Peavey VB2 - switching preamp tubes

tolson36 · #1 02-02-2010, 07:54 PM

Hi

I have a VB-2 that needs a preamp tube (ringing). I was wondering what the best way would be to get at them.

The front screen is screwed from the inside and one of the screws is blocked by a transformer.

If I simply do it from the rear I need to remove tubes and attempt to unscrew stubborn preamp socket cover screws (with little leverage) while reaching around a transformer.

Has anyone pulled the chassis? If so, was it as simple as removing the 4 screws at the bottom, the 2 big bottom bolts, and the screws along the back side?

Any problem threading the bottom screws and bolts back into the chassis?

Thanks in advance for any guidance.

PS--also, as long as I'm not opening the chassis, is there any shock risk from touching the 2 big transformers? And lastly, any problems with my strategy of leaving the screw (one that attaches screen from the inside) that's blocked by the transformer off. I'm afraid it could rattle but would like a way to enter from the front easier.

jastacey · #2 02-02-2010, 09:46 PM

I'd just pull the back screen/cover off, mark the power tubes, as to there position, push down on both sides of the spring holders, and wiggle/pull the tubes out by the bases, then when you get to the 2 front preamp tubes, push slightly down on the shield covers and twist to unlock them, wiggle/pull the tubes out, the preamp tubes pin set is oriented with the large space between the pins facing the front of the amp .. there is no need to pull the chassis ...but if you want to you can ...and no ,it is not problematic in getting the bolts back in

tolson36 · #3 02-03-2010, 12:39 AM

thanks

I tried to do as you indicated but the aluminum shield covers of the front two tubes go over an aluminum base piece. Not enough of the tube sticks out above the base to wiggle the tubes out. So I need to unscrew two small black screws on the bases to remove the bases. Problem is--the screws are in so tight--and the angle is so bad--that I can't get the screws out.

I'm going to pull the chassis as the only way to get to those screws and get them out.

So I assume you've had the chassis out and didn't have a problem rethreading, etc

bassninja7 · #4 02-03-2010, 02:55 AM

it was a bitch to get it out... but thats how i had to replace the preamp tubes :/

XtraLongScale · #5 02-03-2010, 04:05 AM

This is from my last tube rolling excursion from the previous summer. It is a pain to remove but more than anything else it's just time consuming - even with a cordless drill so it's not very often I pull the chassis out but it did make for relatively quick tube changing in V1 & V2 and the sight of those huge transformers is glorious

carbonfold · #6 02-03-2010, 07:09 AM

You can leave the amp in the chassis. Just pull all your power tubes out first, then you can get to the preamp tubes without a prob.

BbbyBld · #7 02-03-2010, 07:23 AM

As was said, you can replace the preamp tubes without removing the chassis.

Carefully pull out some of the power tubes so you can reach your arm in. You can use a rubber-coated work glove or even a latex glove to help grip the preamp tubes to pull them out so you don't have to remove the shield bases.

jastacey · #8 02-03-2010, 08:12 AM

Did changing out the tube fix your problem? ...

tolson36 · #9 02-03-2010, 11:14 AM

Thanks for the ideas (especially the one on the rubber gloves).

I have not changed it yet. However, I'm not positive it's the preamp tubes. The ring is on a single note or two and it's not extremely loud.

I have been able to tap on the tubes and heard nothing at all.

I think it's possible it's some sympathetic ringing of some metal parts either in the amp or the speaker cab. I tried it with a second cab and did not hear it.

ZanaZulu807 · #10 04-08-2012, 12:16 PM

In recognition of Easter, I'm resurrecting this dead thread!...

I was thinking about changing out the preamp tubes in one of my VB-2's as well as I'm getting a chorus/reverb like noise in the OD channel. I was told that it was likely the preamp tubes going, I'm not so sure about that.... However, I was thinking anyway of doing this about a month ago to see if it could add any change or shape to the OD channel. From what I can see, there is a Electro-Harmonix 12AT7 tube and I can't make out the 12AX7, only it has red shading. Has anyone tried changing out the preamp tubes to see if there's any difference in the channels on the amp? Or is there not much difference at all?

BbbyBld · #11 04-08-2012, 04:20 PM

You can get a weird swirly hum noise if you use a solo single coil pickup. I have one bass that does that with the vb.

Try one of those hybrid preamp tubes in the number one slot. You can get tubes where one half is a 12 ax and one half is a 12at.

ZanaZulu807 · #12 04-08-2012, 07:10 PM

It could be a single coil issue... I was using a Jazz with the active pickups and the signal sounded a bit hotter than usual, but I plugged into the Low Gain input as opposed to the High Gain which should've at least tamed it a bit. I'll check out that hybrid preamp option, but I had my eyes set on some JJ's to replace the ECC81 and 83.

Buildthebombs · #13 03-18-2013, 07:03 PM

I have a peavey vb-2 bass amp and it makes a weird.buzzing noise... is anyone else having the same problem? I'm using a VB 810 speaker cabinet along with the amp both are brand new if anybody knows how to fix this please let me know
Its driving insane!

xuztujma · #14 03-18-2013, 07:30 PM

You can leave the amp in the chassis.