Looking for a SUNN P.A. eight schematic please.

[antieatingactivist]

Hey everyone. I just had a non working one of these given to me and was wondering if anyone had a schematic or service manual for it. I get a hum from the right channel, but nothing from the left. I'm not really worried about that yet. It appears that the audio signal doesn't make it through the master mixer board. There are a lot of wires in there and I was hoping to have some direction to find where the signal is stopping. I'm pretty sure I can get this thing running with the right info. Thanks in advance.

[loudthud]

I found the schematic for that series called "Generation II". There is a mono and stereo version of the P.A. Eight. I will assume you have the stereo version. The power amp is much like the Coliseum power amp except it only has two power transistors per rail.

It will take me a couple of days to scan. There are quite of few pages.

[antieatingactivist]

Oh wow that would be amazing. I worked on it a bunch today and I've definitely narrowed it down to the Main Mixing Board. (the one with the master sliders). Signal goes in, nothing comes out. I fixed a few broken traces and changed a dead cap out. The loud hum that comes out of the working speaker channel is now gone. It basically sounds like an amp with the volume all the way down now. Just need to get the preamp signal up to the power amp. Anyways, If you don't feel like scanning the whole thing, maybe you could just scan the one for this board, and maybe the power amp if you get a chance. I know I can figure this out. You are a life saver. Thanks!

[loudthud]

There are a number of jacks where the signal passes through when nothing is plugged in. It is common for the contacts in these jacks to go bad, a little contact cleaner usually gets them working again.

One thing to do is bypass the switching jacks with a patch cable.

Try a cable from the "Right (or Left) Master Output" to the "Right Graphic EQ Input" jack.
Try a cable from the "Right Master Output" to the "Power Amp Input" jack.
Try a cable from the "Right Graphic EQ Output to the "Power Amp Input" jack.

[antieatingactivist]

Thanks for the advice, I will give that a try next time I get a chance.

[loudthud]

The originals that I have are B/W photo copies of a color service manual. Some text is hard to read. These are schematics and PCB layouts for the Stereo Preamp board.

[loudthud]

Here are the power supply, the Stereo Master board and the graphic EQ board.

[loudthud]

Finally the power amp and it's PCB layout.

[antieatingactivist]

YOU ARE A CHAMPION!!!!! thanks so much. I actually got it working yesterday. Problem number one. My preamp voltages were +17 and -56. I didn't have a schematic, but this didn't seem right even with my limit knowledge of solid state amplifiers. One of the Transistors on the power supply board was busted. I changed it and now my voltages are +17, and -17. Much better. This must have fried the rc4739 chips. I was able to re-pin an op-amp I had lying around, and it passes sound to the power amp!!! Now I just need to do some cleaning up and I will have an awesome antique PA!!

[loudthud]

Yea, finding a ua723 in the TO-10 package might be tough, but not impossible. There are places you can find on the internet that sell obsolete IC's. The price can be high so shop around. Be advised that there are fakes.

[antieatingactivist]

Luckily that component was fine. It was one of the big mounted TO-2 transistors that was the culprit.