I'm searching for the schematics of a Cadillac (Delco) autoradio type: 7274905.
It seems that the ouput stage is not working properly, for the output is getting disturbed when the volume is put up.
It is a tube radio with one transistor DS-501
Can anyone help me?
Thanks,
Piet
Try these links Piet.
Bill
http://img.villagephotos.com/p/2004-12/912127/7274905pg1.jpg
http://img.villagephotos.com/p/2004-12/912127/7274905pg2.jpg
http://img.villagephotos.com/p/2004-12/912127/7274905pg3.jpg
Wellll, it looks like the submitted schematic references of SAMS 499#5 has a negative resolution characteristic.
It seems like back in the ‘60’s I had used a Caddie “ Wonder Bar” radio and along with antenna and battery being built into a plywood box. This gave me a portable unit which provided me yeoman service in the sparse station environs of the Mojave. I know that my volume was VERY adequate, so I suspicion that your unit is only producing but limited output before the sound distorts and splatters.
My money is on the opening/drying out of the two electrolytics in the unit that are in the internal cavity just back from the heat sink that the ‘501 is mounted on. The alum canned unit is a three section unit of 750 uf @ 16 Vdc - 350ufd @ 16 Vdc- 750 ufd @ 16 Vdc and 4 ufd @ 11.5 Vdc.
Since you can’t resolute the schematic, the connections are thus:
1. Locate the collector lead of the ‘501 and find that there is a 4 ufd @ 11.5 Vdc section of the alum electrolytic connected with its positive terminal.
2. The radio’s main switched DC 12 VDC power passes thru a (R30) 56 ohm to one 750 ufd cap section of the alum can unit .
3. Find the emitter of the ‘501 and you will find it going to a .47 ohm emitter resistor, on the other side of that resistor, find the second 750 ufd @ 16 Vdc section of that can connected and bypassing that juncture to ground.
4. Also, back on the emitter connection of the‘501 , there was also a positive lead of a 1000 ufd 1 VDC single section cardboard encased capacitor. That cap has its negative lead connected to the black lead of the ‘501 base driver transformer. If it needs replacement ....live it up and use a 5/6/10 or 16 VDC rated unit.
5. The last section of the canned electrolytic is its 350 Ufd @ 16 Vdc and that is connected to the screen grid ( Pin 3) of the low plate potential 12DV8 audio driver tube.Very critical for bypassing of that type of tube in order to provide adequate base drive to the output stage.
Lastly there is a R3 175 ohm ( 80 ohm stop) bias pot located between the canned electrolytic and the chassis rear, riveted to it. In a physical variable wirewound "buzzpot" type of control.
In case that control has been "diddled" , to properly reset the bias value, lift the wire from the collector of the '501's collector and insert a series DC milliameter and trim in the collector current consumption to 1 amp with adjustment of R3.
73's de Edd
*************************************************************************************************************
:Hello,
:
:I'm searching for the schematics of a Cadillac (Delco) autoradio type: 7274905.
:It seems that the ouput stage is not working properly, for the output is getting disturbed when the volume is put up.
:It is a tube radio with one transistor DS-501
:Can anyone help me?
:
:Thanks,
:
:Piet
Bill
:
:*************************************************************************************************************
:
:Wellll, it looks like the submitted schematic references of SAMS 499#5 has a negative resolution characteristic.
:
:It seems like back in the ‘60’s I had used a Caddie “ Wonder Bar” radio and along with antenna and battery being built into a plywood box. This gave me a portable unit which provided me yeoman service in the sparse station environs of the Mojave. I know that my volume was VERY adequate, so I suspicion that your unit is only producing but limited output before the sound distorts and splatters.
:
:My money is on the opening/drying out of the two electrolytics in the unit that are in the internal cavity just back from the heat sink that the ‘501 is mounted on. The alum canned unit is a three section unit of 750 uf @ 16 Vdc - 350ufd @ 16 Vdc- 750 ufd @ 16 Vdc and 4 ufd @ 11.5 Vdc.
