Strange problem after AU-999 rebuild.

[Robisme]

After I was done, the right channel didn't work. Switched speaker switch to C/separated and used a patch cable to swap right and left. Right channel works now but not left. So, I put the jumpers back in, switched to B speakers(none connected to B) and started tracing the signal. Everything seemed fine so I switched to A speakers where the speakers are connected and both channels are working. Played it for hours. Let it sit and tried again. Works fine.

I had cleaned the controls previously, and had wiggled them all with no change while the channel was out.

While it was not working I reseated all boards and poked around the wires with no change.

Now, I can wiggle boards, controls, and wires and it never drops the channel.

This happened with phono and aux. only inputs I tried. Rear level pots were cleaned.

My thought is the speaker select switch because it also is the pre to main switch. Cleaned it again.
Or, the tuner select switch. The lever was broken of so it may have taken a hit.

Any thoughts? Also, while it was not working I was able to set bias and DC.

Multi-turns installed. Sub-sonic filters removed. Tons of new transistors that are all proper.

Rob

 

[kevzep]

I'd say it's something to do with the speaker/pre-main switch, maybe there was a bit of crap floating around in there, and it needed a bit of working back and forth and sitting in different positions to solve the issue.....

I cant wait to get to the AU999 sitting on my bench at the moment, I really like working on them.. got this X1 to get going first.....

 

[Robisme]

Must have been. Thanks for the reply. Trying it again and it's working perfectly.

The AU-999 is nice to work on. Time to button it up.

This one got binding post installed. The owner uses banana plugs.



Rob

 

[kevzep]

Nice, I like those binding posts, very smart, I think I'll get something happening like that on the next one I do.

There are those who don't like them because if the risk of a short circuit, but, if you're using banana plugs, I don't see the issue...

 

[Robisme]

When I first installed a couple they were very close together, so I elongated the holes in the mounting plate and had to grind away some metal so the nut would not short to the back plate.
Filled the remaining of the elongated holes with epoxy.

Also had to careful so the negative posts don't touch the mounting bracket screws. If they sort to ground the balance check feature wont work properly.

Rob