6550 Tube Blew - A Few Questions


Hi. While listening to my system the other night, I noticed one of the power tubes for the right channel glowed extra bright, and static came through the speaker. I immediately shut down the amp, and haven't turned it back on.

Is it possible to check for damage to the other channel or other parts of the amp without installing a new tube to replace the blown one? I don't want to buy a matched pair and then discover that the amp has other damage.

Is it safe to test each channel with the other channel's tubes removed? Thanks!

Terry
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Showing 1 response by bifwynne

Dunno what amp you have, so take what I say with a grain of salt. It's possible that the 6550 arced and blew a bias resister. OTOH, maybe it would just be better to call the factory tomorrow and talk to the folks who know YOUR amp.

Ok, having said that, I'll tell you my tale. I own an ARC tube amp, which uses (8) 6550 winged C tubes. [As an aside, I later upgraded to the KT-120s.] Doesn't happen often, but maybe twice since I've owned the amp I've blown power tubes. Both times the tubes took out a bias resister which means that I had to call in my friendly ARC authorized service tech to replace the resisters. It's an easy fix.

Well, the last time I blew a tube, I called the factory and asked if I could run the amp without the tube or with a fresh tube even though I couldn't bias it. The factory said if I did, I would invalidate the warranty -- so I didn't.

In your case, call the factory. But I'm curious what would happen if you dropped in a fresh tube. If it biases, then maybe you didn't blow a bias resister and the amp might be good to go.

Gary (Hifigeek), an authorized ARC service tech, once metioned on the Forum that even if the bais resister didn't blow, the tube arc might have changed the resister's value. Another reason to ask the factory.

Good luck and let us know how you make out.