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please help with a "new" Sansui AU-9900

Guys that's not dc, the pops I mean. It's probably some old transistors in the preamp . Not in the power amp 90%.
Apart from some dc that is obviously present and triggers the protection circuit.
sheiku , your amp is in need of some serious service. Where do you live ? Romania?
 
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Yes north east of Romania.
But I do not have any company or specialist in my city to repair my amplifiers. There is one company but I avoid it because of some problems in the past with them.
For about 3 days in my spare time ( I have also some litle childrens near me :) ) I tried to measure some components in the PCB , to study some basic electronics books and tutorials. I try to understand the skematic if 9900 ( but the pdf scan is very bad).
It is a very slow process but I have no other alternative, excepting study and trials..hope to succeed. I will post some results here as I will have some.
PS I also waiting for a desolderig station with pump to remove some transistors to test them outside. The only way to test transistors is outside the pcb/ circuit ?
Thank you all.
 
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One of the problems with the AU-9900 is that there are a lot of passthrough connections on the boards, and cold solder joints need to be checked for. By passthrough connections, there are some signals that leave one board, through another, to reach the third. This adds to the complexity, unfortunately. If I were you, I would start with reflowing the solder connections, replacing the relay, all electrolytic caps, and as well, search here in AK for AU-9900 restore threads. I'm pretty certain there are.
 
Hello, I came with updates and strange news..
I received yesterday an new soldering station and some electronic tools and i said to myself to reopen the 9900. To follow your advice to search some problems inside.
I saw the board F-2567 with some interventions on it and some soldering tentative. I will post tommorow some pictures because i do not like its condition..But the subject of this post it is not this board..
I found an board near the front panel quite oily on all surface. i used some paper to clear the thin oil. The oil surface was from deoxit..( or the deoxit substitute i used- in my country i do not have deoxit)
After that i closed the amp and i tested..and surprise, the amp is working. So no those scary pops. no loud pops at all.Just the hiss in the right speaker is present.
So what could be happened? A sort of temporary short circuit from the excessive deoxit procedure? I know that the deoxit is not conductive even on PCB , but maybe my cleaner was not as good as chemical composition as the original deoxit.
I will post some pictures with the composition of my cleaner and also with the PCB boards i found with some past interventions.

Regards
 
and after 2 days ..it stats again to pop..not too loud, sometimes there are pops..
It is like cat and mouse.
I think i will buy an oscilloscope.
 
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