulated / tapered "tuning / orange stick". Closer turns, more inductance ..further apart turns create less inductance. Thus producing Lower frequency of osc / higher frequency of the FM sectoins local oscillator.
The locating of the FM osc coil was done in a like manner, tuning into a FM staton and using stray finger tip capactance as you touch the ..only other coil of that dimensions. The osc will shift the station tuning wildly or easily shift tuning off the station when touching the coil. So there, you now have both the L and C elements located.

In the end, attain proper tracking by using the RF capacitance trimmer to bring in your high end of the band dial calibration references, the change of the osc coil inductance swings the low end of the band calibration. You will have to make several adjustments while running back to each ends of the dial references, since they inter-react. Then they should fall in , that is, within the toleraces of those tiny micro spaced out dial numbers, along with RF parts tolerances.

A final error could be if the FM if's were tweaked, but they desensitize rapidly with misadjustment.....sooooo.. if good reception sensitivity is present, they typically would not have been touched. Plus, most are small wax sealed slugs so the visual tampering with of that wax seal might confirm that situation..
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

73's de Edd

Edd,
There is, in fact, a large sized tuning capacitor enclosed in a metal box. I had not opened the box until now. Inside the box is another pc board with some adjustment capacitors. These are the controls I was looking for. However, this is the arrangement where one tunes the left side and the other tunes the right side of the band. I'll have guess. Adjusting one of them. I have more at the lower end of the band but the upper end goes past 108 and 105 is where 108 should be. When I get108 where it should be, then I don't have the low frequencies where they should be. This is odd but probably correct for the way it's adjusted, or mis-adjusted. This is too confusing and too frustrating without the service data I have no idea what to turn. All I can do is shift the stretched band one way or the other. I can even make 108 appear at 88. Then 95 is at 108.
I finally got it. How I did, I have no idea. Now 88 is where 88 should be and 108 is where it should be. That's it. I wont touch it again.
AFC didn't appear to work either. Now it does. I must have given it the magic touch.

Thanks for having me look a little farther (further?).

:Dave
The tone is fantastic. Maybe it's all an illusion.

::Hello All,
:: I hope this 70s (late 60s?) radio isn't too new. The audio from the tuner is weak. The main amplifier is working ok. This radio has a very good tone to it. I do not have TSM-76, which is where the service data is. I assume that there's a capacitor at fault. But without seeing the schematic, I can only guess.
:
:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
: Hopefully, I can dig for that only moderately oldie for you, over this week end
:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:: This is a multi band radio AM FM 2 SW bands and a longwave band. Everything works except directly before the main amp. If someone has seen this problem before please help. If I find the culpret, I'll let every one know that too.
::
::Thanks for your help,
::
::Dave
:
:
:Hello Again,
:I looked at the solder side of the board with the IF transformers on it and touched something (not sure what) and instantly the sound went to a normal level. So there's probably a tiny crack in the solder or a land that I cannnot find or get to disconnect again. No matter what I do, I cannot get it to stop working again as it should be. So it cannot tune the entire band, just the middle of it. Everything is all spread out. Without the service data I do not know which coil is which. So please help if you can.
:Thanks,
:
:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:Not having pulled the tech data yet, is that a small table model or a small portable unit sizing ?
:
:If using a small hand held PCB, will a corner to corner skew / twisting of the board show up your fault again ?
:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:
:
:Someone has unaligned the FM oscillator. 94 is where 88 should be. The same problem is on the other end. 106 is where 108
:should be. So it cannot tune the entire band, just the middle of it. Everything is all spread out. Without the service data I do not know which coil is which. So please help if you can.
:Thanks,
:
:
:
:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:
:With that degree of compression along with the nonlinearity, it would indicate a greater error in the L portion of the osc ckt L-C constants with the L being the greatest in error. This vintage of set was probably on the borderline of its utilization of the old familiar tuning capacitor. If a table model, possibly still using the air dielectric design of variable capacitor, but if a portable, the much smaller mylar spaced unit. Either way you can evaluate by just tuning into a moderate strength FM station and taking a screwdriver blade and merely sequentially touching the 4 options of connections to the variable cap. Two being for AM band RF and osc cap sections.The other two being, the of interest, RF and OSC sections for the FM band. When you hit the FM RF secton it might make a minumal volume shift, but when you touch the Osc section it will skew way off frequency. Thus you have found the FM osc section trimmer adj. If it was the air variable you could have merely visually ascertained by that sections miniscule plate sizing and count.
:Its companion osc coil probably will be a coil formless air wound unit possibly waxed, and in that manner alone you typically could ascertain the "tampering" of the integrity of the factory wax layer. Typically tuning on that osc coil is done by inter turn wedging and skewing of its turns with an insulated / tapered "tuning / orange stick". Closer turns, more inductance ..further apart turns create less inductance. Thus producing Lower frequency of osc / higher frequency of the FM sectoins local oscillator.
:The locating of the FM osc coil was done in a like manner, tuning into a FM staton and using stray finger tip capactance as you touch the ..only other coil of that dimensions. The osc will shift the station tuning wildly or easily shift tuning off the station when touching the coil. So there, you now have both the L and C elements located.
:
:In the end, attain proper tracking by using the RF capacitance trimmer to bring in your high end of the band dial calibration references, the change of the osc coil inductance swings the low end of the band calibration. You will have to make several adjustments while running back to each ends of the dial references, since they inter-react. Then they should fall in , that is, within the toleraces of those tiny micro spaced out dial numbers, along with RF parts tolerances.
:
:A final error could be if the FM if's were tweaked, but they desensitize rapidly with misadjustment.....sooooo.. if good reception sensitivity is present, they typically would not have been touched. Plus, most are small wax sealed slugs so the visual tampering with of that wax seal might confirm that situation..
:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:
:73's de Edd
:

