Peavey VB-2 question (went out)

walknbluez · #1 01-27-2011, 11:47 PM

I've had my Peavey VB-2 repaired twice. First time it was the internal fuse and was covered by an extended warranty. Second time it was a short in the power transformer. It was out of warranty but Peavey sent one to the tech on the house. Tech dialed everything in and I've been using it for months on end with no problems. He also installed a fuse holder for the internal F2 fuse for easy future replacement if needed.

Last night, everything was plugged in and I took it off standby. My bandmate was turning some things on the board to dial in his vocals. At the same time, I heard a couple of snap, crackle, pops and saw my speaker cone move. He looked at me and said "this is on a completely different circuit" which appeared to be true. I was plugged into one outlet in his garage on one side and he was on the other side.

Anyway, now no sound. Tubes are all lit up. I replaced the fuse in the back but no luck. Normally there is a bit of noise when moving the standby switch from off to on. Now not a bit of noise from that either.

The amp is no longer under warranty. I will probably end up bringing it to a tech but first was going to try and replace the internal fuse that no longer has to be soldered (since it now has a fuse holder). But I have no idea where it is located. Anyone know where it is located? Or is it unlikely that it is the internal fuse again since it is not one of the old faulty fuses?

jastacey · #2 01-28-2011, 08:08 AM

If the tech used the same location, it is in the upper right corner, when the amp is flipped over, those fuses are about 3/4" long

craig.p · #3 01-28-2011, 08:13 AM

That amp needs bench time, not a fuse replacement. If the fuse is blown, it's a symptom of a much deeper problem. You might want to bite the bullet and send the thing back to Peavey so they can apply any and all circuit updates that will prevent this sort of thing from happening again.

BbbyBld · #4 01-28-2011, 08:29 AM

Sounds like you had a power tube arc out. What power tubes are you using?

walknbluez · #5 01-28-2011, 01:40 PM

Quote:

Originally Posted by craig.p

That amp needs bench time, not a fuse replacement. If the fuse is blown, it's a symptom of a much deeper problem. You might want to bite the bullet and send the thing back to Peavey so they can apply any and all circuit updates that will prevent this sort of thing from happening again.

Oh, it's had plenty of bench time. When the transformer was replaced, the tech checked all the circuitry and everything and it was fine.

walknbluez · #6 01-28-2011, 01:41 PM

Quote:

Originally Posted by BbbyBld

Sounds like you had a power tube arc out. What power tubes are you using?

Hi Bobby,

The tubes are Ruby EL34BHT's

So what does it mean when a power tube arcs out and what does that mean in terms of what has to be done to repair the amp?

jastacey · #7 01-28-2011, 06:07 PM

The Fuse protected the amps transformers ...need to find which tube/tubes failed and replace them along with the High Voltage fuse ... IMHO

walknbluez · #8 01-29-2011, 04:26 PM

Quote:

Originally Posted by jastacey

The Fuse protected the amps transformers ...need to find which tube/tubes failed and replace them along with the High Voltage fuse ... IMHO

Is that something I can learn to do or does it require a tech. I was under the impression that if one tube went out you had to replace all of them. Also wouldn't it require re-biasing?

jastacey · #9 01-30-2011, 08:23 AM

I all depends on how comfortable you feel on working on your amp, I think it's not that hard, but you'll need a tube tester, sometimes when a tube shorts out, you can see slight blacking on the innards, but most of the time it looks normal, the bias will not need to be changed if you use the same brand of tubes, provided they are matched closely to the existing ones .... I too, have this same amp, but it's still loaded with the JJ-EL34's ... how did it sound with those Chinese tubes? ... another question ... how long were those tubes in use?

walknbluez · #10 01-30-2011, 01:19 PM

Quote:

Originally Posted by jastacey

I all depends on how comfortable you feel on working on your amp, I think it's not that hard, but you'll need a tube tester, sometimes when a tube shorts out, you can see slight blacking on the innards, but most of the time it looks normal, the bias will not need to be changed if you use the same brand of tubes, provided they are matched closely to the existing ones .... I too, have this same amp, but it's still loaded with the JJ-EL34's ... how did it sound with those Chinese tubes? ... another question ... how long were those tubes in use?

I thought it sounded great with those tubes. When the internal fuse went out the first time, the tubes had to be replaced and Bobby suggested the Ruby's. They have been in there since October of 2009 with usage of about twice per week.

walknbluez · #11 01-30-2011, 06:26 PM

Quote:

Originally Posted by jastacey

I all depends on how comfortable you feel on working on your amp, I think it's not that hard, but you'll need a tube tester, sometimes when a tube shorts out, you can see slight blacking on the innards, but most of the time it looks normal, the bias will not need to be changed if you use the same brand of tubes, provided they are matched closely to the existing ones .... I too, have this same amp, but it's still loaded with the JJ-EL34's ... how did it sound with those Chinese tubes? ... another question ... how long were those tubes in use?

