Peavey VB-2 repair

Discussion in 'Amps [BG]' started by Ajak, Dec 17, 2013.


  1. Ajak

    Ajak

    Joined:
    Mar 31, 2012
    Location:
    Bern, Switzerland
    Hello TB, sorry for the long post.

    I've had some bad luck with my Peavey VB-2. I got it in spring this year. It worked fine until it started giving me small electric shocks when I touched our mixer or a mic. Took it to a tech, the amp was fine, it turned out that somebody changed out the power strip in our rehearsal room, which apparently didn't have proper grounding. :confused:

    It then worked fine for like 2 rehearsals, when it just died away mid-song. Just no sound coming out. I tried both inputs with both channels, different basses, without pedals, anything I thought of.
    Then I found out that it works when I blug the bass in the fx return. connecting the send and the return with a patch cable didn't help though.
    So all I know is that the problem must be in the preamp section.

    So here are my options as I see it:

    1) Take it to a tech. Would be my favourite but the problem is, that this amp is pretty unhandy to carry and I don't drive. I did take it to a tech once and I thought: never again! On top of that the guy in the store told me that they will have to charge me around 100 bucks for just checking it. Without guarantee that they can fix it.

    2) Send it in on warranty. The problem with that is that I ordered it online from germany. The customer has to pay for international shipping, which will be pretty pricey with this amp.

    3) At least check the preamp tubes myself. I've never switched tubes but I'm pretty sure I can do it (there are plenty of instructing videos and posts I believe). The problem is that if I want to access the preamp tubes I'll have to take out some of the power tubes (the VB-2 is designed that way). And then I'd have to setup the bias again right? And I have no experience at all with that. And is it even possible that one of the preamp tubes is broken? Would the amp be dead silent or would there be some sort of noise?

    What would you guys do? Any advice will be appreciated. I just want my amp back! :bawl:
  2. VanillaThundah

    VanillaThundah VERY enthusiastic walks... Supporting Member

    Joined:
    Jul 30, 2010
    Media:
    1
    Location:
    Houston, TX
    If it's no sound and the amp was bought brand new, I am betting money that it's the infamous internal fuse that is known for going out on these amps.

    I had the same issue with mine, no problems in the least until it just stopped working one day when I was warming up. Amp wasn't even close to loud, then it just gave up and had no output no matter what. The place I took it to repaired it, but since I bought the amp used I had to pay out of pocket...it was only a little over $100 for me. If you have it registered under warranty, they may have a licensed tech in the area who can service it for you. Check Peavey's website, that should tell you where they are located.
  3. beans-on-toast

    beans-on-toast Supporting Member

    Joined:
    Aug 7, 2008
    Check all the fuses first.

    Swapping in new preamp tubes, one at a time, might save you a lot of trouble given your circumstances. If there is an issue with the amp that blew a preamp tube, it might blow the new one or the amp simply might not work. Then again it might resolve your issue. Sometimes tubes up and die.

    If you label the power tubes so that they go back into the same socket that they were originally in, you do not have to rebias them.
  4. JellinWellen

    JellinWellen

    Joined:
    Oct 18, 2012
    Location:
    Houston Tx
    If you send it to peavey, they WILL fix it. It's worth it IMO, these are very nice amplifiers.
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  6. B-string

    B-string Supporting Member

    Joined:
    Nov 21, 2008
    Location:
    Lake Havasu City, Az USA
    Switzerland to the US and back is going to be really expensive! :D

    Label the output tubes as BOT suggested and start swapping the small signal tubes. I don't have a schematic to know for sure but many amps use JFET opamps to buffer the effects loop like a TL072 which are inexpensive to replace if the tube swap fails.
  7. BbbyBld

    BbbyBld

    Joined:
    Oct 13, 2005
    Location:
    Meridian, MS
    Disclosures:
    MI Amp Engineer: Peavey Electronics
    This is most likely one of the two 12AX7's located towards the front of the amp. If you have to pull power tubes to get to them, you will not have to rebias. The preamp tubes can be a little difficult to grip for removal, but wearing a rubber glove will help big time. Buy a 12AX7 and try swapping.

