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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
128x128rwinner
rwinner's avatar
rwinner OP
37 posts
 
Well, I got the replacement tubes today, replaced the right channel with them, and am not getting power at all.

I checked the fuse, and it was still good. I checked inside, and could see no obvious damage or the smell of something burnt. What are some of the obvious things I can check before I bring it in for out-of-warranty repair?
marakanetz's avatar
marakanetz
5,473 posts
 
Did you ID the bias resistor as mentioned above?
I believe that you have 2 tubes per channel and bias resistor is shared between two tubes. It's realy not hard to ID low-resistance resistor and test it for open circuit.
rwinner's avatar
rwinner OP
37 posts
 
I thought of doing that, but I understood you to say that the bias resistor would not prevent the amp from turning on. I;ve already checked the filaments on the tubes, and they are intact. Should I also check the bias resistors?

Terry
marakanetz's avatar
marakanetz
5,473 posts
 
Blown bias resistor would prevent tube or pair of tubes(for push-pull amp) to turn on.
rwinner's avatar
rwinner OP
37 posts
 
Just checked the bias resistors. They were easy to spot - 5 watt 10 Ohm jobs. They tested for 10 ohms, all 4. I tested them out of the circuit. What else might I check?
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