5150 / JJ Tubes

[twotonmidget]

I've read in a number of places, including on this site that JJ Tubes are the way to go for a 5150 head. So I replaced my worn out tubes with a new set of JJ's. Initially, all was well, but after a short time, there was a loud hum that would go in and out anytime the amp was turned on. I have come to find out that the JJ tubes fit very loosely in the sockets of my head. The Jan/Phillips tubes that I had in there fit perfectly, but for whatever reason, the JJ's fit so loosely that the connection goes in and out. The tech I took it to tried a different set of JJ's and had the same problem.

Do JJ tubes "run small?" It seems strange that a tube so famously "right" for an amp would not fit in that amp. Just to be clear, I bought the JJ 6L6 model. Has anybody else had a similar experience? Is there a way to fix it? Please help.

[Jerry P]

JJ changed the bases on their tubes 6-8 months ago and the pins are just a tiny bit small. It's just enough to cause problems with tube socket connections. They work fine in certain types of tube sockets, but not the sockets used in the 5150. I don't use JJ's anymore because I had too much trouble with them here in the shop. I use either Svetlana or TAD 6L6's in the 5150's now.
Jerry