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1976 Trans-AM radio. right channel no stereo light
8/27/2009 11:27:17 PMDave Froehlich
Hello All,
This is the radio I spoke of before. There is no right channel, and no stereo lamp. This radio was working when I shipped it to someone but it was dropped in shipping. I hear the thump from both channels when I measure between the output and the transistor case I get +1.7 volts on one channel and -1.7 volts on the other channel. Also when I measure between the output and the case I get 1.7 volts from one channel and 3 volts on the other. This is kind of odd. The speakers are connected correctly NOT out of phase. One thumps in and the other thumps out. Is this normal. The one that thumps out has no sound. So the problem could be the main amp. But I don't think so. The point of impact was where one of the transformers attaches at the back corner.
There is no model number on the radio anywhere.
Please help. I cannot see or find any problems on any board inside. Where do I look?


Thanks,

Dave

8/28/2009 12:34:53 AMWarren
Hello again Dave.

This radio is on Ebay. Does show the model number on the sticker. If this is like yours, at least you have a model number to go by.

http://cgi.ebay.com/ebaymotors/1970-77-PONTIAC-TRANS-AM-FIREBIRD-AM-FM-RADIO-STEREO_W0QQcmdZViewItemQQ_trksidZp3286Q2ec0Q2em14QQhashZitem483718ae8fQQitemZ310162009743QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

8/28/2009 1:09:05 AMDave Froehlich
Warren,
Yes, that looks like it. It's the model Number: 7313542-1.

Thanks,

Dave
:Hello again Dave.
:
:This radio is on Ebay. Does show the model number on the sticker. If this is like yours, at least you have a model number to go by.
:
:http://cgi.ebay.com/ebaymotors/1970-77-PONTIAC-TRANS-AM-FIREBIRD-AM-FM-RADIO-STEREO_W0QQcmdZViewItemQQ_trksidZp3286Q2ec0Q2em14QQhashZitem483718ae8fQQitemZ310162009743QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
:

8/31/2009 12:48:02 PMEdd





Sir Dave. . . .



How’s about seeing if this data makes a final fulfillment of your need of the schema for that unit.


That’s three full pages of schematic on the RF front end ---the detector stages--- the separate power supply----the audio and
the units FM Multiplex circuitry,


It has now received a reworking into one GEE-IAAAANT unitized schematic.

So big in density that you might have to click onto it to enact a blow up . . . in accordance to your systems internet viewer /browser treatment and software being used..


Sig Tracing Foot prints are additionally added for your audio signal flow path.


I still think since a drop / crash was involved, that the problem still might be a hairline crack across one of the cheeep phenolic P.C.B.,s . . since it certainly isn’t using G-4 quality grade ‘glass materiel !


Also notice the info on the MPX lamp, in case its open, you can test the I.C. lamp driver circuitry by subbing in an ~220 ohm resistor in place of the lamp and then voltage monitoring it for a pull down at the IC pin when the set tuned into a STEEEEEEE-Row station. OR further info has been added onto the schematic, in case you can’t locate a lamp with that low of a current pull.


That’s about it. . . ..


BTW if that was my unit to be troubleshooting , a simplified procedure on the CHEEP ( a. . . la . . . two bent sticks and a rusty rock mode), if you are near a FRY’s, they handle The Philmore brand of crystal earphone . . . . , and by that . . . . I mean that it literally plugs down within your external ear canal cavity . . . , a la 1950's hearing aids.


Take one of those units and install a 2.5 mm mini PHONE JACK into a 35MM aluminum film housing, using that as a shielded and protective PLUG break out adapter and then branch out a test probe and a ground clip on two external leads from that unit.
You then can take that contrivance and walk an audio signals presence /and / enact a quality and gain test from the front detected audio, right on thru to the output coupling capacitors of an AF amp. (That, technique, also being applicable to your current Sansui problem).


IF using on tube equipment with higher voltages, use a GOOD DC isolative blocking capacitor on the
probe lead line . . . . .or else . . . be prepared for an "electrified" ear.






73's de Edd









PONTIAC AM-FM CAR RADIO Info:









9/1/2009 1:01:49 AMDave Froehlich
Edd,
This radio has only two transistors on it. I now notice, and I should know what's going on here, that there is no thump from the right channel. If I let the speaker common float then the right speaker will thump and I will sort of kind of hear the left channel in both speakers. What's going on here? This could be a clue to the problem.
I am beginning to think that it the "usual" output problem.