    One thing you can do is check to see if your tuner output is still working. If it does not work, you know it's the tube that's closest to the input jack. If the tuner out does work, the other half of that tube could still be bad, but the tuner out not working would be a dead giveaway.

    The most important thing to remember when installing tubes like 12AX7's is to make sure the pins are straight, and make sure the pins are lined up correctly with the socket contacts as the tube is inserted so that you don't damage the sockets.
  8. seamonkey

    seamonkey

    Joined:
    Aug 6, 2004
    Techs seem out of reach for you, might as well learn some basic troubleshooting.
    First thing a tech will do, check the fuse, replace if blown and try it again.
    If it's not blown, or the replacement holds, they'll swap the tubes.
    Tubes are on sockets, They are swapped. People usually have a few spares.
  9. Ajak

    Ajak

    Joined:
    Mar 31, 2012
    Location:
    Bern, Switzerland
    Thanks so far guys! So I'll try the tuner output first (great idea!) then switch the tubes. If that doesn't help next thing to check are those JFET opamps. Is that something I can do or do I have to go to a tech at this point anyway?

    About the fuses: Could I even turn on the amp when the fuse is broken? Or are there seperate fuses for each section of the amp?

    Thanks again.

    Oh, btw: are you sure that there are 12AX7s in there? If yes I could drop by the store on my way to the next rehearsal.
  10. T-Bird

    T-Bird

    Joined:
    Apr 29, 2007
    Location:
    Finland (Northern Europe)
    Hi.

    +1 for swapping the pre-amp tubes as well as labeling the power tubes if You have to take them off.

    A little difficult is an understatement IME.

    As a favour to a friend, who "forgot" to tell there's two amps instead of one to be repaired, the other one being a Peavey ;), I have a Valve King 112 on the bench.

    Please, explain if You can, WHY THE HECK are the pre-amp tubes buried so deep???
    There's just the bald spot and the tip showing up from the sleeve.

    Makes:
    Pretty darn difficult for a novice if You aks me.

    Techs and more experienced tinkerers like me will be able to align the pins correctly, sure, but looks like a disaster waiting to happen when the tube rollin' starts.

    Regards
    Sam
  11. Ajak

    Ajak

    Joined:
    Mar 31, 2012
    Location:
    Bern, Switzerland
    What can go wrong while inserting the new tube if I remember the position the old tube was in and if I don't try to force it in? What exactly do you mean with "tube rolling" T-Bird?

    Oh and another question: I noticed there are a lot of different manufacturers that build 12AX7 tubes. Does it make a big difference? Is it necessary that both of the preamp tubes are exactly the same? I think I will take the old tubes out first to check the exact model and if possible buy the same. Or doesn't that even matter?
  12. T-Bird

    T-Bird

    Joined:
    Apr 29, 2007
    Location:
    Finland (Northern Europe)
    Hi.

    You may either bend a pin or a two, and/or crack the tube.


    :)
    You kind of answered your own question.
    Tube rolling is when you swap the tubes (to no end it sometimes seems) while searching for THAT tone.
    Quite addictive in fact.

    Some circuits react strongly to different tubes, other circuits are very insensitive.
    The designers choice.


    IME no.
    In "matched" pre amp tube sets only the measurements taken on one individual tubes triodes usually are within' certain specs.
    Useless marketing driven information as well IMO.

    Only the PI (phase inverter) could benefit from being "matched", but that's really not necessary either.
    The component tolerances render any inbalance null anyway.

    Always a good practise, but in this case they should be 12AX7's.

    Regards
    Sam
  13. Ajak

    Ajak

    Joined:
    Mar 31, 2012
    Location:
    Bern, Switzerland
    So the brand of tubes doesn't matter? Any 12AX7s' will do? (and won't sound completely different?)

    Thanks for the warning about tube rolling being addictive. I'll be careful. :)
  14. T-Bird

    T-Bird

    Joined:
    Apr 29, 2007
    Location:
    Finland (Northern Europe)
    Hi.

    IMLE with Peavey, their circuits are pretty insensitive to tube rolling, very typical with modern amps.
    Less headache for the manufacturer.

