Anyone ever re-wired an EOM radio?

Have a 1998 Sunfire that came with the top-of-the-line EOM radio (CD with 7 band EQ and steering wheels controls).  I'd like to add amps to my system, but prferer not to replace this factory head.

Obviously, I could use line level converters to connect the factory level speaker outs to aftermarket amps, but I've heard that the process of changing the amp level to line level degregates signal quality.   So here's my question:

Has anyone here ever opened up a factory radio, found the pre-amp section in it and re-wired the radio so the pre-amp output goes not to the internal factory amp but out to aftermarket amps?  I'm comparatively good with electronics, so if I could get a diagram of the wiring of the GM radio, I could probably do this (even if it involves changing stuff on boards).  I'm just curious to know if anyone else has tried this, and if so, any issues they ran into and in particular where they got wiring diagrams.   Also, I realize that doing this might "mess" up the balance and fade controls onthe factory radio (if they aren't part of the pre-amp section), but I'll cross that bridge when I get to it.

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mikeymars

Hey Mikeymars;

I have seen a guy up here ( not from this area ) that went into this OEM CD player ( 1999 Acura ) and took the signal right from the laser pick up and went fiber optics to the processor. This involved quite the knowledge of internal workings of the CD laser and it's functions ( not for the weak stomach ) and he has a total OEM looking player ( full points in the comp circuit ) and it's also CD quality with no loss in quality straight to the processor.  Here are some pictures from his IASCA Acura EL https://www.damnloud.com/acura/deck.html you can email him if you wish, his name is Wade ( wade@damnloud.com )

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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA

Thanks Jeff, I'll send Wade an email.

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mikeymars

With a little bit of research, it should be able to be done fairly easy. First you need either a pinout of the amp chip, which you should be able to get since these have been used since the mid 80's. Or you need to power up the radio and use an oscilloscope to see which pin is the input, which should be pretty evident. The Radio that you have uses a dual output amp #DM165, there are 2 of them under the heat sink. Remove the amp from the top of the radio, take out the couple of screws and it just plugs in. Remove the top and bottom cover by removing the screws and unsoldering 2 ground straps, then remove the heat sink. You will have to unsolder the amp chips with a soldering iron and a solder sucker. Then just jump a wire on the circuit board where the input to the amp chip used to be to where the output to the connector is. I'm not sure if the input is common ground or floating, the original output was floating output  but it may not become floating until after the amp. This will take a little electronics know how to do, but it should be do-able. I know that if you connect the commons together with the amps still in there you will mess up the balance and fade. I would bet that it won't effect you without the amps in there.

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HotRod

Hot Rod, thank you so much for your very helpful post.  I'll try to look up the chip to see what the pin layout is.

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mikeymars

Mikeymars: anything that I can do to help, just ask...I've been service Delcos for years for an auto recycler. I'm not quite as familliar with this version as the previous one but they use the same output chips. Also I forgot to mention, when you de-solder the amps, dont de-solder the big terminals that protrude through the board near the pins. They are a mounting frame that does not come out with the chip. The chip is held in place by the heatsink screws as well as the solder through the board.

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HotRod