Sansui AU-919 Needs Love.

[Alex22]

I have some time on my hands this week so pulled out the 919 that has been sitting in a cupboard for the last year. Got it as a non working unit so fun games and learning ahead.
Apparently the previous owner intended to repair it but had too many other things on the go to continue, he passed it on for a fair price. I expect that the unobtainium transistors are not present, and almost certainly some are blown.
This is going to be a long slow thread.

So here is the first look.



Serial number suggests that it was made in December 1978.






So far it looks fairly clean and has most of the original parts.

 

[The Fuxtor]

Hyperion has a good thread on adapting a different case style transistor for outputs! Good luck

 

[AUD101]

Looks in great condition! - looking fwd to some AU919 2023 restoration fun!

 

[Alex22]

Looks in great condition! - looking fwd to some AU919 2023 restoration fun!

It will probably be a couple of months before I even get the parts.
For now it is just a look around to see how deep the hole is that I am digging for myself.

 

[rickb119]

Where are you located? Just wondering, as that's a 220v unit.

 

[Alex22]

Where are you located? Just wondering, as that's a 220v unit.

The 919 came from Canada so am not sure why it has a 220v stamp. I'm in Israel so it has done some traveling, I needed a unit that could run 220v.

 

[Alex22]

Ok so now I can see at least some of the problems. F2845 has self-destructed.

Bottom cover is also in fair shape.





Voltage is set at 110v. Need to change that and probably change the fuse from 10Amp to 5Amp 220'240v


Ok so some wires have been disconnected and things are looking toasty.


Houston, we've had a problem!!!!


Taking a wild guess here but I think the melty burned bits are trying to tell me something.

 

[rickb119]

Looks like you've got some work to do. Good luck.

 

[Alex22]

Ok so here is one small piece of luck. The fine gentleman who supplied this 919 went as far as getting a replacement for F-2845 and recapping it, looks like he has given it upgrades in capacities similar to others that have appeared on AK. I am hoping he did a good job and it is more or less ready to go.
I wonder if I may have a unit that came from one of our members.

 

[Alex22]

Next I would like to take a look at the unobtainiums.
Looks like a few screws and the oval capacitors should drop out.
Easier than a 517/717, though I bet it is one of the few things that is simpler on a 919.

 

[Alex22]

Well the oval filter capacitors are very easy to get out, lucky me.

C704 has an ESR of 0.30 12500uf
C705 ESR 0.24 13900uf
C706 ESR 0.29 12010uf

Now the fun one
C703 Open circuit

Well at least it makes the decision easy, They will have to have some nice new caps put in them.

 

[Alex22]

Finally a look at the output transistors.



So as expected NMC1012, NMA1012 are awol. Instead we have 2SD424, 2SB554. Don't know these but I suspect that they are not the best replacements. I removed most of the thermal paste to clean up a bit before testing. Expect some to be toast, we will see.

 

[Alex22]

My last post came out a bit jumbled, can't fix it.

Ok round about way.

 

[ghamilton]

 

[Alex22]

So I have observed a couple of things from this little adventure inside the 919.

On F-2845 D02 burnt out, question is why?

The oval filter capacitor C703 is reading as ‘open circuit’. did it take out D02 or vice versa.

Left channel output transistors look like they were replaced, possibly some blew with D02 and C703, no way to be sure but likely.

Have a replacement for F-2845 so some problems already solved for me.

Most boards have original components so she is rocking what looks like a full compliment of black flags.

I wonder how many other components are involved in this unfortunate chain of events?

 

[Alex22]

I am hoping that the installed 2SD424, 2SB554 output transistors will do for sacrificial duty, any reason not to use them?

i would love to use original transistors but finding a set of NMC1012, NMA1012 is not likely to happen. Most suitable T03 replacements are also no longer manufactured, hard to find and I don't want to risk ending up with fakes.

So from what i can gather 2SA2223A/2SC6145A T03P's may be my best shot. In the end I would rather adapt these to fit if they give the best currently available compatibility. Colour me shocked to find that these are no longer produced and we are now in while stocks last territory, again!

Anybody have thoughts on the 2SA2223A/2SC6145A path and/or do i have better options?.

 

[ghamilton]

The best thing to do is to study some of the recap threads on the 919.
You can probably find a lot of answers to your questions by doing so without us having to repost it.

 

[Alex22]

The best thing to do is to study some of the recap threads on the 919.
You can probably find a lot of answers to your questions by doing so without us having to repost it.

I have read all of the threads I could find, I'm just asking for a second opinion to be sure.
I'm insecure like that.

 

[ghamilton]

Maybe I missed it, but are you up to doing this? I mean have you had any experience soldering and such?

 

[Alex22]

Maybe I missed it, but are you up to doing this? I mean have you had any experience soldering and such?

You are correct I may mot be up to this. But want to give it a go.
I have recapped/restored 3 AU-517's an AU-717 and an AU-555A.. Different beasts complexity wise but my soldering is passable and I'm up for a few head scratching moments.
I wouldn't even try if it wasn't for these forums.