Sc-811 Amp/fader / preamp Problems

timd · Post by **timd** » 19 Apr 2011, 10:41

First off, wow what a great website. Sooo much useful information here!!! Onto my issues...

I've got a SC-811 in my '95 wagon, and have run into a couple problems I'm hoping I can get some insight into.

1) The front speakers intermittently work. When the start or stop working the sound fades in/out, it's not suddenly on/off. I've disassembled the entire HU, cleaned each and every circuit board, connection, switch, etc. No difference. I read that this may be due to an issue with the internal amp, which I can see as being a possible problem, but...

2) I'm installing a bunch of left over stereo equipment from other cars I've had, and in wanting to keep with a stealth install am looking to keep the stock HU, so I made myself a pre-amp cable. But, a problem:
2a) There is no voltage coming across any of the speaker channels (FL, FR, RL, RR). Remote On has full +12v and signal ground has radio chassis continuity. What gives? Going off info from this thread:
https://www.matthewsvolvosite.com/forums ... =1&t=30204

3) So... how does the radio decide what to power? I'd absolutely love to not go hunting for another HU, I'd rather fix what I've got. IF the fader also controlled pre-amp, then I could see the fronts not getting any signal, but the rears don't either.

Oh, and one more thing not directly related to Pre-amp -

The trunk mounted 6disc cd changer is STOOOPID slow to load a cd, switch cd, change track, resume from pause, everything. it's literally faster to go to the local hardware store, buy a hammer, and hit myself in the foot.

I haven't taken the changer apart to see if a good cleaning would help, are there any other suggestions? I just came across this:
https://www.matthewsvolvosite.com/forums ... 34&start=0
Will try that this afternoon to see if it helps at all.

Post by **JRL** » 19 Apr 2011, 10:56

Why not?
You should be able to find a good 815-816 CD and Cassette for anywhere from 40 to 60 bucks with a 5 minute install
Why waste your time with this old one.
(I had a perfect 813 I just sold for 20 bucks, better than your 811)
If for some reason your amp is bad, (VERY rare) those too are VERY cheap used, no one needs one and there are tons around and available

timd · Post by **timd** » 19 Apr 2011, 11:03

Thanks for the input, but I just like fixing stuff

If I have to I'll get a used HU, but like I said i'd rather repair this one if possible

Post by **JRL** » 19 Apr 2011, 16:29

There's always one in a crowd, knock yourself out

pwnyoda · Post by **pwnyoda** » 07 Apr 2018, 09:58

You could probably replace the 2 main transistors on the amp board. I noticed on my radio one of the pins, on each transistor, looks sightly burnt and the heat sync paste looked dry when I separated the aluminum back from the circuit board.