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Speaking of JJ Tubes

11/26/2005 8:12 PM
Rick Erickson
Speaking of JJ Tubes
I've noticed recently that some JJ power tubes, (maybe all of them) particularly the 6L6 and E34L tubes have pins that are slightly smaller diameter than most NOS USA or Russian brand tubes. This can cause big problems if the tube sockets aren't re-tensioned before installing the new tubes. Anyone else having problems with intermittent sockets when installing JJ tubes? Love the tubes, hate the bases.  
PS - this is just one good reason to have one of those cheap digital calipers on your bench.
11/27/2005 11:33 AM
How much smaller are they? That's a strange thing to go non-standard on.
12/1/2005 3:13 PM
Rick Erickson

"How much smaller are they?"
A quick check of a couple tubes reveals:  
A standard USA type octal socket pin measures about .094" and has a taper to it at the end. The JJ pins are straight (no taper) and measure between .087-.090". Just enough difference to make them fit loosely in the sockets. I have found this to be a problem in several amps I've retubed lately. Re-tensioning the sockets takes care of the problem but it's a drag to have to do that every time I use my bias probes and then re-install the tubes.  
12/9/2005 9:50 AM
I had a JJ 6L6 light up like a christmas tree due to the sockets on my '68 dual showman being old. I replaced all the sockets after they were unable to retension and now it works fine. weird though, I had never thought about it being because the pins were smaller.
12/9/2005 12:53 PM
Rick, I've also noticed this problem. At first I thought that the sockets were bad because I pulled the tubes out many times, but then I put in some JJ 6L6GC that I bought about 6 months ago, and they felt just right when I pushed them in the sockets.  
12/10/2005 9:42 PM

In addition to this, I've just noticed that the pins are _shorter_ as well. I was putting a new JJ ECC83S in a new amp the other night and the pins barely went into the socket far enough to really seat. I pulled it out and compared it with the OEM Chinese tube and the JJ did indeed have measurably shorter pins.
12/12/2005 4:49 PM
Frank De Salvo

I've noticed the pin issue, as well...I haven't bought any of these JJs for some time; I think they kill the sparkle and top end of the amp.  

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