GE 5965 tube issues.

Sounds like a gear issue, unless the lower gain of a 5965 vs. 12AT7 or 12AU7 makes enough of a difference to cause an issue. Never had a signal tube fail on me, never had an issue using a 5965 where a 12AT7 (ECC81) is used. Since this was repeatable, I'd suspect the CJ and not the tube.

H9

Sorry Joe, you aren't giving enough info. So are 5965's what it takes from the factory in this position? No other tube filaments die other than this specific GE. How many other brands have you tried in the same position? Is it a 5965 or 5965A? If you are subbing for a 12AU7 (ECC82) then you can only use tubes that use a parallel filament. IIRC, the 5965A is a parallel filament tube but the 5965 is not.

H9

Still need more info like H9 said. But it does sound like a hardware issue not a tube issue.

I believe the you can adjust all the tubes in that pre but I don't think that is the issue It could be that it is over 20 years old and poly caps just like any other cap go bad in time. I would get it checked out and updated with new caps myself. It is an awesome piece of gear and deserves a new lease on life.

Why do you have a 5751 in a 5965 socket?

Joe, man I like you, but I can't understand most of your posts. I can't make heads or tails out of this thread as far as what you've done as a control to isolate the problem.

Good luck :cool:

H9

disneyjoe7 wrote: »

It seems to be a filament issue since this is what dies. Tubes filaments are wire together V4 to V8 and none other tubes seem to die?


Confused does output tubes die faster?

When I hear someone say "output tubes" I assume power tubes, there are no power tubes in a pre-amp, but I'm sure you know that. You don't say which position died here???? V4 or V8???? When you say "none [sic] other tubes die" are you referring to other tubes you have used in V4 and V8 position?????? Or do you mean no other tubes in the rest of the pre-amp die???? They are all at different points in the circuit and you could have an issue in one area that may not cause issues in another area.

disneyjoe7 wrote: »

When it died, and I found that the tube V8 5965 didn't light up I moved V4 to V8. And now V8 blow up again. But they are the same GE 5965 tubes. I think I remember that the V8 tube looked pretty light, could it had a bad tube? A tube with bad vacuum, blowing the filament? I have a 5751 tube in the socket and it doesn't sound bad, or look odd, too bright, or anything odd.

"When it died"??? When what died, V4 or V8 or both?????? Is V8 the one that died since you say it didn't light up??? So V4 was fine until you moved it to V8 and it blew up again, so I can deduce V8 position is the issue??? So you've blown two tubes in the V8 position??????? When you say "5751 in the socket", do you mean in V4 or V8 position which you should only use a 5965?????

See what I mean, I am so confused.

H9

Moving V4 to V8 might have moved the problem. I would replace both 5965's.

Never ever power up anything with tubes missing. It can cause all kinds of problems and literally burn up the piece of gear.

Get that 5751 out of the 5965 spot. They are not equivalent in any way what so ever. And you could be hurting the pre.

My guess is both went bad It probably started in the V4 position and V8 wasn't getting the voltage it needed and blew.

That is why they say you should always change tubes out in matched pairs or quads depending upon setup.

OK, my buddy says . . .

"I'd want to check the operating voltages on the tube.

Small signal tubes like 5965's should not change appearance much at all (difference in intensity of glow), and failing within several hours is extremely odd.

I'm thinking that perhaps the high voltage regulator has failed, which would result in the tubes being overvoltaged. The 5965's would bear the brunt of that as they're already set up for the highest amount of bias current.

The preamp would still make sound if this happened, but the noise levels and overall sound quality would suffer, as well as the life expectancy of the tubes.

The regulated power supply voltage should be around 320 VDC. If the regulator were to fail, it could jump to about 500V, way too much for the tubes as set up in that preamp."


Steve, PM me if you want to know where I'd send it for a checkup if it was mine.


P.S.: here's a link to the schematic if anyone else want to jump in . . .
http://drtube.com/schematics/cj/pv5.gif

Joe08867 wrote: »

I also wonder if something happened to the start up limiter. If that malfunctioned couldn't that also cause a spike?

That's a good thought, but I've owned several CJ pre's and have actually had 2 limiters that failed with no ill effects.

I think they are pretty much binary, meaning working properly or not working at all. I also don't believe it has the ability to trump the voltage regulator.