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Looking for SA-8500II Advice

am trying to figure out the relationship of the protect circuit and amp to see if protect could pull amp output down . but with bias being stable i dont see that it could be that . but why is overload triggering ?
mark the fixer or matt sd might have some insight on this .
 
I was screwing around with it and I sort of accidentally left the amp playing on the right cnachannel at a low level for about a half hour and the right amp board got really hot. The left board stays cool even at higher volumes... Something I that board I think
 
So instead of working I'm thinking about this amp... When I get home, what if I pull the pre-out jumpers out and stick on the in-side another pre-amp (not actually a pre amp, because I don't have one but I'll use my ipod as volume control). Will that essentially treat the SA-8500 II as a power amp and isolate everything? If it sounds good then my problem is outside the power amp and protection circuit?
 
I'd keep it simple at first...

check for bad solder joints, loose or disconnected grounds, etc.

Definitely isolate pre vs power to try and determine the source of the bad sound. if you have another amp with pre in/out features send the signal from the pre of the 8500 to the in of the other amp. Borrow one from a friend if necessary and available.
 
jheu02 said:
I'd keep it simple at first...

check for bad solder joints, loose or disconnected grounds, etc.

Definitely isolate pre vs power to try and determine the source of the bad sound. if you have another amp with pre in/out features send the signal from the pre of the 8500 to the in of the other amp. Borrow one from a friend if necessary and available.
Click to expand...

I will thanks. I've really inspected those board closely and didn't catch anything besides what I pointed out in my first post. Grounds though, I'll check those closer. and isolating the pre amp from the amp, first thing when I get home. well after I put it sort of back together.
 
Okay did the above, used the pre outs like a pre amp and it sounds fine, both channels loud and clear. Used the power amp in and problem is there, right channel sounds low and awful, and relay opens at low volume.
So problem is definitely in the right power amp board.... Right? I'm testing dc voltage again, and I'll double check the bias. It's weird that those two values are so perfect. I'll take any advice
 
Check put this protection relay? It looks different than any one I've seen in any oh her breads.... I.e. Not clear. Think it's been replaced at some point?
 
unplug the amp from the wall then check for shorts at the relay . first you can check at speaker terminals then from pins 17 amp boards to speaker ground .
 
I get about 29k from speaker ground to pin 17, and to the side of the relay power comes in. No continuity to the out side of relay.
 
Same thing on the left side. Question. With amp off, relay open, shouldn't both pins 17 be open? From one another I mean. I get 59k ohm between them
 
no problem there .unless the relay somehow shorts when closed . i cant see how that could happen . i thought this through earlier on .
did you notice what heated up when left on ?
 
The right side will heat up if I play music, quietly mind you. Volume barely up right gets hot, left nice and cool. If I leave balance way over to the left I can play it much louder and right sir stays cool with no sound
 
I have a pretty basic understanding of this and I appreciate your patience with me.... I'm considering trying something tell me if I'm nuts. I'll pull one of those power transistor s out at am time and swap with the known good one on the left side. If I get through all four and he problem stays on the right hen I've ruled out the transistors?
 
am thinking 2 things now .. first check ohms from output transistors tabs to ground . they should be open circuit so long as main caps discharged first . if ok then am thinking power supply issue that would tie in with having to adjust the bias .
check all power supply voltages to see if in spec
 
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