:
:Since you can’t resolute the schematic, the connections are thus:
:
: 1. Locate the collector lead of the ‘501 and find that there is a 4 ufd @ 11.5 Vdc section of the alum electrolytic connected with its positive terminal.
:
: 2. The radio’s main switched DC 12 VDC power passes thru a (R30) 56 ohm to one 750 ufd cap section of the alum can unit .
:
:3. Find the emitter of the ‘501 and you will find it going to a .47 ohm emitter resistor, on the other side of that resistor, find the second 750 ufd @ 16 Vdc section of that can connected and bypassing that juncture to ground.
:
: 4. Also, back on the emitter connection of the‘501 , there was also a positive lead of a 1000 ufd 1 VDC single section cardboard encased capacitor. That cap has its negative lead connected to the black lead of the ‘501 base driver transformer. If it needs replacement ....live it up and use a 5/6/10 or 16 VDC rated unit.
:
: 5. The last section of the canned electrolytic is its 350 Ufd @ 16 Vdc and that is connected to the screen grid ( Pin 3) of the low plate potential 12DV8 audio driver tube.Very critical for bypassing of that type of tube in order to provide adequate base drive to the output stage.
:
:Lastly there is a R3 175 ohm ( 80 ohm stop) bias pot located between the canned electrolytic and the chassis rear, riveted to it. In a physical variable wirewound "buzzpot" type of control.
:
:In case that control has been "diddled" , to properly reset the bias value, lift the wire from the collector of the '501's collector and insert a series DC milliameter and trim in the collector current consumption to 1 amp with adjustment of R3.
:
:73's de Edd
:
:*************************************************************************************************************
:
:
::Hello,
::
::I'm searching for the schematics of a Cadillac (Delco) autoradio type: 7274905.
::It seems that the ouput stage is not working properly, for the output is getting disturbed when the volume is put up.
::It is a tube radio with one transistor DS-501
::Can anyone help me?
::
::Thanks,
::
::Piet
Sorry for my late reply but I was a few days on a trip. Bill the schematics via email are perfect and with the tips from Ed it must be possible for me to solve the problem. This week I will start working on it and I let you know what happens.
So thanks for the support!
Piet
:I sent Piet the schematic by email. Kept original size. No problem with these. Tried to make schematic available in case others can use but host site for links makes changes.
:
:Bill
:
::
::*************************************************************************************************************
::
::Wellll, it looks like the submitted schematic references of SAMS 499#5 has a negative resolution characteristic.
::
::It seems like back in the ‘60’s I had used a Caddie “ Wonder Bar” radio and along with antenna and battery being built into a plywood box. This gave me a portable unit which provided me yeoman service in the sparse station environs of the Mojave. I know that my volume was VERY adequate, so I suspicion that your unit is only producing but limited output before the sound distorts and splatters.
::
::My money is on the opening/drying out of the two electrolytics in the unit that are in the internal cavity just back from the heat sink that the ‘501 is mounted on. The alum canned unit is a three section unit of 750 uf @ 16 Vdc - 350ufd @ 16 Vdc- 750 ufd @ 16 Vdc and 4 ufd @ 11.5 Vdc.
::
::Since you can’t resolute the schematic, the connections are thus:
::
:: 1. Locate the collector lead of the ‘501 and find that there is a 4 ufd @ 11.5 Vdc section of the alum electrolytic connected with its positive terminal.
::
:: 2. The radio’s main switched DC 12 VDC power passes thru a (R30) 56 ohm to one 750 ufd cap section of the alum can unit .
::
::3. Find the emitter of the ‘501 and you will find it going to a .47 ohm emitter resistor, on the other side of that resistor, find the second 750 ufd @ 16 Vdc section of that can connected and bypassing that juncture to ground.
::
:: 4. Also, back on the emitter connection of the‘501 , there was also a positive lead of a 1000 ufd 1 VDC single section cardboard encased capacitor. That cap has its negative lead connected to the black lead of the ‘501 base driver transformer. If it needs replacement ....live it up and use a 5/6/10 or 16 VDC rated unit.