Thanks very much,


Dave
:
:
:
:
:
:
:
:Sir Dave. . . .
:
:
:
:How’s about seeing if this data makes a final fulfillment of your need of the schema for that unit.
:
:
:That’s three full pages of schematic on the RF front end ---the detector stages--- the separate power supply----the audio and
:the units FM Multiplex circuitry,
:
:
:It has now received a reworking into one GEE-IAAAANT unitized schematic.
:
:So big in density that you might have to click onto it to enact a blow up . . . in accordance to your systems internet viewer /browser treatment and software being used..
:
:
:Sig Tracing Foot prints are additionally added for your audio signal flow path.
:
:
:I still think since a drop / crash was involved, that the problem still might be a hairline crack across one of the cheeep phenolic P.C.B.,s . . since it certainly isn’t using G-4 quality grade ‘glass materiel !
:
:
:Also notice the info on the MPX lamp, in case its open, you can test the I.C. lamp driver circuitry by subbing in an ~220 ohm resistor in place of the lamp and then voltage monitoring it for a pull down at the IC pin when the set tuned into a STEEEEEEE-Row station. OR further info has been added onto the schematic, in case you can’t locate a lamp with that low of a current pull.
:
:
:
:
:That’s about it. . . ..
:
:
:
:
:BTW if that was my unit to be troubleshooting , a simplified procedure on the CHEEP ( a. . . la . . . two bent sticks and a rusty rock mode), if you are near a FRY’s, they handle The Philmore brand of crystal earphone . . . . , and by that . . . . I mean that it literally plugs down within your external ear canal cavity . . . , a la 1950's hearing aids.
:
:
:Take one of those units and install a 2.5 mm mini PHONE JACK into a 35MM aluminum film housing, using that as a shielded and protective PLUG break out adapter and then branch out a test probe and a ground clip on two external leads from that unit.
:You then can take that contrivance and walk an audio signals presence /and / enact a quality and gain test from the front detected audio, right on thru to the output coupling capacitors of an AF amp. (That, technique, also being applicable to your current Sansui problem).
:
:
:IF using on tube equipment with higher voltages, use a GOOD DC isolative blocking capacitor on the
:probe lead line . . . . .or else . . . be prepared for an "electrified" ear.
:
:
:
:
:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:


:
:
:
:
:
:
:
:
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PONTIAC AM-FM CAR RADIO Info:
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9/1/2009 1:06:02 AMDave Froehlich
Edd,
This may not be the model we think it is. It has two DS-515 transistors on a large heat sink on the back. There is no fader control. There is volume, tone and balance. This did work before it had a collision with the inside of its shipping box. From the clues I have given you where should I look?

Thanks,

Dave
:
:
:
:
:
:
:
:Sir Dave. . . .
:
:
:
:How’s about seeing if this data makes a final fulfillment of your need of the schema for that unit.
:
:
:That’s three full pages of schematic on the RF front end ---the detector stages--- the separate power supply----the audio and
:the units FM Multiplex circuitry,
:
:
:It has now received a reworking into one GEE-IAAAANT unitized schematic.
:
:So big in density that you might have to click onto it to enact a blow up . . . in accordance to your systems internet viewer /browser treatment and software being used..
:
:
:Sig Tracing Foot prints are additionally added for your audio signal flow path.
:
:
:I still think since a drop / crash was involved, that the problem still might be a hairline crack across one of the cheeep phenolic P.C.B.,s . . since it certainly isn’t using G-4 quality grade ‘glass materiel !
:
:
:Also notice the info on the MPX lamp, in case its open, you can test the I.C. lamp driver circuitry by subbing in an ~220 ohm resistor in place of the lamp and then voltage monitoring it for a pull down at the IC pin when the set tuned into a STEEEEEEE-Row station. OR further info has been added onto the schematic, in case you can’t locate a lamp with that low of a current pull.
:
:
:
:
:That’s about it. . . ..
:
:
:
:
:BTW if that was my unit to be troubleshooting , a simplified procedure on the CHEEP ( a. . . la . . . two bent sticks and a rusty rock mode), if you are near a FRY’s, they handle The Philmore brand of crystal earphone . . . . , and by that . . . . I mean that it literally plugs down within your external ear canal cavity . . . , a la 1950's hearing aids.
:
:
:Take one of those units and install a 2.5 mm mini PHONE JACK into a 35MM aluminum film housing, using that as a shielded and protective PLUG break out adapter and then branch out a test probe and a ground clip on two external leads from that unit.
:You then can take that contrivance and walk an audio signals presence /and / enact a quality and gain test from the front detected audio, right on thru to the output coupling capacitors of an AF amp. (That, technique, also being applicable to your current Sansui problem).
:
:
:IF using on tube equipment with higher voltages, use a GOOD DC isolative blocking capacitor on the
:probe lead line . . . . .or else . . . be prepared for an "electrified" ear.
:
:
:
:
:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:


:
:
:
:
:
:
:
:
:
:
PONTIAC AM-FM CAR RADIO Info:
:
:
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:
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:

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9/1/2009 2:40:57 PMWarren
Okay David. Another try. This one does have TWO transistors on the back end. Shows tag numbers too.

http://cgi.ebay.com/ebaymotors/1970-77-PONTIAC-TRANS-AM-FIREBIRD-AM-FM-RADIO-STEREO_W0QQcmdZViewItemQQ_trksidZp3286Q2ec0Q2em14QQhashZitem483718ae8fQQitemZ310162009743QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

Hope this is the right one this time.