OHHHHHH now with your further description , looks like you ran into one of the separately built complete FM tuner asssembly ion its cast pot metal encasment and
your compensation for the low band on that style of unit was still a variance of the L value of the oscillator coil. BUT, it seems like that unity used an osc coil wound on a form and is vertical mount with access thru a hole and by virtue of the miniscule tuning swing required at that freq it was using either a brass or aluminum...probably cross slotted....slug.
So you must have found it..with the other unit being the RF inductor. You could still differentiate by the tip of an 1/8 ion screwdriver down into the coil cavity
to skew the osc's operating frequency off.
Will still Really-search for your data this week end also.
73's de Edd

Dave
The tone is fantastic. Maybe it's all an illusion.

Sir David:

Nope , not magic, but all done with Smoke and Mirrors, along with a little Foo-Foo dust thrown in for good measure

Pulled your info on your Bulova with its 1200 Jewels and a Westminster movement. It was just as surmised on the osc coil construction, but not having the tuner built up in the pot metal housing.
Check yoah mails, for all tech info and alignment
data that was sent 2 U.

73's de Edd

Edd,
Audio has become weak again. I cannot seem to return it to normal. The main amp seems to work fine. When I hear a strong station on FM, If I take a 1 micro farad capacitor and attach (this doesn't make any sense) it across the 100 K resisor (R21) music is blasting through the speaker. What that has to do with Q8 I have no idea. I'm not sure Q8 is turned on though. It's difficult to tell which connection is which on that board. I can also find and connect sound directly to the input of the amplifier (through a DC blocking capacitor, of course). I'm using the amplifier as a signal tracer. I feel like I'm going around in circles finding the same thing over and over.
What should I try next? It seems like whatever component was awake, is asleep again. Is there a close up picture of the board with Q8 on it? A good picture of the solder side may help.
This is extremely frustrating. But if I can find where the problem is, this radio sounds fantastic.

Thanks,

:Dave
:The tone is fantastic. Maybe it's all an illusion.
:
:Sir David:
:
:Nope , not magic, but all done with Smoke and Mirrors, along with a little Foo-Foo dust thrown in for good measure
:
:Pulled your info on your Bulova with its 1200 Jewels and a Westminster movement. It was just as surmised on the osc coil construction, but not having the tuner built up in the pot metal housing.
:Check yoah mails, for all tech info and alignment
:data that was sent 2 U.
:
:
:73's de Edd

Sounds like the caps on rush charge is upsetting the
sets -5VDC supply. Your R21 is establishing a referece voltage against the AM AVC line. Therefore, be sure that there are no dried out / intermittent electrolytic caps in that -5 VDCsupply.

