Sansui AU-9900 Main-In Inoperable

Zekeman

Zekeman

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I have a fully restored (several years back) Sansui AU-9900 that works perfectly (in fact both Echowars and MarktheFixer have touched it) except for the "main-in" section to use as a power amp. The "Pre-out" works properly.

I am testing for continuity from the RCA's to the driver board and it is OK. I notice that some of the diodes are the old DS430, VD1212, and 1S953 styles and I can replace those.

Aside from that...Any insight as to where the issue may be?

Thanks!
 
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So are you saying that everything is ok when jumpers are in from pre-out to main in?

If so there shouldn't be a problem with the amp section since it works fine.

I'd check the pre out on the other pre amp.
 
To rephrase the question, does it work properly as an integrated amp, using it's own preamp and power amp?
 
It works perfectly as an integrated.

The "pre-out" works perfectly.

There are no jumpers on this model. It has a "connected/separated" switch.
 
Don't think so. I used my AU-717 for a pre. I also used the 717 as a pre for another amp and it works fine.
 
So you have continuity between the 'Main In' RCA jacks and points 01 & 04 on the driver boards with the connected/separated switch set to separated ?

But it does not produce sound when you connect either its own pre-amp (via RCA jumper cables from 'Pre-Out' to 'Main in') or another Pre-Amp to the 'Main In' RCA jacks ?

PS: Bolded text, I KNOW these cables are not really needed - but just want to duplicate the conditions using its own pre-amp).
 
I pulled the driver board last night and looked at the schematic and saw the VD1212 diodes so I decided to replace them. While it was apart I also touched up the solder joints on the driver. I worked over the connected separated switch with DeOxIt. Don't know what the problem was but I reconnected it and it works using the AU717 as a pre!!!

Thanks all!!

Next up...Sansui Eight receiver (first time I will restore one of these)....wow what a tank!!
 
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