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Sansui AU-919 Needs Love.

Finally have the capacitors to replace the insides of the oval caps. Took some inspiration from an old post by @Hyperion and bolted the leads to the aluminium tag on the 'lid' of the cans. Three are finished with one more to go.

Should I put some silicone around the aluminium tags I have bolted to to keep them from oxidising?

Going well so far.
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Hyperion said:
I don't think I did anything about this, I just made sure the surfaces were clean and then done up good and tight. ;)
Click to expand...

On my first one I bolted it finger tight just to see what length to trim the wires to before attaching them to the capacitors. Took a quick reading to make sure all was well and got an esr reading of 1.6 ohms nearly had a heart attack. Quickly realised the the bolts were loose and after tightening all was well.
 
The main filter capacitors are just waiting for some shrink to finish them off. Ordered some from china last week, $7 for 1 meter and free shipping, hope it fits.

It is time to swap over the cables from the damaged F-2845 board to the replacement one.
Just one small problem to fix first.
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Used a rivet to give a secure connection and put some solder mask over the exposed trace. Next time I will put the mask right up to the edge of the rivet so there is not such a big blob of solder on the joint.

Not pretty but it should be robust enough.
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I have all the parts I need for a recap but doing it now before getting it working first would be madness for me.
So in the coming days I will replace only the 32 or so black flags, measuring them incase some have a story to tell.
Then it will be getting close to fingers crossed time.
 
Hi Alex ,
Nice work there !
I was wondering if you came up finding “appropriate” TO-3Ps power transistors for your restoration ?
 
Alex22 said:
Actually I still need to find four 3.5mm nuts.
I saw one of your posts with a conversion from soldered connections.
This replacement board came like this, which is why I don't have nuts to fit, yet.
Click to expand...
Idea:- Change them all for M3 (or M4) - perhaps a bit more common?..... I like that the terminal securing nuts you have are 'Nyloc' nuts - very good idea - the others can be plain nuts of course.
 
Hyperion said:
Idea:- Change them all for M3 (or M4) - perhaps a bit more common?..... I like that the terminal securing nuts you have are 'Nyloc' nuts - very good idea - the others can be plain nuts of course.
Click to expand...

Yes.
I have plenty of M3/M4 nuts and bolts. I also have M4 Nyloc nuts if I have to change them.
But I will see if I can find ones to fit first, shame to have to desolder the terminals for the sake of a couple of nuts.
 
First up for black flag replacement is F-2841.
C35, 36, 37 and 38 are 3pF and unfortunately I don't have a tester that can test such low capacitance.
C01 and C02 are 33pF and both read 31pF on my little tester.


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On to F-2839 driver board.

Replaced 14 capacitors. C23,24,25,26,53,54,55 and 56 are all 3pf so I can't test them at the moment.
C39 and C42 have been replaced sometime in the past and test at 31pF and 32pF. C41 looks original to the amp including one leg covered in glue and quite nicely corroded, measured 32pF.
C40 had been replaced in the past but measured 40pF, should be 33pF.

Before
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After
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Interesting to see how they bent the collector lead of the left channel drivers, indicating they are replacements, should be 2SB536/2SD381.
Looks like this driverboard has the 220uF decoupling/ local filter capacitors.
 
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2 transistors have been replaced on one channel so will have to take a closer look. 2 resistors have also been replaced. I have some detective work to do.
 
GrisPato said:
Interesting to see how they bended the collector lead of the left channel drivers, indicating they are replacements, should be 2SB526/2SD381.
Click to expand...

Yes I haven't taken a good look at them yet, if they are acceptable they can stay until I have her running. Then I expect that I will be swapping them out when I recap it.
 
If they are the B536/D381, they are the correct replacements. Same transistors as the B537/D382 which where from factory made for horizontal installation with base and emitter leads bent and collector lead cut.
 
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