9/1/2009 3:45:31 PMDave Froehlich
Warren,
Yes, that's it. Now that I figured out where the problem is, I have had this problem before and have solved it. One time it was one of the smaller driver transistors. The output transistor is definitely not turning on. I can make the speaker thump correctly by using a 1.5 volt battery. Why it thumped in reverse is from the other channel, connecting through the common (I don't like to say "ground") speaker connection. I doubt that the output transistor has any problems. I didn't yet remove the "fuse" resistor to check it. In circuit it appears good. I have worked on so many of these I should be able to "solo" at this point. But I always like to discuss it with the group.

DS-515 is the output transistor. There are two DS-515 transistors.
These are the same as ECG or NTE 121. These are not the same as the comon 2N176, but I don't see why one of those wouldn't work because they are very close. I'd try it just as a test. But I'm pretty sure that the output transistor is fine.

Dave
:Okay David. Another try. This one does have TWO transistors on the back end. Shows tag numbers too.
:
:http://cgi.ebay.com/ebaymotors/1970-77-PONTIAC-TRANS-AM-FIREBIRD-AM-FM-RADIO-STEREO_W0QQcmdZViewItemQQ_trksidZp3286Q2ec0Q2em14QQhashZitem483718ae8fQQitemZ310162009743QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
:
:Hope this is the right one this time.
:

9/1/2009 11:49:10 PMDave Froehlich
Edd, Warren,
I found where the wire that powers up the right transistor fell off the board. I reconnected the wire and the other transistor power up but I hear nothing from that channel. When I turn the set on one speaker thumps in (I believe that this is correct). This is the channel that works. The other speaker thumps out, this is the channel that doesn't work. I think it should thump in. I think that this radio has the IC pre-amp, I'll check again. I hope that it's ok. But I'm sure in exists as a generic part. It also has some large "module" looking things in white cases mounted vertically. It's a SIP package whatever it is and there are two of them.

Thanks,

Dave

Thanks,

Dave
:Okay David. Another try. This one does have TWO transistors on the back end. Shows tag numbers too.
:
:http://cgi.ebay.com/ebaymotors/1970-77-PONTIAC-TRANS-AM-FIREBIRD-AM-FM-RADIO-STEREO_W0QQcmdZViewItemQQ_trksidZp3286Q2ec0Q2em14QQhashZitem483718ae8fQQitemZ310162009743QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
:
:Hope this is the right one this time.
:

9/3/2009 10:38:10 AMEdd




Dave . . .DAVE . . . . . DAVE . . . . .



Warren and I . . . . .BUY you books . . . . . SEND you to school . . . . and TEACH you EV-UH-REEE possible thing that WE know,
and yet, you STILL . . . . .





Looks like the first big Chief Pontiac schematic that I sent was far more exotic in its output stage design than the simple "one
lunger" units that you have being being utilized for your units Audio Outputs.


I have lifted clips, involving only the power supply feed, the FM de MPX'er and the AF stage portions from a like vintage
Pontiac so that you can consult that for referencing of the audio flow and the interfacing into its AF output stages.


You did not fill in on the MPX chip used and there are two different ones involved between the two different units, so reference accordingly.


Also, the later unit utilizes a separate STEE-ROW lamp driver . . . .a . . la [AQUA] markup.

HOLD the presses . . . . .I see that you have now come on with a further query about an audio amp / driver " couplate style "
of DM48.

I am now placing a typical circuit use of that DM48 unit , with its voltages , in the [YELLOW BOXED ] area at the very bottom of
the schematic.

If its use in one stage has no signal passage throughput, it must have a "soft" failure mode with no then incurred damage to its
associative output stage and its fuse resistor in the emitter leg.


You should then be able to swap units between channels and then see if the inop stage comes to life, while the then OTHER prior
working channel then goes silent.

Case solved ?, hardest part is then finding a still existant DM48 . . . .no ECG, NTE's, old RCA SK line's subs on this one.



73's de Edd







PONTIAC AM-FM CAR RADIO Thumbnail Schema Info:










9/3/2009 11:01:23 AMDave Froehlich
Edd,
I have sound at the tone control, faint sound at the pre-amp (DM-48) input) and volume control (the 100 ohm resistor makes it the sound faint), but no sound output to the output transistor from the DM-48. I was able to find one, and will try it and let you know if it solves the problem.

