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Sansui AU-719 possible relay fault?

RR-- said:
Also apologies but I seem to have misremembered two details, this amp has a 220V sticker and originally came with four 63V 12000uF capacitors,
Click to expand...
No apologies needed. Was just wondering if this was some kind of Frankensteined amplifier because of the mixed parameters. Still strange that a CSA model has the multivoltage transformers.
Let's just hope you found the culprit and you can start enjoying your AU-719 again
 
OK. Looks like D03 is shorted. To make sure you will need to desolder it from the circuit and remeasure it. Also did you measure in both direction ? i mean when you test the diode you need to measure 2 times each diode. Other words measure in forward direction and you will see forward voltage drop and in opposite direction where you should see "OL" or very high resistance. You should replace ALL of those rectifiers. Will discuss options later.
 
TupolevFan said:
OK. Looks like D03 is shorted. To make sure you will need to desolder it from the circuit and remeasure it. Also did you measure in both direction ? i mean when you test the diode you need to measure 2 times each diode. Other words measure in forward direction and you will see forward voltage drop and in opposite direction where you should see "OL" or very high resistance. You should replace ALL of those rectifiers. Will discuss options later.
Click to expand...
Yep I measured both ways to be sure it wasn't another board orientation misprint as this amp does have one already, measured backwards they all just said OL. I'll try removing and retesting it tomorrow.

On the sides of these rectifiers there's also some writing: SS-3R_9 216 (in black), SS-3_9 227 (in red), SS3R 9 224 (in black), SS-3_9 227(in red)
 
RR-- said:
On the sides of these rectifiers there's also some writing: SS-3R_9 216 (in black), SS-3_9 227 (in red), SS3R 9 224 (in black), SS-3_9 227(in red)
Click to expand...
Yes that's just the rectifier type and polarity - SS-3 is the standard polarity and SS-3R is the reverse polarity, the different text colours are an additional aid to identifying which is which. (probably mostly for original assembly purposes).
 
Guys,

Re the confusion re the filter cap values and the CSA variant, the unit here in question is a multi voltage international version, it has the internal voltage selector for 110/120/220/240VAC input voltage selection (CSA is fixed 120VAC input), and the mains transformers fitted are multi voltage types (6 input wires on mains side). My son picked up 719 a few years ago - international voltage model, and it was factory fitted with Elna 12,000uf 63V. I have at least one in the storage rack, if I get some spare time I’ll pull the covers and see what is fitted.

Now the service manual isn’t very helpful here either, if you look at the last page in the service manual PDF that is commonly available, the parts list for the top view has only one part number for the mains transformers - there should be four part numbers, one for CSA version, one for BS/EU version, one for AS version, and one for international version shown in the main schematic. Note also that the filter cap value shown in the same list shows 12,000uf 63V. Confusing to say the least……. And there are other anomalies in the power supply schematic…….

Back to normal programming…..

Cheers
John
 
Last edited:
skippy124 said:
Guys,

Re the confusion re the filter cap values and the CSA variant, the unit here in question is a multi voltage international version, it has the internal voltage selector for 110/120/220/240VAC input voltage selection (CSA is fixed 120VAC input), and the mains transformers fitted are multi voltage types (6 input wires on mains side). My son picked up 719 a few years ago - international voltage model, and it was factory fitted with Elna 12,000uf 63V. I have at least one in the storage rack, if I get some spare time I’ll pull the covers and see what is fitted.

Now the service manual isn’t very helpful here either, if you look at the last page in the service manual PDF that is commonly available, the parts list for the top view has only one part number for the mains transformers (there should be four part numbers, one for CSA version, one for BS/EU version, one for AS version, and one for international version shown in the main schematic. Note also that the filter cap value shown in the same list shows 12,000uf 63V. Confusing to say the least……. And there are other anomalies in the power supply schematic…….

Back to normal programming…..

Cheers
John
Click to expand...
Sorry John, I was confusing my old 8080 filter caps with my AU719's 12,000uF 63V caps, I think you or your son was the one who recommended these specific 15,000uF Gold Tunes caps back in 2013, I was very much inspired by your son's rebuild thread haha.
 
RR-- said:
Yep I measured both ways to be sure it wasn't another board orientation misprint as this amp does have one already, measured backwards they all just said OL. I'll try removing and retesting it tomorrow.

On the sides of these rectifiers there's also some writing: SS-3R_9 216 (in black), SS-3_9 227 (in red), SS3R 9 224 (in black), SS-3_9 227(in red)
Click to expand...
Wait you said All of them were OL in reverse? What about the one that was shorted (D03) ?
 
skippy124 said:
Guys,

Re the confusion re the filter cap values and the CSA variant, the unit here in question is a multi voltage international version, it has the internal voltage selector for 110/120/220/240VAC input voltage selection (CSA is fixed 120VAC input), and the mains transformers fitted are multi voltage types (6 input wires on mains side). My son picked up 719 a few years ago - international voltage model, and it was factory fitted with Elna 12,000uf 63V. I have at least one in the storage rack, if I get some spare time I’ll pull the covers and see what is fitted.

Now the service manual isn’t very helpful here either, if you look at the last page in the service manual PDF that is commonly available, the parts list for the top view has only one part number for the mains transformers - there should be four part numbers, one for CSA version, one for BS/EU version, one for AS version, and one for international version shown in the main schematic. Note also that the filter cap value shown in the same list shows 12,000uf 63V. Confusing to say the least……. And there are other anomalies in the power supply schematic…….