73's de Edd

Edd,
I replaced a 10 mf capacitor and two 2.2 mf capacitors and it made absolutely no difference. I can still find loud FM audio elswhere on the board. This is extremely frustrating. There are no markings on the teeny tiny overcrowded board. So I have no idea where I am hearing this audio. I'm listening using the main amp as a signal tracer through a capacitor to block DC. I can't leave it that way because AM Broadcast sound does't come from there. Also it's a pont where a diode is connected to one of the leads on a transistor. I can't find this on the schematic. I can find 3 diodes and none of them connect to a transistor.
Where to check next?

Thanks,

Dave
:Sounds like the caps on rush charge is upsetting the
:sets -5VDC supply. Your R21 is establishing a referece voltage against the AM AVC line. Therefore, be sure that there are no dried out / intermittent electrolytic caps in that -5 VDCsupply.
:
:73's de Edd

Edd,
I found it. That's X3 (AGC diode) attached to the emmiter on Q6 where I hear the loud FM. I don't hear any loud sound on the collector If it IS the collector). This is nowhere near the detetctors. Why am I hearing anything here at all? I'm wrong I do here the broadcast band at this point. I can't just leave this connected this way. I would really like to find where this problem is. I hope it's not inside one of the IF transformers.

Thanks,

Dave
:Edd,
: I replaced a 10 mf capacitor and two 2.2 mf capacitors and it made absolutely no difference. I can still find loud FM audio elswhere on the board. This is extremely frustrating. There are no markings on the teeny tiny overcrowded board. So I have no idea where I am hearing this audio. I'm listening using the main amp as a signal tracer through a capacitor to block DC. I can't leave it that way because AM Broadcast sound does't come from there. Also it's a pont where a diode is connected to one of the leads on a transistor. I can't find this on the schematic. I can find 3 diodes and none of them connect to a transistor.
: Where to check next?
:
:Thanks,
:
:Dave
::Sounds like the caps on rush charge is upsetting the
::sets -5VDC supply. Your R21 is establishing a referece voltage against the AM AVC line. Therefore, be sure that there are no dried out / intermittent electrolytic caps in that -5 VDCsupply.
::
::73's de Edd

Edd,
I accidently spelled hear wrong. I spelled it "here". I do hear the broadcast band AM at that point where X3 and Q6s emmitter connect. This AGC point is not the correct place to listen. If Q6 is working correctly, limiting the signal, with the limiting diode, then the problem must be somewhere else. The audio is very faint where it's actually supposed to be. Maybe one of the disc capacitors is open?

Dave
:Edd,
: I found it. That's X3 (AGC diode) attached to the emmiter on Q6 where I hear the loud FM. I don't hear any loud sound on the collector If it IS the collector). This is nowhere near the detetctors. Why am I hearing anything here at all? I'm wrong I do here the broadcast band at this point. I can't just leave this connected this way. I would really like to find where this problem is. I hope it's not inside one of the IF transformers.
:
:Thanks,
:
:Dave
::Edd,
:: I replaced a 10 mf capacitor and two 2.2 mf capacitors and it made absolutely no difference. I can still find loud FM audio elswhere on the board. This is extremely frustrating. There are no markings on the teeny tiny overcrowded board. So I have no idea where I am hearing this audio. I'm listening using the main amp as a signal tracer through a capacitor to block DC. I can't leave it that way because AM Broadcast sound does't come from there. Also it's a pont where a diode is connected to one of the leads on a transistor. I can't find this on the schematic. I can find 3 diodes and none of them connect to a transistor.
:: Where to check next?
::
::Thanks,
::
::Dave
:::Sounds like the caps on rush charge is upsetting the
:::sets -5VDC supply. Your R21 is establishing a referece voltage against the AM AVC line. Therefore, be sure that there are no dried out / intermittent electrolytic caps in that -5 VDCsupply.
:::
:::73's de Edd

Here is a schema thumbnail mark-up with the signal path shown, signal trace from one end to the other
of it on both the FM and the AM path as they co-join at the yellow block and travel on down to the
shared common AF line...the option of which audio is being present, by the bandswitch only selectively
supplying B+ to the appropriate RF frontal circuitry.

http://img338.imageshack.us/img338/2107/bolova1200jewelmovementsr6.jpg

If elect caps are involved ...they are red boxed...probably going to find a connectivity problem
or B+ supply loss in the complete loop shown, however.