Thanks,

Dave
:
:
:
:
:
:
:
:Dave . . .DAVE . . . . . DAVE . . . . .
:
:
:
:Warren and I . . . . .BUY you books . . . . . SEND you to school . . . . and TEACH you EV-UH-REEE possible thing that WE know,
:and yet, you STILL . . . . .
:
:
:
:
:
:Looks like the first big Chief Pontiac schematic that I sent was far more exotic in its output stage design than the simple "one
:lunger" units that you have being being utilized for your units Audio Outputs.
:
:
:I have lifted clips, involving only the power supply feed, the FM de MPX'er and the AF stage portions from a like vintage
:Pontiac so that you can consult that for referencing of the audio flow and the interfacing into its AF output stages.
:
:
:You did not fill in on the MPX chip used and there are two different ones involved between the two different units, so reference accordingly.
:
:
:Also, the later unit utilizes a separate STEE-ROW lamp driver . . . .a . . la [AQUA] markup.
:
:
:
:HOLD the presses . . . . .I see that you have now come on with a further query about an audio amp / driver " couplate style "
:of DM48.
:
:
:
:I am now placing a typical circuit use of that DM48 unit , with its voltages , in the [YELLOW BOXED ] area at the very bottom of
:the schematic.
:
:If its use in one stage has no signal passage throughput, it must have a "soft" failure mode with no then incurred damage to its
:associative output stage and its fuse resistor in the emitter leg.
:
:
:You should then be able to swap units between channels and then see if the inop stage comes to life, while the then OTHER prior
:working channel then goes silent.
:
:
:
:Case solved ?, hardest part is then finding a still existant DM48 . . . .no ECG, NTE's, old RCA SK line's subs on this one.
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:


:
:
:
:
:
:
:

:PONTIAC AM-FM CAR RADIO Thumbnail Schema Info:
:
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:
:
:
:
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:

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9/3/2009 11:09:06 AMDave Froehlich
Edd,
I don't really know what makes the sound so faint when it gets to the input of the pre-amp. Maybe I should remove it (the DM-48) from the circuit and see if the sound where the input pin should be, gets louder. That would indicate some problem inside the DM-48, wouldn't it? Also, can't I make my own "DM-48". As I recall on earlier models, there were a few transistors, I think it was two, and a little circuit between the buffer transistor and the output transistor. These were just general purpose transistors.

Thanks,

Dave
:Edd,
: I have sound at the tone control, faint sound at the pre-amp (DM-48) input) and volume control (the 100 ohm resistor makes it the sound faint), but no sound output to the output transistor from the DM-48. I was able to find one, and will try it and let you know if it solves the problem.
:
:Thanks,
:
:Dave
::
::
::
::
::
::
::
::Dave . . .DAVE . . . . . DAVE . . . . .
::
::
::
::Warren and I . . . . .BUY you books . . . . . SEND you to school . . . . and TEACH you EV-UH-REEE possible thing that WE know,
::and yet, you STILL . . . . .
::
::
::
::
::
::Looks like the first big Chief Pontiac schematic that I sent was far more exotic in its output stage design than the simple "one
::lunger" units that you have being being utilized for your units Audio Outputs.
::
::
::I have lifted clips, involving only the power supply feed, the FM de MPX'er and the AF stage portions from a like vintage
::Pontiac so that you can consult that for referencing of the audio flow and the interfacing into its AF output stages.
::
::
::You did not fill in on the MPX chip used and there are two different ones involved between the two different units, so reference accordingly.
::
::
::Also, the later unit utilizes a separate STEE-ROW lamp driver . . . .a . . la [AQUA] markup.
::
::
::
::HOLD the presses . . . . .I see that you have now come on with a further query about an audio amp / driver " couplate style "
::of DM48.
::
::
::
::I am now placing a typical circuit use of that DM48 unit , with its voltages , in the [YELLOW BOXED ] area at the very bottom of
::the schematic.
::
::If its use in one stage has no signal passage throughput, it must have a "soft" failure mode with no then incurred damage to its
::associative output stage and its fuse resistor in the emitter leg.
::
::
::You should then be able to swap units between channels and then see if the inop stage comes to life, while the then OTHER prior
::working channel then goes silent.
::
::
::
::Case solved ?, hardest part is then finding a still existant DM48 . . . .no ECG, NTE's, old RCA SK line's subs on this one.
::
::
::
::
::
::
::
::73's de Edd
::
::
::
::


::
::
::
::
::
::
::

::PONTIAC AM-FM CAR RADIO Thumbnail Schema Info:
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