Car Audio Delco identification and restoration / repair

[toty79]

Hello to all friends and welcome back
I am struggling with a complete restoration of a Delco GM car radio, I have already taken these car radios in the past but this is a bit more complicated and has many problems, in the meantime I ask if anyone knows the exact model in order to trace a possible repair scheme, I have if someone and they have it I would be very happy, I am attaching photos and I also ask what is the purpose of that two-wire connector that comes out from the back (orange-brown) the radio turns on with the display completely off, the mechanics make strange and non-strange noises accepts the tape, the audio is distorted on all channels, first of all I would like to start with the display off, I have only redone some soldering but nothing has changed, I have also found two faulty micro-lamps have been changed and now they turn on but the display always remains off, is it possible that it has something to do with the small connector on the back?
thank you all

[keeney123]

Re: Car Audio Delco identification and restoration / repair

Seems to be a model number 16066335.

This site may help.

https://classicoldsmobile.com/forums...-1990s-150403/

[redwire]

Re: Car Audio Delco identification and restoration / repair

I found some info here https://pcbisolation.com/blog/repair...s-delco-radio/

[R_J]

Re: Car Audio Delco identification and restoration / repair

I believe the 2 pin plug is for constant +12v (memory) and display lamp (controlled by dash lamp dimmer)

[toty79]

Re: Car Audio Delco identification and restoration / repair

Thanks a lot R_J
I just connected the red to the + 12v but I still have a display turned off, what should I connect to the brown cable?
obviously I feed everything on the counter

[R_J]

Re: Car Audio Delco identification and restoration / repair

The Red wire is likely for the constant memory backup, the brown should be for the display, connecting it to +12v should light the display

[toty79]

Re: Car Audio Delco identification and restoration / repair

Just tried + 12v on the brown cable too but I still get display off, troubleshooting tips?

[R_J]

Re: Car Audio Delco identification and restoration / repair

See if this is close.

[keeney123]

Re: Car Audio Delco identification and restoration / repair

See if this is close.

Thanks RJ for helping out. I believe he will be able to use this schematic for the display troubleshooting. He just needs to remember his wrist strap to ground when working on it. At per instructions on page 26.

[toty79]

Re: Car Audio Delco identification and restoration / repair

R_J thanks you are fantastic
Keeney123 you are absolutely right and almost identical and you will give me a lot of help, the only question at the moment looking at the schematic and how to identify the IC and transistors as they have a dedicated Delco code and also in the parts list sheet they are marked with a code that does not carry to nothing as equivalence I maybe have the datasheet of the component to be tested, for the moment I thank you all and I will keep you updated

[keeney123]

Re: Car Audio Delco identification and restoration / repair

I believe the DM on the chip may stand for Delco Motorola. This could be wrong. It just would make sense to have an IC manufacturer build your ICs with your design and then put the product together with your name on it.

Some sites list the DM as Delco Modules. Would be interesting to investigate further.

The DM Delco IC are available on Ebay.

Another place to buy https://www.ceitron.com/semi/ceidelco.html

Just when buying from above people be cautious.

Delco is going to want you to buy their product that is why no listing. I guess when troubleshoot one would have to look at the schematic and figure out what to expect. Without the actual datasheets there will be a little guess work to figure a working part.

I believe Delco Remy is now just Remy. One could try and contact them for the data sheets as these parts are 32 years old, they just may give you them.

Go Marconi!

[redwire]

Re: Car Audio Delco identification and restoration / repair

The two-pin connector P201, schematic shows one wire is BATT, other is Park Lights. So the unit will not power up unless you have power to BATT (as well as IGN and RCVR).
The 12-pin connector also has park lights (DIM), IGN 14V, RCVR 14V (power amps) but can give no 5V power, that seems to come separately from the 2-pin connector. Very strange Delco. Maybe they wanted a quiet take off point.
On the 2-pin connector, you can put power there, not sure if orange or brown wire.
With these, NEVER connect/short a loudspeaker output to ground or you will blow the power amp IC's.

[R_J]

Re: Car Audio Delco identification and restoration / repair

The 2 pin cable will require +12 volts for the Batt lead as well as +12 volts to the PK Lights lead. This controls the display. the DIM connection controls the brightness of the internal (trim panel) lamps and may also control the brightness of the led display as well, so the dim also need +12 volts (or less for a dimmer display)

[toty79]

Re: Car Audio Delco identification and restoration / repair

Update
Thanks to the diagram I have identified R240 from 6.8 ohm (page 23 and 27) which incredibly measured 30k, replaced and now we have a clock display on (attached photo) but as you can still see the small am / fm display is off, so something is still not go, all your help is very precious and I am grateful to you

[keeney123]

Re: Car Audio Delco identification and restoration / repair

Update
Thanks to the diagram I have identified R240 from 6.8 ohm (page 23 and 27) which incredibly measured 30k, replaced and now we have a clock display on (attached photo) but as you can still see the small am / fm display is off, so something is still not go, all your help is very precious and I am grateful to you

Glad to hear that you got some of the display working. Hopefully you will find the solution to the small display.

[R_J]

Re: Car Audio Delco identification and restoration / repair

If the clock display is on, it could be the radio in not actually turned on. What is the voltage on the resistor R240? if it was open, something else on that line may be damaged, check if you have +5v on U204

[toty79]

Re: Car Audio Delco identification and restoration / repair

Hi guys ... the + 5v on U204 were present but with pulsating voltage due to a short on C231 electrolytic 16v 100uf replaced and now we also have the second display on, now that I have both displays I am dedicating myself to the amplification part, the whose audio is almost a hiss on all channels, the volume responds to the control, four IC DM113 are mounted on the amplification circuit we hope they are not fried

[keeney123]

Re: Car Audio Delco identification and restoration / repair

Hi guys ... the + 5v on U204 were present but with pulsating voltage due to a short on C231 electrolytic 16v 100uf replaced and now we also have the second display on, now that I have both displays I am dedicating myself to the amplification part, the whose audio is almost a hiss on all channels, the volume responds to the control, four IC DM113 are mounted on the amplification circuit we hope they are not fried

You are tenacious a good trait in an electronic technician.

[toty79]

Re: Car Audio Delco identification and restoration / repair

Thanks keeney123 you do what you can

Changed all electrolytic capacitors on the amplifier board but still I get the same hiss, by applying an external source on connector J301 (page 7) all four channels sound perfectly, so it is excluded that it is the amplifier, but instead the noise comes from the preamplified part, the thing gets complicated and I can't understand what kind of component could affect all four channels, I would also exclude capacitors on the preampl section ... but now I find myself in a deadlock ... all the advice is well accepted ... thank you

[keeney123]

Re: Car Audio Delco identification and restoration / repair

Thanks keeney123 you do what you can

Changed all electrolytic capacitors on the amplifier board but still I get the same hiss, by applying an external source on connector J301 (page 7) all four channels sound perfectly, so it is excluded that it is the amplifier, but instead the noise comes from the preamplified part, the thing gets complicated and I can't understand what kind of component could affect all four channels, I would also exclude capacitors on the preampl section ... but now I find myself in a deadlock ... all the advice is well accepted ... thank you

Perhaps R_J can help you with that when he gets a chance.