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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
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marakanetz's avatar
marakanetz
5,473 posts
 
Forgot to mention that I prefer to bias amps on dummy load instead of speaker. When I owned VTL, I implemented switch to dummy load and used it even if I wanted to simply stand by the amp with no listening(only in case if I plan to listen to it multiple times per day).
rwinner's avatar
rwinner OP
37 posts
 
Ok, thanks for the info. I didn't know about the bias resistor blowing. I'll certainly call Jolida today and ask about it, and where I can obtain 0service if necessary.

Iirc, the same thing happened once before, and I didn't need to replace a resistor. But, I was thinking, if its just a resistor, shouldn't be too difficult to do myself if I can be told which resistor. Another reason to call Jolida and do some Googling.

Terry
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
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