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 Post subject: Need info on Delco car radio - 1988 Olds
PostPosted: May Thu 23, 2019 6:35 pm 
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I'm working on a car radio for a friend and this radio is out of a 1988 Oldsmobile Cutlass Cruiser. The model number is 16065414 but I'm having a devil of a time trying to get information on it, and obtaining a schematic is even more difficult. Problem on it is one channel has nothing but static on it (sounds like frying eggs), and that is even with the volume turned down. No audio comes out of this channel. The other channels do work, but I don't know if the speakers are bad in the car as they didn't sound that great. The wiring harness plugs into the radio in a recess, but the way it's constructed I will have to go to a salvage yard to see if I can get the mating plug as using alligator clips won't work. I might end up soldering wires at the base of the connectors for the wires I need to connect, (I can always unsolder those afterwords). What I'm hoping is that someone will have a schematic of the radio or something very similar so I can troubleshoot this. Mainly I'd like to get the pinout of the output IC's as to what is the speaker, and what are the inputs. I believe there are 4 amplifiers in each IC as it seems to be a BTL output, (the speakers are not grounded). Any help would be appreciated. Here are a couple of pictures of the front and the power/speaker connector and the audio output IC's minus the heatsink they are mounted on.

Thanks
Steve


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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: May Thu 23, 2019 6:50 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Beaver Falls, PA. USA
You may have a bad amplifier chip. Those radios have a bridged output, with the speaker floating between two "hot" leads. Your best bet might be to find a junker radio of the same type, and replace the whole amp board.

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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: May Thu 23, 2019 7:07 pm 
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Joined: Feb Wed 07, 2018 6:52 pm
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Location: Stone Mountain, GA
I used to replace hose chips every day. Ordered them from GM by the box.

A similar board will work but you can get the chips off ebay. Two for less than $20. Will probably be DM98 or DA101. Will be marked on the undersside.

Could be bad caps but most likely chip. As said they are bridged amps, any shorted speaker wires will toast them.

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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: May Thu 23, 2019 8:41 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Shelton, WA
I find with some of these radios from that vintage they develop "cold" solder joints creating all kinds of problems. You can try cleaning it up and soldering around any suspicious areas. Encrusted joints are a dead give away.

billn


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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: May Fri 24, 2019 4:15 am 
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Thanks for the replies, I did find out the IC's are DM165's and the issue in the radio is very common. I need to replace the capacitors on the board, and the right channel chip at the least. First thing is to find out if I can even get them. Maybe one of those high powered external amplifiers is what I need?! I'll stick to keeping it original as the car is in very good "original" condition and the friend wants to keep it that way. I don't now what I would do without the internet! In this car it's the right rear that is static only.

Here's a link of the board in question,

http://www.howtoalmanac.com/Scott/HowTo ... Repair.htm


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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: May Sat 25, 2019 5:57 pm 
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I have a new found respect for people that work on these car radios. I have been able to get the capacitors off the amplifier board and will pull the output IC off later this weekend. I believe what some of the manufacturers do is to put a film of plastic or something like it, and cover the solder side of the board with it. I'm sure it is for protection, but that stuff sure makes it much more difficult to prep for unsoldering components. I'm wondering if I should spray the board when finished to protect it again. I was able to find that IC and hope it's a good one as all of the ones I saw online are "pulls" from old radios. When that's all you have for a choice, that's all you get. The cassette part has issues, but that came out as an assembly which does make it much easier to work on. I'm guessing a belt that has either broken or stretched. I can clean the tape transport while it's out of the radio.


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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: May Sat 25, 2019 11:20 pm 
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Location: 649 Lacy Wilkerson Rd Roxboro, NC 27574
There is a website dedicated to that style of Delco radio that uses the DM 165 chips. I think you can Google DM 165 and it will come up. They describe the total repair and testing procedures and has partial schematics. The leaking capacitors will have eaten some of the circuit traces so all in the vicinity will need to be checked for continuity. All the axial lead caps will need to be replaced as well as several of the little bitty radial one's. Make sure all that need replacing are replaced and all traces fixed before trying your new IC or it will blow it up in short order.

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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: May Sat 25, 2019 11:49 pm 
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I typed "Delco dm165" in Google and the website I was referring to was at the top of the results.

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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: May Sun 26, 2019 12:48 am 
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Location: 649 Lacy Wilkerson Rd Roxboro, NC 27574
I see you already found that website. Sorry.

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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: May Sun 26, 2019 8:06 pm 
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On the circuit board I have, there was just a little bit of the leaky capacitors. The traces are not eaten up at all. What would you recommend to put on the traces to neutralize this acid from the electrolyte out of the capacitors.
Thanks again everybody. Good information.
Steve


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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: May Mon 27, 2019 1:52 am 
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Joined: Apr Thu 11, 2013 11:03 pm
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Location: 649 Lacy Wilkerson Rd Roxboro, NC 27574
I usually have good luck with denatured alcohol and scrubbing it in with a toothbrush. There aren't any components on that board you can hurt with that.

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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: Jun Sun 09, 2019 12:15 am 
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Location: Saint Paul, Minn
Update on the radio.

I replaced every electrolytic cap on the amplifier board and one of the IC's (DM165). Not having any connector to plug the radio in, I soldered pigtails on the back of the connector so I could connect the 4 speakers. I waited for a bench power supply to power it up. I wanted one that had current limiting in case there was a problem. First powered it up with the rear speakers connected and got sound from the cassette player. It needs a belt and cleaning, but it functions. I didn't have any display, so I went looking further. I find out the one connector I wasn't sure about had 2 connections, and one of them was the +12 volts always on. Once it had power, the display worked. Now it's being tested with 4 speakers and everything is working well. Next week I will be going to get the belt and can consider it finished. I did replace all of the bi polar caps with ceramic ones. They had a much higher temperature range and won't eventually leak. While this was more of a challenge to work on because of the lack of documentation and the way it's constructed, I'm happy with the repair. You guys that do this for a living certainly have my respect.

Steve


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 Post subject: Re: Need info on Delco car radio - 1988 Olds
PostPosted: Jun Sun 09, 2019 12:23 am 
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Joined: Feb Wed 07, 2018 6:52 pm
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Location: Stone Mountain, GA
Good to hear it is working.

For those that don't have a current limited supply, a car brake light bulb in series with the supply will work. The radio will become unstable if you turn up the volume buy it will protect from shorts.

I used to use it also for shorted radios. I could use a DMM to measure voltages and see small drops in wires and circuit traces to see where the short was.

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