Sansui AU-719 buzzing

You will often see that as time progressed in Sansui manufacturing. Typically great components, but as it got later in the 80's they went to pressboard chassis, and the dreaded black plastic. :thumbsdn:

Indeed.

I've seen some of their early/mid 80's entry-level stuff and it is quite terrible. The pressboard bottom panel took my breath away (for all the wrong reasons!)
 
Great to hear about the terrific restoration Hyperion was able to do, and the tracking down of that buzzing. Amazing how often these kinds of problems are due to soldering flaws.

I've heard nothing but glowing satisfaction after restorations like these. I have an AU-719 that is totally original, but working really well. Once I've gotten other things cleared out of the way, I plan to embark on a restoration... if I'm in good financial shape, I'll send it off to someone skilled to do it, otherwise, I'll have to try my own hand at it.
 
Number 13 is a picture of the completely re-capped phono amplifier. Note that I did not use 'open frame' type trimmers and opted for Bourns multi-turn types. This is in spite of the fact that it makes adjustment of the phono offset a bit more difficult. Notice that I have pitched up the front of the lower trimmer so that it can be reached with a long trimming tool (instead of through the hole in the board from underneath as with the old open frame trimmer)

Well that's about it - I did take a few other pictures but not of much interest really.

Lastly
I added 4 x 2.2uF film caps located across the 4 main smoothing capacitors - in the same style as with AU-717/517.

I see in this picture that the 22pf Black Flag capacitor is still showing on the completed board. Was it ever eventually replaced along with the other 3 black flags in this AU-719 ? Or was this work done before anyone was aware of the potential black flag issues, as this is an older 2011 thread ? I am getting ready to replace the 4 black flags in my own AU-719 with the proper 22pf ceramic capacitors, so just wondering about the status of this AU-719 as well. The rest of my AU-719 was completely restored, but when I received it a couple of months ago after purchase, it still had the black flag capacitors. So it seems that not every respected tech knows about these black flag issues, even to this day. I know Hyperion is now aware due to some posts after 2011 and that he helped me pick out the correct 22pf caps for my own AU-719 replacements. But just wondering about this AU-719 and if it was working ok with the black flags if they were not replaced yet.
 
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Was it ever eventually replaced along with the other 3 black flags in this AU-719 ?
Well spotted, yes, they were replaced, except perhaps for the first 20 years of their life the Black Flags have always been an issue and because of their function (namely 'stability'), they should be replaced wherever found.
 
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Well spotted, yes, they were replaced, except perhaps for the first 20 years of their life the Black Flags have always been an issue and because of their function (namely 'stability'), they should be replaced wherever found.

Hi. I haven't been on audikarma for some time but I had bookmarked these discussions regarding the restoration of an AU-719. I have a well kept au719 of my own which I bought 6 years ago. It still produces incredible sound, currently driving a pair of KEF LS50s. It's only minor faults are the volume pot's a little scratchy while rotating and I suspect the bias offset needs adjusting as the power protection seems to cut in a little early.

Before I fiddle with it to sort out those couple of issues I thought perhaps it's time I gave the old thing a full going-over. I'd always meant to but have been too busy enjoying it. Are you still working on amps like this and would you like to take on a restoration ? If not, or too busy perhaps you could point me towards someone else who could do a good restoration.
 
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