    With current production tubes the manufacturer in the cheaper end of the price spectrum IME doesn't matter much, completely different with vintage or NOS tubes.

    There's only a handful of CP manufacturers anyway, most tubes are "tested" and rebranded Russian or Chinese tubes.

    Regards
    Sam
  15. BbbyBld

    BbbyBld

    Joined:
    Oct 13, 2005
    Location:
    Meridian, MS
    Disclosures:
    MI Amp Engineer: Peavey Electronics
    There are none. B-string was speculating.

    There are different fuses for different sections of the amp, but since you're amp works by plugging into the FX return, none of your fuses are blown.

    They're just cold ;)

    You want a 12AX7 with low microphonics, which means that if the amp is physically vibrated, the tube innards are less likely to vibrate and create noise or feedback. The amp shipped with JJ ECC83S (European designator for 12AX7) tubes, which is arguably the best all around current production 12AX7 variant. Just use one of those and keep it simple.
  16. B-string

    B-string Supporting Member

    Joined:
    Nov 21, 2008
    Location:
    Lake Havasu City, Az USA
    Thanks for the info on the effects loop Bobby :)

    The tube sockets look something like this
    [​IMG]

    The tube something like this at the base where the pins are.
    [​IMG]

    Note the gap between the pins on the tube that is what you "line up" when inserting the tube in it's socket. Don't rely on the printed label position as they can vary widely.
  17. Ajak

    Ajak

    Joined:
    Mar 31, 2012
    Location:
    Bern, Switzerland
    Ok I got the tubes out an they are as BbbyBld said JJ ECC83S's. And there was another small tube in the middle close to the power tubes. It's a Ruby HG. What's that one for? I took it with me in case something's wrong with it. (EDIT: there was something like "12AN7 / ECCsomething" written near the socket of that other tube if that helps)
    Tomorrow I'll go to store and ask if they have some sort of a tube testing device (is there such a thing?). Shouldn't be as expensive as a whole amp check. Then if necessary order some of those tubes.

    Btw it was quite easy to get the preamp tubes out, but that HG was a real pain. I tried for more than 10min then a friend tried and managed to pull it out after like 2-3 more minutes. :eek:
    I also tried to put the preamp tubes back in and I quickly found the position they're supposed to be in, so installing new tubes won't be too difficult.

    So if there are no JFET opamps in the VB-2 is there anything else to check if it's not the tubes?

    Thanks a lot guys!
  18. BbbyBld

    BbbyBld

    Joined:
    Oct 13, 2005
    Location:
    Meridian, MS
    Disclosures:
    MI Amp Engineer: Peavey Electronics
    The one that's close to the power tubes is the phase splitter. It should be a 12AT7. It drives the power tubes. That one is good because your amp works through the return jack.

    Tube testers do exist. Some music stores might have a tube tester. Really, the best thing to do with questionable tubes is just try subbing them out because tube testers don't tell you everything. I'd be surprised if a music store wouldn't be able to sell you a 12AX7. Even if they don't have a JJ, they should have something. If you get some random 12AX7 and think the amp sounds weird, try swapping it to the other slot. Usually, you want your best tube in the first slot because any issues with the first tube in the chain get amplified through the whole amp.

    If it's anything else, a tech will have to look at it. A preamp tube is most likely.
  19. Ajak

    Ajak

    Joined:
    Mar 31, 2012
    Location:
    Bern, Switzerland
    The store had exactly the tubes I've had before and now the amp works perfectly! Thank you so much for your support. Saved me quite some money and time. Now I feel like I have to buy some gear with the money I saved. :D

    Really enjoyed playing it yesterday. After installing the tubes I just kept on jamming and jamming... :bassist: I just remebered why I've bought it in the first place.

    And I'm glad I can bring it to the gig on the 3rd of january. First gig with the band I'm using it with, I'm so happy I'll play through my VB-2!

    Thanks again!
  20. B-string

    B-string Supporting Member

    Joined:
    Nov 21, 2008
    Location:
    Lake Havasu City, Az USA
    Awesome! Send BbbyBld a virtual beer, he designed your amp and is always there to help an owner. :)

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