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SA-9100 three feet im in the grave....

djtchort

djtchort

New Member
So, i a few months ago I got an SA-9100. I guess it was being a bad boy, so it was kicked out of the house and left there under a piece of tarp for a year or five. Judging by prehistoric writings on inside the cabinet, it was in for repairs in '82, '94 and whatever year that looks like a cross of a snake and a lightning bolt. Go Chargers! Looks like all of the repairs were done on AWR-032, because i have not detected any more signs of human activity anywhere else. And those signs would be impossible to miss, if those same people left them.

Anyway, the amp got to me with all wires to AWR-032 completely cut off. Thankfully, there was enough wire with insulation so was i was able to re-wrap correct wires in place at the end. The board looked like a burned toast, those big resistors where completely black and cracked. Transistors were the B507D (original, i assume) and RS152, whatever that guy is. The frame... the frame was badly rusted, but only under and around AWR-032.Top and bottom of the frame. Whatever was sprayed on it by those prehistoric people, just ate the frame. Little terminal next to the relay was broken in half and dangling. Had to drill out the relay and the terminal block screw. Had to pull the speaker switch, power switch, headphone plug relay, etc, to be able to sand it and paint it. Rebuilt kit had came in by then, so i did that too. That was my Thanksgiving.

Did the typical re-cap on both power supply boards and protection board. Power it up on DBT, 200w bulb goes full brightness. So i figured i'd go full cowboy and plug it into regular outlet. Immediately blows main 4A fuse. Checked power switch cap, big fat ones and all diodes on AWR-031. Everything checks out... Then, for whatever reason, I pulled 2SC1079 in the left side and the DBT did not light up, power light came on and stayed on. I did a quick test, but did not get any sound. But i am not sure if something was set or plugged wrong on my end. Couple more tests:
1: Swap 2SC1079 - left / right -> right / left -> DBT and power light flash on/off/on/off
2: Leave left 2SC1079 plugged in on the right. left socket empty -> DBT and power light flash on/off/on/off
3: Leave right 2SC1079 plugged in on the left . right socket empty -> DBT and power light flash on/off/on/off
4: Swap 2SC1079 back to how it was - left / left -> right / right -> DBT lights up
5: Leave left 2SC1079 plugged in on the left. right socket empty -> DBT lights up. No power/
5: Leave right 2SC1079 plugged in on the right. left socket empty -> DBT does not light up. Receiver powers up.

This is waaay over my head. Would someone point me in the right direction please and thank you?

TLDR: 9100 can't eve. HALP
 
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Watthour said:
Have ALL the output transistors been pulled and tested out of circuit? If not, it would be a good time to do that.

https://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/
Click to expand...

Not yet. I am waiting on the power amp rebuild kit. I guess will figure this one out soon.

However, I pulled 2SC1079 from SX-838 to try out. According to the page you linked, thank you by the way, the original one is hosed.

Original
B->E 0.000v
B->C 0.000v
E->C 0.000v
E->B 0.000v

Test from 838
B->E 0.524v
B->C 0.516v
E->C OL.
E->B OL.

Seemed like the test one worked fine, because as soon as I turned it on, C8 on AWR-032 popped with smoke and everything, because my dumb ass installed it backwards. Replaced it with an identical spare I had on hand, turned it on. This time DBT light came on.

So, that's where I am at. I have new 2SC679/1079 coming from China, so it's going to be a minute, but the power amp rebuild kit is coming this week, so will see what else I can blow up. This is fun. haha.

Ill update with the results. Thanks again!
 
Ok, you are making a lot of poor choices here, and that needs to stop. You’re making more work for yourself and damaging the amp further.

1. Always use the dim bulb.
2. Pull and test all the outputs.
3. Bad outputs get replaced with MJ21193G and MJ21194G. Not Chinese counterfeits.
4. Always use the dim bulb, until we tell you not to.
 
EastPoint said:
Ok, you are making a lot of poor choices here, and that needs to stop. You’re making more work for yourself and damaging the amp further.

1. Always use the dim bulb.
2. Pull and test all the outputs.
3. Bad outputs get replaced with MJ21193G and MJ21194G. Not Chinese counterfeits.
4. Always use the dim bulb, until we tell you not to.
Click to expand...

Ben, is that you? :)

I don't know if damaging it further is a bad thing here.... I get to learn more. :dunno:

I would gladly get replacement outputs from Mouser, but i'm trying to be a baller on a budget here. $8 per transistor is a little tough for me right now, plus the whole amp cost me about $100 in trades. But in general, I like to keep something on hand. Fake or not, it lets me fix things right away and worry about really fixing it later. I'm just going to use the identical ones from my 838. It won't need them for a while, because its going to be in storage for a while. I'm moving in 3 weeks. But the cap blew up while on DBT
 
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