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In Reply to: RE: I'm kind of completely turned off of JJ tubes now posted by DewDude on April 26, 2017 at 06:54:00
Well, it sounds like I'm not the only one. There was a series of events that has lead to this, so perhaps I'll give a background.
I bought these amps in autumn of 2011 on a whim. I was looking for my first tube amps and fell in love with them. They had the JJ 6V6S tubes in when I bought them. Ran fine for three years.
I then decided to swap in a pair of the Reflektor 6P6S tubes in each. They didn't die and ran for two years. One developed what I think is called hot cathode. Tube still works...but the entire cathode glows. That was when I went back to the JJ tubes.
Things were fine for about six months...then one amp developed low volume. The 5y3 was cold...so I swapped in a new pair. Then after discussion here....I ran something else because I liked the big bottles.
Two weeks later...a 6V6 dies...internal arcing. So I had a good pair of JJ and a good pair of Reflektor..so I stuck one of each in the amp and ran it.
No problems till Monday night. The amp was crankin out tunes....no problem. Then it quit. This is no big deal as I have a PITA interconnect I sometimes have to tap. That wasnt is...amp was dark. Fuse popped with smoke billowing out.1.2K resistor cooked.
So I took it to work and checked the caps and transformer. Not there. Our Eico said the 6v6 tube was fine.
Nope. It started smoking the minute I turned it on. Pulled the JJ and everything was fine.
Threw tube in the trash.
"Our Eico said the 6v6 tube was fine"
First, did you do the shorts test? It's not easy on an EICO, but you can test for shorts.
If it passed the shorts test, it was a short that only occurs with high voltage present. Testers test at approx 150V, amps run the plates and screens at 400+V.
Usually, in 6v6 types, it's a screen short.
The short test on this was merely moving the indicated knob to the indicated position. This was the first thing I did. It only had one test listed....so it was probably a screen short. I can't remember which Eico tester it is...my boss swears by the thing, I mostly swear at it.
If the workshop trash hasn't been emptied tomorrow and I can remember to do it; I'll retrieve it and put it through my Precision 612...which will short-test everything. Not that I really care...tube had a problem and was bound for the trash can anyway.
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