6550 Tube Blew - A Few Questions

Yea, I was hoping it was something simple like that. It fooled me, happening right after the tube blew. I guess I learned a little about my amp, though. Thanks a lot!

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

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?

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

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

07-05-12: Marakanetz
When I owned VTL MB100 in this unit tubes didn't die 'piecefully' and once a goo chunk of PC board was fryed.

Thanks for the info. I can certainly solder in a resistor, but I need to know which one. I guess the first step would be to get a new quad of tubes, so I can see what is working and what isn't?

Then I can decide whether to ship it somewhere or open it myself. I like the sound of the amp, but if tube amps are _this_ much trouble, maybe a good SS amp is the way to go. :)

Terry

I have an analog meter. In fact one of the noticeable things about this tube that blew was the shaky needle of the meter when biasing it. It was the only tube that wouldn't stay constant but would go like a pendulum from a low to high voltage and back again. I guess it was getting ready to go.

I could certainly change a resistor, I'm not a stranger to a soldering iron and a PCB, but I've no idea what I'm looking at, without some assistance. I don't even know if the amp has been affected beyond the blown tube. I guess I'll order some new tubes and see what happens.

Hey, that was a great post. I think I found the resistors you said on Ebay (who has 50 watt resistors lying around? :) ), and I'll start on these tests as soon as the tubes arrive. Thanks a lot!

Terry

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?

It's the front switch. :0