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Sansui AU-719 possible relay fault?

RR-- said:
Does the bracket serve a purpose other than a heat sink?
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Yes, it completes the connections to make the 4 single rectifiers into a 'Bridge' formation. I think I would dispense with the brackets and mount the new rectifiers in the PCB holes, maybe elevated off the PCB a few millimeters. You have the discrete rectifier polarities conveniently marked on the PCB and an indication of where links should go to complete the circuit if not using the brackets. (as Gris pointed out).
 
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Hyperion said:
Yes, it completes the connections to make the 4 single rectifiers into a 'Bridge' formation. I think I would dispense with the brackets and mount the new rectifiers in the PCB holes, maybe elevated off the PCB a few millimeters. You have the discrete rectifier polarities conveniently marked on the PCB and an indication of where links should go to complete the circuit if not using the brackets. (as Gris pointed out).
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Ohh i did not pay attention. And John is always good at it. I somehow looked at AU-710(aka AU-717) power supply which i am currently restoring for AK fellow. And there are no additional holes for those diodes. You are lucky to have those. I would choose diodes from the first link as they are beefy 6 Amps "gorillas" and Mouser has exactly 8 in stock (DigiKey has more but I am not sure if you have convenient access to DigiKey). So Get those and follow John's advice. You do not need brackets.
 
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TupolevFan said:
Ohh i did not pay attention. And John is always good at it. I somehow looked at AU-710(aka AU-717) power supply which i am currently restoring for AK fellow. And there are no additional holes for those diodes. You are lucky to have those. I would choose diodes from the first link as they are beefy 6 Amps "gorillas" and Mouser has exactly 8 in stock (DigiKey has more but I am not sure if you have convenient access to DigiKey). So Get those and follow John's advice. You do not need brackets.
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Oh ok that sounds great.
6A 400V seem to be quite a bit easier to find locally which would save me a months wait and expensive shipping, do you think these would be fine? If so I can pick them up locally this week.
https://www.jaycar.com.au/diode-6a4...bd52434a3ca8985069f9677352eb91&sort=relevance
 
Fixed!

Jaycar's pretty close to me an open on Sundays so I just bought some and soldered them straight into the spare solder points, I also made sure to install a new fuse. I haven't changed the other rectifiers just yet so I might put that off until they need replacing as well as the replacement transistors still in the mail from Mouser.

Here's a video showing it working like normal again.

https://drive.google.com/file/d/16DWymogD7gHQe7opza1VUi7qXMBwugu4/view

Thanks again for all the great advice here guys and a special thanks to TupolevFan, this was a really specific issue that had me stumped for months so it really is great to have it back up and running like normal!

URwiNQq.jpg
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Great!
This was a really interesting thread. And is really nice to see TupolevFan analysis, how in a few steps of logic reasoning he finds the failure. This is for sure going in my database.
I know who to send a message when I get stuck ;).
Also interesting that output stage still sounded good on just a halfwave rectifier on the left channel.
 
GrisPato said:
Great!
This was a really interesting thread. And is really nice to see TupolevFan analysis, how in a few steps of logic reasoning he finds the failure. This is for sure going in my database.
I know who to send a message when I get stuck ;).
Also interesting that output stage still sounded good on just a halfwave rectifier on the left channel.
Click to expand...
Yeah it was a strange issue, it happened about 4 months ago but I've just been ignoring it and still using it daily without any noticeable difference in quality.
I was a bit worried it might hurt my speakers when powering off so I've just been switching the speaker selector knob to the off position first to avoid the audible pop.
It's a fantastic sounding amp especially with these modern speakers, plenty enough power and then some, never once thought it needed a subwoofer to go with it.

Is this rectifier only for the left channel? I wonder what it does exactly because the left and right both sounded equal without any sort of imbalance.
 
RR-- said:
Is this rectifier only for the left channel? I wonder what it does exactly because the left and right both sounded equal without any sort of imbalance.
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Yes, because you have a transformer for each channel ( can also be necessary when you have transformer with two secondary windings, one for each channel.) This one rectified the AC from of the transformer for the left channel. I think it just proofs that a push/pull emitter follower outputstage has excellent riple rejection and there is no need to have ( as sometimes people try to "improve" there powersupply with) 2*40000/60000uF of filter capacitors. Although I think it is different with a full class A design.
And I think it would have been noticeable if it was the D609 (rb152) that is the rectifier for your pre amp powersupply.
 
GrisPato said:
Yes, because you have a transformer for each channel ( can also be necessary when you have transformer with two secondary windings, one for each channel.) This one rectified the AC from of the transformer for the left channel. I think it just proofs that a push/pull emitter follower outputstage has excellent riple rejection and there is no need to have ( as sometimes people try to "improve" there powersupply with) 2*40000/60000uF of filter capacitors. Although I think it is different with a full class A design.
And I think it would have been noticeable if it was the D609 (rb152) that is the rectifier for your pre amp powersupply.
Click to expand...
Hmmm I'm wondering now if I should do the other side so it's symetrical parts wise, that's a decision for another day I think.
 
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