Ceriatone Forum

Hey everyone,

I got my OTS about 1.5 weeks ago and love it but I've encountered a problem. When I got it, I put some Winged C 6L6GC's in it and they were nice but after playing decently loud for about 2 hours, I got this light static-like buzz on certain notes (even clean). I tried everything, different guitars, klein, no klein, effects, no effects, different cables until I finally figured out it was the power tubes. I replaced them with the JJ 6L6GC's I got from Nik and I've been playing at low volume for a week (I really liked the JJs btw). Today I got to turn it up, nothing too loud, mostly clean, some disto from pedals, and again I just got the static after about 2 hours. I think the power tubes went out again. Is there somethig wrong with my amp or am I doing something wrong that I'm blowing tubes like that?? I did put it on standby for a while before turning it on. It's kind of discouraging because I've only played it loud a few times and I've blown like 75$ worth of tubes. I'm using a Kleinulator with all knobs set around 3 o'clock and I don't have a head cab. I've tried everything (switching variables) and I've narrowed the problem down to the amp itself, not wires or the klein or anything. Obviously I can't test the power tubes because I've blown them all but its 100% the same problem as the first time the tubes went south.
Does anyone know what the problem could be? Anyone had the same issue? I've emailed Nik about this too.

Thanks,

Alex

Did you set the bias for the tubes?  If it's set too high the tubes won't last long.

"Posted by: gbergl   
Did you set the bias for the tubes?  If it's set too high the tubes won't last long."

No, I haven't touched that because I've never biased an amp before. Perhaps it was accidentally set too high out of the box? I don't think I would have a way of checking that since I don't have the machine thing for it... hmm...

I'm guessing the bias is set with the knob post between the two power tubes? Maybe I could see how high it's set by "feel" if someone says something like "it should be turned half way up out of the box"?

Do you have a multimeter?

If you do... set it to the mV. You have bias test points besides the power tubes. Your bias should be around 35mV.

And if it is biased too low - the tubes are running 'cold' and the overdrive they produce at higher volumes, will be very harsh like and old transister radio, which could be what ou describe as a light static-like buzz .

Anyway, the amp should be re-biased for every set of powertubes, so get that multimeter out and get biased.

Thanks to hywelg a Noob bias guide

Turn the power on, take it off standby and let it warm up for 5 mins or so. (however if this is the first time with a different set of tubes ie a change from 6L6 to El34, don't wait, get the bias into the right ball park staight away)

Turn master and volume down to 0.

Turn on your multimeter and select volts (DC if its not autodetect) (mV across the 1ohm resistor = mA)

Plug black probe into black socket and red into red. You might have to hold them to make contact if they don't fit well. Take the reading. Then move the red to the other red socket. If the valves are matched the readings should be similar.

Use the pot to get where you need to be, keep checking both sides. Play it. Try it hotter or colder within reason, find you're own preferred bias.

Thanks for the help guys. It looks like I have to buy a multimeter :P Any tips on shopping for a cheap one? Any will do?

any with milivolts will do

Sorry if this is redundant or beginnerish, but please be careful poking around an amp that is powered up. Don't touch a THING!