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Sansui AI-317 mk1 - Troubleshooting and Repair

Question is why you have positive value in place of negative. This negative voltage must get there directly from negative lead of C604. I already forgot but is there a jumper wire to the common point of R53, R54 ?. May be those were mixed up somehow?? Accorging to Service Manual there should be some kind of a jumper wires from big caps to the R53,R54 and positive to R47, R48.
 
Verify that point F connected to NEGATIVE of C604 (you will find point f near big caps) and point e connected to positive of C603(again near big caps) also verify points c and d connected to the corresponding c and d (those are ground points). Check for bad solder joins.
 
yea i just looked at the pics of AU-317 and there are 2 wires coming from big caps to those r53,r54 and r47,r48 (orange and red) and also 2 black wires going to points c and d.. Check them please.
 
TupolevFan said:
Question is why you have positive value in place of negative. This negative voltage must get there directly from negative lead of C604. I already forgot but is there a jumper wire to the common point of R53, R54 ?. May be those were mixed up somehow?? Accorging to Service Manual there should be some kind of a jumper wires from big caps to the R53,R54 and positive to R47, R48.
Click to expand...
Good question. There is evidence of someone being in here before me. I will investigate this and your other suggestions and report back
 
TupolevFan said:
Verify that point F connected to NEGATIVE of C604 (you will find point f near big caps) and point e connected to positive of C603(again near big caps) also verify points c and d connected to the corresponding c and d (those are ground points). Check for bad solder joins.
Click to expand...
YES!!!!!!

I got a relay click!

So you were right to suspect wire connections from C604. What had happened was the solder joints under the negative big capacitor were a mess and the solder pad had lifted from the circuit board. this was only noticeable if pushing down on the top of the cap while looking at the underside of the board.

I removed all the solder and re-soldered the connections. I had to scrape some of the coating off of the trace that had the wire connections and make the solder flow onto that to complete the connection.
 
I suspect whoever had worked on this amp before me had flipped the amp so that the full weight of it was resting on the big capacitors, causing the connections to separate from the board on the other side.

I will check the bias again now
 
troutmaskrep said:
YES!!!!!!

I got a relay click!

So you were right to suspect wire connections from C604. What had happened was the solder joints under the negative big capacitor were a mess and the solder pad had lifted from the circuit board. this was only noticeable if pushing down on the top of the cap while looking at the underside of the board.

I removed all the solder and re-soldered the connections. I had to scrape some of the coating off of the trace that had the wire connections and make the solder flow onto that to complete the connection.
Click to expand...
Well done!! That sort of fault can be frustrating to find, persistence and patience pays off!
 
@skippy124 @TupolevFan and the many others that chimed in - thank you!!

I learned a lot going through this exercise with you and would have never figured it out on my own.
I'll check the bias and see if this thing can actually makes sound next. I have a pair of disposable speakers to test with - this amp isn't going near my good speakers until it has been restored.
 
Don’t forget to check the DC offset as well. The DC offset can be relatively high and still have the speaker protect relay engage. By relatively high I mean up to and around 0.5VDC which will make a significant pop when the relay engages if the speakers are selected already, of if the the speakers are selected (switched on) after the relay engages.
 
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