New Tubes? Help!!

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New Tubes? Help!!

Postby monroe » Tue Oct 28, 2008 8:43 am

I've got a Fender Princeton Reverb (either 1980 or 81, not sure which) amp, and I think I need some new tubes for it.

After playing for a short period, it starts making a nasty crackling sound. I can briefly get it to stop by reaching in and jiggling the offending tube (it's always the same one), but after awhile it'll just start doing it again.

So this morning I pulled the tube out to see what kind it was. I think the amp has the original tubes in there. This one is labeled as a 6V6GTA. It's Fender branded, and says "made in the USA", which leads me to believe that it's either an RCA or GE tube.

Anyway, I'm new to all this tubage, and it appears that 6V6GTA's are old and no longer made as far as I can tell? Is that right? If so, what should I get as a replacement? If not, where can I find some 6V6GTA's?
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Postby tigerstrat » Tue Oct 28, 2008 8:54 am

If that's the original power tube set then you've gotten a LOT of bang out of them at around 28 years!

You'll need to replace both 6V6's as a pair, AND get the bias balanced by a tech (one who will actually check it and adjust it, not just slap the tubes in and bill you $75 for labor like a certain one I used to work for).

Hmmmm 80-81... Is it a Princeton Reverb II? Black front panel? That would be the big brother to my '82 Super Champ.
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Postby jackr » Tue Oct 28, 2008 9:11 am

You can buy a full replacement kit from these guys.

http://www.eurotubes.com/

I have bought from them before and they know thier shit. Great tubes and pricing. If you are unsure of anything just ask them. I was clueless and they really were patient with me.

I dont know what it is like on your amp but mine is very easy to bias. You will have to bias it when you install your new tubes.
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Postby monroe » Tue Oct 28, 2008 9:11 am

Thanks for the info. It's definately not a II. It could even be a 79 or 78. It's actually not mine. It belongs to my father-in-law, but he was gracious enough to let me use it "for the forseeable future", as it was just sitting in his closet not being used.
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Postby tigerstrat » Tue Oct 28, 2008 9:23 am

monroe wrote:Thanks for the info. It's definately not a II. It could even be a 79 or 78. It's actually not mine. It belongs to my father-in-law, but he was gracious enough to let me use it "for the forseeable future", as it was just sitting in his closet not being used.


If it was sitting unused for many years, it may very well need a full cap job... before it develops REAL problems.
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Postby waldo041 » Wed Oct 29, 2008 6:30 am

tigerstrat wrote:
monroe wrote:Thanks for the info. It's definately not a II. It could even be a 79 or 78. It's actually not mine. It belongs to my father-in-law, but he was gracious enough to let me use it "for the forseeable future", as it was just sitting in his closet not being used.


If it was sitting unused for many years, it may very well need a full cap job... before it develops REAL problems.


i would change the electrolytic capacitors, the other caps will keep the mojo of the amp and changing them could affect the sound. they also a have a much longer shelf life. electrolytics have a shelf life around 10 years and the older they get the more unstable they will become. so i would assume that when tigerstrat mentions a full cap job he is really referring to the electrolytics.

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Re: New Tubes? Help!!

Postby jonarobb » Wed Oct 29, 2008 6:57 am

monroe wrote:I've got a Fender Princeton Reverb (either 1980 or 81, not sure which) amp, and I think I need some new tubes for it.

After playing for a short period, it starts making a nasty crackling sound. I can briefly get it to stop by reaching in and jiggling the offending tube (it's always the same one), but after awhile it'll just start doing it again.

So this morning I pulled the tube out to see what kind it was. I think the amp has the original tubes in there. This one is labeled as a 6V6GTA. It's Fender branded, and says "made in the USA", which leads me to believe that it's either an RCA or GE tube.

Anyway, I'm new to all this tubage, and it appears that 6V6GTA's are old and no longer made as far as I can tell? Is that right? If so, what should I get as a replacement? If not, where can I find some 6V6GTA's?


If it has the original GE 6V6GTA's w/o the base, they will most likely outlive the amp.

With that said, if the crackling stops when you're wiggling or gently rocking one of the 6V6GTA's back and forth then the sockets likely need to be cleaned and retensioned.

Additionally if the offending crackling stops or starts with any moving of the 6V6GTA's only, you should check the cathode to ground wire on that tube socket, Pin 8. Those late 70's Fender were put together by blind Mexican grandmothers and as such the cathode to ground solder joints are suspect 75% of the time.

As far as a cap job, those Mallory cap cans in the PR's are pretty forgiving. If it ain't hummin' don't bother.
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Postby RiverRat » Wed Oct 29, 2008 7:07 am

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Last edited by RiverRat on Tue Feb 22, 2011 10:39 am, edited 1 time in total.
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Postby jck_strw » Wed Oct 29, 2008 8:34 am

Whoops. I thought this was a thread asking for ISP recommendations. :)
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Postby Dozin » Wed Oct 29, 2008 8:35 am

Is there instructions online that show the procedures how to bias a amp? My buddy is a electrical engineer I just want to send him a link.
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Postby tigerstrat » Wed Oct 29, 2008 8:46 am

waldo041 wrote:so i would assume that when tigerstrat mentions a full cap job he is really referring to the electrolytics.


Yep that was what I meant. Me and my sloppy lektroniks again. Thanks for clarifying the butter!
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Postby tigerstrat » Wed Oct 29, 2008 8:51 am

Dozin wrote:Is there instructions online that show the procedures how to bias a amp? My buddy is a electrical engineer I just want to send him a link.


There are several. Here's one from Lord Valve: http://www.duncanamps.com/technical/lvbias.html
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Postby Dozin » Wed Oct 29, 2008 9:06 am

tigerstrat wrote:
Dozin wrote:Is there instructions online that show the procedures how to bias a amp? My buddy is a electrical engineer I just want to send him a link.


There are several. Here's one from Lord Valve: http://www.duncanamps.com/technical/lvbias.html


Thanks Tom
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