Dead preamp tube?

This forum is for talking about all kinds of Peavey guitar amplifiers.
User avatar
Posts: 17
Joined: Fri Oct 14, 2011 6:55 pm
Location: Montreal, Quebec, Canada

Dead preamp tube?

Postby nlaplante » Sat Oct 15, 2011 9:26 am

Hi everyone,

I recently put a Tung-Sol 12AX7 in the V1 position of my JSX head. Everything was ok until I decided to test the outcome of putting it in various positions.

When I tried to remove the tube from V1, it was very difficult. The tube was stuck in there. I finally managed to get it out and put it in V2.

Powered up the amp, and I was getting no sound at all. I switched it to V3 (which is the fx loop and active eq I think) and I was getting sound. But as soon as I engaged the FX loop, the sound was gone.

Do I have a faulty tube? I see its filament light up a bit but not as much as my other preamp tubes.
Be someone

User avatar
Posts: 1875
Joined: Fri Jul 24, 2009 5:38 pm
Location: Columbia, Tennessee

Re: Dead preamp tube?

Postby thunda » Sat Oct 15, 2011 10:35 am

that tube has a spiral filament encased in the plate structure, it won't glow as brightly as other tubes. That being said, there is a problem with Russian made spiral filament tubes when used in cathode follower positions. V1 is not a cathode follower. But I am unsure of the other positions in your amp. Many times, particularly with Mesa amps, the tube will fail almost immediately when placed in a cathode follower position (as in V4 in my Heartbreaker, for example).

Hope this helps.
When Gibsons are outlawed, only outlaws will have Gibsons

Si Gibsons proscriptae soli proscript habebit Gibsons

(heart) le Peavey
Posts: 433
Joined: Sat Apr 17, 2010 2:54 am

Re: Dead preamp tube?

Postby (heart) le Peavey » Sat Oct 15, 2011 11:45 am

If V1 was the last position that worked, have you tried it there again?

User avatar
Van Noord
Posts: 520
Joined: Wed Dec 03, 2008 10:44 am

Re: Dead preamp tube?

Postby Van Noord » Sat Oct 15, 2011 10:52 pm

I would try it in V1 again and see the result.
I believe V3 is the Cathode Follower stage in the JSX (maybe Enzo can confirm). One time I put a Sovtek LPS in the V3 spot of my JSX and the tube failed almost immediately.

I didn't care for the Tungsol 12AX7 in V1 of my JSX. It was too bright and a little noisy.
The absolute best I've found to use are JJ ECC83S's in V1,V2,&V3 and a Russian tube in V4, either a Sovtek or EH.


Posts: 30118
Joined: Fri Sep 12, 2008 3:10 pm
Location: The Mountain Retreat [Cincinnati Ohio]

Re: Dead preamp tube?

Postby Classic30inCincy » Sun Oct 16, 2011 8:23 am

Tubes can & will fail.......

IF you purchased tube new request exchange.

Tube manufacturers generally provide 60 day warranty.

PAF Classic Series Tube Kit.......Created By Classic30inCincy
Majic Mojo Tradename..........Created By Classic30inCincy
Graduate Of Joe Friday / Dragnet School Of Correspondence
Doctorate Degree Diplomacy From Royal Order Possum Lodge

User avatar
Posts: 7953
Joined: Fri Sep 12, 2008 10:24 pm
Location: Lansing, Michigan

Re: Dead preamp tube?

Postby Enzo » Mon Oct 17, 2011 6:02 pm

There is no cathode follower in the JSX. The only stage with a cathode at any voltage to speak of would be the phase inverter, and that shouldn't be near enough to trouble any 12AX7 model.

The tube was probably damaged. Try a different tube, grab one out of another amp if you need to.

Return to “Guitar Amplifiers”

Who is online

Users browsing this forum: No registered users and 31 guests