Additional board PCB photos are a week away if you specify the components of interest in order to zero in on the exact board, as there are probably 8-10 small sub assembly boards.

Last moment addenda:
I see that you now have added on about X3 but a quick look at the schema must shows X3 diode back to
the IF front of the set...and any audio back there would only be by slope detection....look at the supplied info and you will see that the actual detected audio is via X5 from its IF transformer feed.
Also be sure that C4 10 ufd AVC line electrolytic is bypassing OK.as well as those (3) 100 ufds on
the -5V power supply line.

73's de Edd

Yes, I knew it was odd to be detecting the FM signal way back there. But that's were I find it. It's very weak anywhere else. Maybe the capacitor I'm using for blocking is doing the detecting? It doesn't make any sense to me.

Any, I will do what I usually do with old radios, replace all the paper (none here) and electrolytic (tons here) capacitors. One of them cracked when I was taking it out. I found what looks like fabric inside. Is this paper in them? It was pretty dry. It didn't smell very good either.
It's ok if the other pictures are a week away. The owner of this radio is easy going and not in a rush. No one yet has been able to solve this problem. I want to be the one, well,actually the group, to solve this problem. This radio has such a good tone, it's worth the effort to find the problem. These tiny electrolytc capacitors cost next to nothing. So I might as well, replace them all.

Thanks very much for all your help,

Dave

:Here is a schema thumbnail mark-up with the signal path shown, signal trace from one end to the other
:of it on both the FM and the AM path as they co-join at the yellow block and travel on down to the
:shared common AF line...the option of which audio is being present, by the bandswitch only selectively
:supplying B+ to the appropriate RF frontal circuitry.
:
:http://img338.imageshack.us/img338/2107/bolova1200jewelmovementsr6.jpg
:
:If elect caps are involved ...they are red boxed...probably going to find a connectivity problem
:or B+ supply loss in the complete loop shown, however.
:
:Additional board PCB photos are a week away if you specify the components of interest in order to zero in on the exact board, as there are probably 8-10 small sub assembly boards.
:
:Last moment addenda:
:I see that you now have added on about X3 but a quick look at the schema must shows X3 diode back to
:the IF front of the set...and any audio back there would only be by slope detection....look at the supplied info and you will see that the actual detected audio is via X5 from its IF transformer feed.
:Also be sure that C4 10 ufd AVC line electrolytic is bypassing OK.as well as those (3) 100 ufds on
:the -5V power supply line.
:
:73's de Edd

:Yes, I knew it was odd to be detecting the FM signal way back there. But that's were I find it. It's very weak anywhere else. Maybe the capacitor I'm using for blocking is doing the detecting? It doesn't make any sense to me.
:
:Any, I will do what I usually do with old radios, replace all the paper (none here) and electrolytic (tons here) capacitors. One of them cracked when I was taking it out. I found what looks like fabric inside. Is this paper in them? It was pretty dry. It didn't smell very good either.
: It's ok if the other pictures are a week away. The owner of this radio is easy going and not in a rush. No one yet has been able to solve this problem. I want to be the one, well,actually the group, to solve this problem. This radio has such a good tone, it's worth the effort to find the problem. These tiny electrolytc capacitors cost next to nothing. So I might as well, replace them all.
:
:Thanks very much for all your help,
:
:Dave
:
::Here is a schema thumbnail mark-up with the signal path shown, signal trace from one end to the other
::of it on both the FM and the AM path as they co-join at the yellow block and travel on down to the
::shared common AF line...the option of which audio is being present, by the bandswitch only selectively
::supplying B+ to the appropriate RF frontal circuitry.
::
::http://img338.imageshack.us/img338/2107/bolova1200jewelmovementsr6.jpg
::
::If elect caps are involved ...they are red boxed...probably going to find a connectivity problem
::or B+ supply loss in the complete loop shown, however.
::
::Additional board PCB photos are a week away if you specify the components of interest in order to zero in on the exact board, as there are probably 8-10 small sub assembly boards.
::
::Last moment addenda:
::I see that you now have added on about X3 but a quick look at the schema must shows X3 diode back to
::the IF front of the set...and any audio back there would only be by slope detection....look at the supplied info and you will see that the actual detected audio is via X5 from its IF transformer feed.
::Also be sure that C4 10 ufd AVC line electrolytic is bypassing OK.as well as those (3) 100 ufds on
::the -5V power supply line.
::
::73's de Edd

