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Sansui 8080DB... again ;-)

SJoannette

SJoannette

New Member
Hi to everyone

I'm trying to make a 8080DB working again. Let me explain the problem. When I open it, the DC voltage on each channels are about 0 mv and they increase until it goes over 1.5 volt and the protection mode start. I recap the driver board and the power board. Also change the two fuse resistors on the driver board. Everything else seem to be ok. Do you have an idea of what's going on? It's surely something that heat up but witch one? Already check all the output transistors and they are all goods. Even if I remove all the transistors, the problem remains.
 

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I am assuming the receiver is out of protection without the driver board installed. In that case, first, you should replace all of the fuse resistors in the main amp and then start troubleshooting.
 
There are 14 fuse resistors on that driver board. Which two did you change? R33/34 are the most troublesome but don't overlook the others. They are listed in the service manual.

- Pete
 
ahhh, yes it goes out of protection mode after removing the driver board and I replace R33 et 34 only. I will replace all the others. Thanks.
 
Finally change all the fuse resistors on the driver board and the power board. Always the same thing. Here's a video of the problem. Anyone have an idea? Can it be the main capacitors?

 
What I'm sure right now. The problem doesn't came from the driver board. The reason, if I remove the driver board, the LED goes green. But if I put back immediately the driver board, the LED stay red. I have to let it cooled down before powering up again. So it's something somewhere else that freak out when he's heated up. Also, the DC voltage raise his exactly the same thing on each channels.
 
Have you checked or replaced the diodes D01-D04? Have you replaced D05-D06 VD1212 varistors?
 
SJoannette said:
What I'm sure right now. The problem doesn't came from the driver board. The reason, if I remove the driver board, the LED goes green. But if I put back immediately the driver board, the LED stay red. I have to let it cooled down before powering up again. So it's something somewhere else that freak out when he's heated up. Also, the DC voltage raise his exactly the same thing on each channels.
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This makes no sense. If it comes out of protection with the board, the board is the problem.
I'm assuming you checked all emitter resistors?
 
ivandezande said:
Do this. Nothing you say about this unit is relevant until then.

View attachment 2054476

There are also two 4.7 ohm fusables on the protection board, and three 1 ohms on the power supply. They alllll have to go.
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Hi. Finally goes back on my 8080DB. I rebuilt everything on the driver board, include all the transistors. I also replace the two fuse resistor on the relay board, and when I came on the power board to replace the three 1 ohm fuse resistors, there is is ther fuse instead of resistor on the board??? Is this an error in the service manual or what?

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