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In the Forum: Melquiades Amplifier
In the Thread: A different breed of 6C33C amplifier.
Post Subject: You are not lucky with them.Posted by Romy the Cat on: 10/4/2011
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 KOTriode wrote:
Romy,
The normal bias for the Golden Grid tube for 200V Plate at 200ma is about 70V-80V for the good tubes, the bad tube read 0ma at this bias, when drop to -30V it start reading some current, but can't get to 150-200ma current for the SE amplifier.
The people who make the OTL amp that I talked to also see abnormally higher number of new 6C33C tube out of spec and unusable than other Russian tube such as GM70, pentode family. He also added that he has seen an OTL amp used in a store played 18 hours a day every day and the tubes lasted for 3 years.
 
I do not remember correctly but I think a normal bias for 6C33C is 55V-80V but if you have at 30V juts some current but not a good 0.5A then something IS wrong with the tube. This is very strange. KOTriode, you are understood that I am not in the business of support of the 6C33Creputation. Still, I can only report what I observe and I did not observe any problem with this tube. I did also observed very sever abuse of this tube and the situation when the tube refused to die. The GM70is VERY different tube, triode not pentode and GM70 is much more reliable tube and stable in characteristic, in fact it is the most stable then probably any other, but what it has to do with anything?  I do know people who have 6C33C running in amps days and days. When I had 4 ML2 I sometime did not turn them over long weekends – it is 8 tubes. I run Mils with 8x6C33C for days and I find the 6C33C is very reliable. In my view the problem with reliable is not reliability by stability of parameters and high run out of characteristics with new tubes. Anyhow, I am sorry that you look like not so lucky with those tubes. BTW, the Bulgarian guy told me that all of his tube are pulls, not the new tubes…
 

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