A classic power amplifier from the 80's. What a beauty!

[KhronX]

A few weeks ago, my girlfriend got her mits on a freebie Yamaha AX-930 from the early 90s, "on my behalf"  (ie. sent me a photo of it and asked if i wanted it  )

For once, the <ahem> "marketing wank" might be considered as being in the ballpark of honest advertising 

Specs & co: http://www.hifi-wiki.de/index.php/Yamaha_AX-930

[taydin]

Wow that thing must have been running in an isolated environment with air filtering :O No dust and rat piss at all ...

[KhronX]

Maybe not visible in the photo, but it did have a little bit of spider-web in the rear right corner, and a couple dead bug corpses under the front panel, but all in all, not bad for over a quarter century, indeed 

[taydin]

Finally got around working on my classic amp. I borrowed a wire wrapping tool so that I can restore the amp in its original condition.



And then I started assembling the PCB's to the frame



And finally re-did all the wire wrapping

[taydin]

The unit was now in a state where I could power it up and apply a test signal. I did this and I was getting no output.

I had already found the schematic of this unit. Checked the power rails, all were good. Started tracing the signal from input into the amp and found out that the pre-amp doesn't output anything. The pre-amp was not getting 24V power.

I following the pre-amp power to the main power supply, and, not surprisingly, the BD135 that was removed and mounted to the chassis was a single transistor regulator, obtaining 24V from +40V. And it was bad. The schematic says that it is a 2SC1449 and the closest equivalent that was available here was BD377. So I replaced it with that and also inserted a small heat sink.

Re-tested after installing new transistor, and I was getting output from the amp!

[taydin]

Testing the repaired unit with a spotify media player, which is another project I'm working on.



I remember this amp having a great sound, and I was really pleased to hear it after this long. I love it