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dave

Referencing the info below:

http://img338.imageshack.us/img338/2107/bolova1200jewelmovementsr6.jpg
Reviewing:

With your prior comment of using the units AF output stage circuitry for AF signal tracing and assuming that you were connecting into the front end of the
that amp circuitry at about the neg terminal of C12 electrolytic, with a connection to a DC isolative/ coupling cap....right ?

Did you first check in the AM mode and tune into and off of a station and confirm that the TUNING meter is responding, thereby letting us know that the RF circuitry is working all right.

Then go to the FM mode and do the same test to confirm that there is metered response in that mode.

If that is confirmed on both maodes then the next thing would be to select AM and test at the very origin of its signal at

::Yes, I knew it was odd to be detecting the FM signal way back there. But that's were I find it. It's very weak anywhere else. Maybe the capacitor I'm using for blocking is doing the detecting? It doesn't make any sense to me.
::
::Any, I will do what I usually do with old radios, replace all the paper (none here) and electrolytic (tons here) capacitors. One of them cracked when I was taking it out. I found what looks like fabric inside. Is this paper in them? It was pretty dry. It didn't smell very good either.
:: It's ok if the other pictures are a week away. The owner of this radio is easy going and not in a rush. No one yet has been able to solve this problem. I want to be the one, well,actually the group, to solve this problem. This radio has such a good tone, it's worth the effort to find the problem. These tiny electrolytc capacitors cost next to nothing. So I might as well, replace them all.
::
::Thanks very much for all your help,
::
::Dave
::
:::Here is a schema thumbnail mark-up with the signal path shown, signal trace from one end to the other
:::of it on both the FM and the AM path as they co-join at the yellow block and travel on down to the
:::shared common AF line...the option of which audio is being present, by the bandswitch only selectively
:::supplying B+ to the appropriate RF frontal circuitry.
:::
:::http://img338.imageshack.us/img338/2107/bolova1200jewelmovementsr6.jpg
:::
:::If elect caps are involved ...they are red boxed...probably going to find a connectivity problem
:::or B+ supply loss in the complete loop shown, however.
:::
:::Additional board PCB photos are a week away if you specify the components of interest in order to zero in on the exact board, as there are probably 8-10 small sub assembly boards.
:::
:::Last moment addenda:
:::I see that you now have added on about X3 but a quick look at the schema must shows X3 diode back to
:::the IF front of the set...and any audio back there would only be by slope detection....look at the supplied info and you will see that the actual detected audio is via X5 from its IF transformer feed.
:::Also be sure that C4 10 ufd AVC line electrolytic is bypassing OK.as well as those (3) 100 ufds on
:::the -5V power supply line.
:::
:::73's de Edd
:
:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:Dave
:
:Referencing the info below:
:
:http://img338.imageshack.us/img338/2107/bolova1200jewelmovementsr6.jpg
:Reviewing:
:
:With your prior comment of using the units AF output stage circuitry for AF signal tracing and assuming that you were connecting into the front end of the
:that amp circuitry at about the neg terminal of C12 electrolytic, with a connection to a DC isolative/ coupling cap....right ?
:
:Did you first check in the AM mode and tune into and off of a station and confirm that the TUNING meter is responding, thereby letting us know that the RF circuitry is working all right.
:
:Then go to the FM mode and do the same test to confirm that there is metered response in that mode.
:
:If that is confirmed on both modes, then the next thing would be to select AM and test at the very origin of its aidio signal at the cathode of AM det diode X5 and then down that short path until reaching the yellow box reference on the right.

