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Issue with SA-7800

its where the large capacitors are and the fuses .
you dont get into the protect circuit . it has to be diagnosed by checking voltages
 
Saw this on pg 10 of the service manual... would any of this apply to my current situation?

pg10_servicemanual.jpg
 
I'm just lost. This is so frustrating. So I believe this is the underside of the power supply board. It all looks mostly the same to me? I mean, am I supposed to spot something in particular that would signify it needs to be re-soldered?

20180801_202655.jpg


20180801_202642.jpg
 
Where are these transistors that you're talking about on the little heat sinks? I mean, do they have a corresponding number?
 
Here is the top of the amp board where the large capacitors are and the fuses. So what transistors am I look for here? Can you point them out?
20180801_203245.jpg
 
That is PS board. Protection circuit is on amp board, in the middle, I see the relay in black housing made by DEC.
 
While you are in there, you may want to pull and check continuity and clean the fuses. Also make sure they are snug in the sockets.
 
I may just Reflow q34 and Q35 because you are right it does look like those have been soldiered and it from other pictures of dry joints it looks like that may be a dry joint as well.

Question on the power lamp indicator that I need to replace do I need that specific lamp or can I replace that with a different one does the replacement need to have a certain voltage with it?

I was thinking of even trying to find a replacement on eBay and soldiering the wires to the old one but didn't know if there were other options
 
Check the voltage on pilot lamp at pins no 37 and 60 first. You must have 7.2V AC (alternative current)
 
As Pete said check all fuses, then voltages on Q34 and Q35 collectors. You should have +63V and -63V. Check voltages at pin 29 ( 46V) and 32 (-46V)
 
Jumping in late here, and I don't mean to divert troubleshooting; however, I would point the OP to this thread. This was my first post on AK nearly 4 years ago and I was lucky enough to get the immediate attention of Mark The Fixer. The issues that I had were not on the main board, but on the "phono board" that is mounted upside down near the right front panel. In my case, the amp was failing to come out of protection on a cold start but would respond after warming up. It did turn out to be cold solder joints on that board.

Hope this helps!
 
buffdriver said:
Jumping in late here, and I don't mean to divert troubleshooting; however, I would point the OP to this thread. This was my first post on AK nearly 4 years ago and I was lucky enough to get the immediate attention of Mark The Fixer. The issues that I had were not on the main board, but on the "phono board" that is mounted upside down near the right front panel. In my case, the amp was failing to come out of protection on a cold start but would respond after warming up. It did turn out to be cold solder joints on that board.

Hope this helps!
Click to expand...
Buff thanks so much for jumping in! Actually I quoted your thread in my original post and the reason I decided to even make my own Post in the hopes that I could get mine fixed too. Pete and some others have been a great help so far!

I will take all the help I can get because I am a complete Noob here that doesn't even completely know how to measure voltage yet. I think im doing it right though now
 
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