Back to normal programming…..

Cheers
John
Click to expand...
Good to know it's not an anomaly.
Was just worried some importer took an international multivoltage model and fitted it with 63 volt caps having an CSA example. As you say, the service manual is not always to be trusted.
I am still wondering what his rail voltage is. According service manual the " standard model" has 63volt which would not blow up your capacitors but will wear them down a lot more.
As has been suggested, I would just desolder the wires to the left channel main capacitors to rule it out that they are feeding the protection.
Now it appears rectifiers are ok?
Mystery continued . . . .
 
GrisPato said:
Good to know it's not an anomaly.
Was just worried some importer took an international multivoltage model and fitted it with 63 volt caps having an CSA example. As you say, the service manual is not always to be trusted.
I am still wondering what his rail voltage is. According service manual the " standard model" has 63volt which would not blow up your capacitors but will wear them down a lot more.
As has been suggested, I would just desolder the wires to the left channel main capacitors to rule it out that they are feeding the protection.
Now it appears rectifiers are ok?
Mystery continued . . . .
Click to expand...
No it appears D03 has a short
 
Anyway for you plan is to desolder D01 and measure it outside of the circuit and Desolder D03 and measure it outside. in total you will do 8 measurements. (4 forward and 4 back ). But i think we found the issue.
 
I got fairly lucky with my Au719 as it was a one owner and completely stock and rust free when I got it so I don't think we need to worry about any shoddy work. (That's not my own doing) My 8080 on the other hand was a dumpster fire from the previous owner and full of rust but it's singing daily now.

I removed D01, D03 and remeasured the other rectifiers still soldered in place with some different results

D02, D04

Standard 0.495V
Reversed 0.768V
Standard 0.493V
Reversed 0.767V

D05, D07

Standard 0.514V
Reversed 0.722V
Standard 0.528V
Reversed 0L
Two inside legs 0.990V

D06, D08

Standard 0.495V
Reversed 0.725V
Standard 0.495V
Reversed 0.725V
Two inside legs 0.001V Both ways


With the D01, D03 (SS-3 9 227 in red) rectifier removed I was wasn't sure exactly which 8 ways I should be measuring it so I just did every possible combination I could think of, it seems like one side is definitely dead though. Here's a heap of photos of the results.


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Looks like Ike one of them is shorted for sure. So lookes like TupolevFan made the correct diagnosis.
Really interesting stuff. And let's hope you can replace that easy.
So although robust they do fail sometimes.
 
GrisPato said:
Looks like Ike one of them is shorted for sure. So lookes like TupolevFan made the correct diagnosis.
Really interesting stuff. And let's hope you can replace that easy.
So although robust they do fail sometimes.
Click to expand...
I wonder could this part's failure be caused by another faulty part higher up in the chain? Would replacing this and nothing else just cause the replacement to instantly fail?
Hopefully it's just this part that's faulty because other than powering off strangely the amplifier sounds great.

I think my next question is if this part is in fact the cause of the problem what should I replace it with?
 
RR-- said:
I wonder could this part's failure be caused by another faulty part higher up in the chain? Would replacing this and nothing else just cause the replacement to instantly fail?
Click to expand...
Can be but on the other hand even really robust and reliable parts will have some small % of failure, especially after +40 years of service.
 
GrisPato said:
And as I remember Sansui even provided PCB holes with solder pads to replace them with single diodes
Click to expand...

Looks like I should have waited before ordering those transistors recommended earlier in this thread, each Mouser order is like $5 worth of parts and $25 worth of shipping haha.

Here's a photo of the place I desoldered the rectifier from and the additional holes.

Some more questions, if D03 needs replacing I may as well do all of them, could someone be kind enough to recommend what I need to order and where to put them exactly? Would the reverse polarity rectifiers need a different part or just the same part reversed? Why would they originally use these parts instead of the through hole style anyway?

PYXX5l7.jpg
 
You could use something like this
https://www.mouser.com/ProductDetai...tor/P600G-E3-54?qs=E3OxquYwg8GHBUeqJys%2BEA==
or
https://www.mouser.com/ProductDetai...=sGAEpiMZZMtbRapU8LlZDwOXpTTbNuB/eh6XQVNqMUY=
or
https://www.mouser.com/ProductDetai...=sGAEpiMZZMtbRapU8LlZDzCgIkNleXIZFCQGdZe/kbU=

but you will need to be creative.
What i would do is to keep the U shape frame, remove the original diode in such way (if possible) that U shape would still be monolithic ( I mean try not to remove original diode in a way that it would create huge hole in a U shape),
then i would drill a hole just to fit the lead of a new diode and solder it to the U shape. So you will need 8 diodes.
 
So just to check two things, would it be possible just to put those diodes onto the board without the U frame bracket? like in this picture?

C1JBjQh.jpg


Does the bracket serve a purpose other than a heat sink?

I think I might order these https://au.rs-online.com/web/p/schottky-diodes-rectifiers/9170751 if you think they'll work and either just replace the two if they fit or dremel/drill open the old brackets and try and retrofit the new rectifiers into them.

Thanks again for all the advice here.
 
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