The next test would be to place the unit in the FM mode and test for FM audio origination point at the Ratio det xformers term # 2...then follow down the Fuscia brick road until getting to the base of Q8 FM AF preamp and then check at its collector and then down thru C6 and then you are into the same shared audio buss that the AM co-joins with at the yellow box. As mentioned, the band switch powers up B+ to only the RF circuitry being utilized on that band.

You were commenting earlier about shunting R21 , that
is the AM AVC line (Buss 51) that you would have been affecting.
The line below it(Buss 14) is the AFC corrective feedback voltage to the varactor diode in the tuner.

I have left a line below each query for a response
to use in further more precise analysis.

73's de Edd
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:

:::Yes, I knew it was odd to be detecting the FM signal way back there. But that's were I find it. It's very weak anywhere else. Maybe the capacitor I'm using for blocking is doing the detecting? It doesn't make any sense to me.
:::
:::Any, I will do what I usually do with old radios, replace all the paper (none here) and electrolytic (tons here) capacitors. One of them cracked when I was taking it out. I found what looks like fabric inside. Is this paper in them? It was pretty dry. It didn't smell very good either.
::: It's ok if the other pictures are a week away. The owner of this radio is easy going and not in a rush. No one yet has been able to solve this problem. I want to be the one, well,actually the group, to solve this problem. This radio has such a good tone, it's worth the effort to find the problem. These tiny electrolytc capacitors cost next to nothing. So I might as well, replace them all.
:::
:::Thanks very much for all your help,
:::
:::Dave
:::
::::Here is a schema thumbnail mark-up with the signal path shown, signal trace from one end to the other
::::of it on both the FM and the AM path as they co-join at the yellow block and travel on down to the
::::shared common AF line...the option of which audio is being present, by the bandswitch only selectively
::::supplying B+ to the appropriate RF frontal circuitry.
::::
::::http://img338.imageshack.us/img338/2107/bolova1200jewelmovementsr6.jpg
::::
::::If elect caps are involved ...they are red boxed...probably going to find a connectivity problem
::::or B+ supply loss in the complete loop shown, however.
::::
::::Additional board PCB photos are a week away if you specify the components of interest in order to zero in on the exact board, as there are probably 8-10 small sub assembly boards.
::::
::::Last moment addenda:
::::I see that you now have added on about X3 but a quick look at the schema must shows X3 diode back to
::::the IF front of the set...and any audio back there would only be by slope detection....look at the supplied info and you will see that the actual detected audio is via X5 from its IF transformer feed.
::::Also be sure that C4 10 ufd AVC line electrolytic is bypassing OK.as well as those (3) 100 ufds on
::::the -5V power supply line.
::::
::::73's de Edd
::
::~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
::Dave
::
::Referencing the info below:
::
::http://img338.imageshack.us/img338/2107/bolova1200jewelmovementsr6.jpg
::Reviewing:
::
::With your prior comment of using the units AF output stage circuitry for AF signal tracing and assuming that you were connecting into the front end of the
::that amp circuitry at about the neg terminal of C12 electrolytic, with a connection to a DC isolative/ coupling cap....right ?
::
::Did you first check in the AM mode and tune into and off of a station and confirm that the TUNING meter is responding, thereby letting us know that the RF circuitry is working all right.
::
::Then go to the FM mode and do the same test to confirm that there is metered response in that mode.
::
::If that is confirmed on both modes, then the next thing would be to select AM and test at the very origin of its aidio signal at the cathode of AM det diode X5 and then down that short path until reaching the yellow box reference on the right.
:
:The next test would be to place the unit in the FM mode and test for FM audio origination point at the Ratio det xformers term # 2...then follow down the Fuscia brick road until getting to the base of Q8 FM AF preamp and then check at its collector and then down thru C6 and then you are into the same shared audio buss that the AM co-joins with at the yellow box. As mentioned, the band switch powers up B+ to only the RF circuitry being utilized on that band.
:
:You were commenting earlier about shunting R21 , that
:is the AM AVC line (Buss 51) that you would have been affecting.
:The line below it(Buss 14) is the AFC corrective feedback voltage to the varactor diode in the tuner.
:
:I have left a line below each query for a response
:to use in further more precise analysis.
:
:73's de Edd
:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
::