ARC CA-50 tube changing

Problem solved! I learned that my local second-hand audio dealer has lots of experience changing and biasing the ARC tubes. Echo Audio in Portland.

Thanks guys, i don't want to risk getting fried...

I had a CA-50 and bias setting was not too hard, just remember the high voltages involved and be careful!

Well that stuff runs at high voltage i.e. 420Vdc on the plates and screens. You can't just stick your hands in there. You need the proper probes to measure bias voltage drops. Make one wrong move and poof, the outcome will not be pretty. I would suggest to let an authorized ARC tech. take care of that for you. If the boards weren't vertical, you probably could have done it yourself

Yeah, it's kind of hard to see anything in there with the big 6550s glowing sideways and the boards mounted vertically on the sides. Still, if a tech can do it then why can't I? I just need some instructions...

Seeing as that is an integrated amp it might be a bit tricky as the board might be mounted vertically. This may make access the test points tricky. Do you see any bias pots? There should be at least one per channel.