::
:: 5. The last section of the canned electrolytic is its 350 Ufd @ 16 Vdc and that is connected to the screen grid ( Pin 3) of the low plate potential 12DV8 audio driver tube.Very critical for bypassing of that type of tube in order to provide adequate base drive to the output stage.
::
::Lastly there is a R3 175 ohm ( 80 ohm stop) bias pot located between the canned electrolytic and the chassis rear, riveted to it. In a physical variable wirewound "buzzpot" type of control.
::
::In case that control has been "diddled" , to properly reset the bias value, lift the wire from the collector of the '501's collector and insert a series DC milliameter and trim in the collector current consumption to 1 amp with adjustment of R3.
::
::73's de Edd
::
::*************************************************************************************************************
::
::
:::Hello,
:::
:::I'm searching for the schematics of a Cadillac (Delco) autoradio type: 7274905.
:::It seems that the ouput stage is not working properly, for the output is getting disturbed when the volume is put up.
:::It is a tube radio with one transistor DS-501
:::Can anyone help me?
:::
:::Thanks,
:::
:::Piet
Thanks to you and the schematics I succeeded inrepairing the radio.
Two things were defect:
The Elco (C2) 1000uF . This didn't solve the problem!
and the major problem:
The potmeter (R3) for setting the bias current of the output transistor was defect. This is a wirewound potmeter and it was broken. I set the output current with a fixed resistor and now the radio works well.
Piet
:*************************************************************************************************************
:
:Wellll, it looks like the submitted schematic references of SAMS 499#5 has a negative resolution characteristic.
:
:It seems like back in the ‘60’s I had used a Caddie “ Wonder Bar” radio and along with antenna and battery being built into a plywood box. This gave me a portable unit which provided me yeoman service in the sparse station environs of the Mojave. I know that my volume was VERY adequate, so I suspicion that your unit is only producing but limited output before the sound distorts and splatters.
:
:My money is on the opening/drying out of the two electrolytics in the unit that are in the internal cavity just back from the heat sink that the ‘501 is mounted on. The alum canned unit is a three section unit of 750 uf @ 16 Vdc - 350ufd @ 16 Vdc- 750 ufd @ 16 Vdc and 4 ufd @ 11.5 Vdc.
:
:Since you can’t resolute the schematic, the connections are thus:
:
: 1. Locate the collector lead of the ‘501 and find that there is a 4 ufd @ 11.5 Vdc section of the alum electrolytic connected with its positive terminal.
:
: 2. The radio’s main switched DC 12 VDC power passes thru a (R30) 56 ohm to one 750 ufd cap section of the alum can unit .
:
:3. Find the emitter of the ‘501 and you will find it going to a .47 ohm emitter resistor, on the other side of that resistor, find the second 750 ufd @ 16 Vdc section of that can connected and bypassing that juncture to ground.
:
: 4. Also, back on the emitter connection of the‘501 , there was also a positive lead of a 1000 ufd 1 VDC single section cardboard encased capacitor. That cap has its negative lead connected to the black lead of the ‘501 base driver transformer. If it needs replacement ....live it up and use a 5/6/10 or 16 VDC rated unit.
:
: 5. The last section of the canned electrolytic is its 350 Ufd @ 16 Vdc and that is connected to the screen grid ( Pin 3) of the low plate potential 12DV8 audio driver tube.Very critical for bypassing of that type of tube in order to provide adequate base drive to the output stage.
:
:Lastly there is a R3 175 ohm ( 80 ohm stop) bias pot located between the canned electrolytic and the chassis rear, riveted to it. In a physical variable wirewound "buzzpot" type of control.
:
:In case that control has been "diddled" , to properly reset the bias value, lift the wire from the collector of the '501's collector and insert a series DC milliameter and trim in the collector current consumption to 1 amp with adjustment of R3.
:
:73's de Edd
:
:*************************************************************************************************************
:
:
::Hello,
::
::I'm searching for the schematics of a Cadillac (Delco) autoradio type: 7274905.
::It seems that the ouput stage is not working properly, for the output is getting disturbed when the volume is put up.
::It is a tube radio with one transistor DS-501
::Can anyone help me?
::
::Thanks,
::
::Piet