So where do I get a tube tester?

walknbluez · #12 01-30-2011, 11:48 PM

Quote:

Originally Posted by jastacey

If the tech used the same location, it is in the upper right corner, when the amp is flipped over, those fuses are about 3/4" long

I'm not seeing this. Is this fuse accessible by removing the back grill or are you talking about it being in the upper right corner after removing some other portion?

jastacey · #13 01-31-2011, 07:57 AM

The fuse that protects the high voltage feed to the tubes , is inside the amp, you have to remove the amp chassis from the amp case, ( remove the mesh grills, the wood screws along the back edge, the 5 screw bolts on the bottom, and slide the amp out, the tolex might hang-up the transformer support bracket ) then slide the chasis out and flip the amp over, look in the upper right hand top corner and you'll see 2 little fuses, if you tech reworked the high voltage fuse, it might be anything, but the original was soldered in, he might have put clips in, or used a inline fuse holder... I just don't know, make sure you know how to drain the filter caps so you don't shock the s**t out of yourself, when your poking around inside the amp

As to tube testers, E-Bay would be the first place, but I strongly urge you to go to this link, http://tubesound.com/ and read the tube testers and tube equipment section, so you know what your getting into

You might want to try a different tube ( EH-6CA7, JJ-6CA7, Winged "C" EL-34 ) I personally have never had good luck with Chinese tubes.... might be cheaper to have a tech/shop do the work, but you'll have to wait for the amp

RCCollins · #14 01-31-2011, 07:58 AM

please don't electrocute yourself

walknbluez · #15 01-31-2011, 01:06 PM

Quote:

Originally Posted by RCCollins

please don't electrocute yourself

After reading what jastacey wrote, I'm not even going to attempt repair myself.

walknbluez · #16 02-14-2011, 12:48 AM

Well I put a new internal fuse in and turned it on and it works. It sounds like what Bobby said was the case, a tube arcing. One thing though, now I'm getting some slight noise coming through the speaker even when the mute button is on. Sort of like a very, very low buzz and only when the master volume is in a certain position. 0 - 3 barely any noise, 4 - 6 slight buzz, 7 - 9 slight buzz but louder, and then when on 10 barely any noise again. Then when I plugged my P bass in and took it off standby and the volume full on the bass, I got a hum that varied as moved around. This is with the amp outside of the case. I don't recall this before the fuse blowing. Any ideas?

BbbyBld · #17 02-14-2011, 08:32 AM

Quote:

Well I put a new internal fuse in and turned it on and it works. It sounds like what Bobby said was the case, a tube arcing. One thing though, now I'm getting some slight noise coming through the speaker even when the mute button is on. Sort of like a very, very low buzz and only when the master volume is in a certain position. 0 - 3 barely any noise, 4 - 6 slight buzz, 7 - 9 slight buzz but louder, and then when on 10 barely any noise again. Then when I plugged my P bass in and took it off standby and the volume full on the bass, I got a hum that varied as moved around. This is with the amp outside of the case. I don't recall this before the fuse blowing. Any ideas?

The master volume is in close proximity to the power transformer. When you turn the pot, you are moving the wiper of the pot through the hum field of the transformer. As you noticed, it's worse around 7-9. That's where the wiper is closest to the transformer.

It's going to hum a little more outside the cabinet. The cabinet is coated with graphite paint and is grounded to the chassis when everything is put together.

walknbluez · #18 02-14-2011, 11:03 PM

After putting the amp back into the chassis, I flipped it on an immediately had a tube arc out again (blue flash) and blow the fuse again. So from what I understand, this means that one of the tubes is faulty (a short?), is that correct? And that I can get one tube to match the set without having to replace all of them (it has six tubes) by ordering one with a matching number on the base. If so, how do I identify the tube that is arcing (since it isn't blown, a tube tester wouldn't determine this I presume)?

BbbyBld · #19 02-15-2011, 08:01 AM

Quote:

After putting the amp back into the chassis, I flipped it on an immediately had a tube arc out again (blue flash) and blow the fuse again. So from what I understand, this means that one of the tubes is faulty (a short?), is that correct? And that I can get one tube to match the set without having to replace all of them (it has six tubes) by ordering one with a matching number on the base. If so, how do I identify the tube that is arcing (since it isn't blown, a tube tester wouldn't determine this I presume)?

That's good! Now you are getting somewhere.

A tube tester won't really tell you anything.

The easiest thing to do is replace all the tubes at once and then keep your current set as replacements, but that gets expensive, and then you will still have a bad egg.

Replace the fuse and run the tubes in pairs only to identify the bad one. In other words, pull the B and C pair and test A only. Then go through B and C. One of those pairs will arc out again. Mark the bad pair, split it up and test the suspect tubes with known good ones in pairs.

Set the amp on the 2 ohm setting when playing with only one pair for this test.

The pairs are like this: AA/BB/CC

walknbluez · #20 03-06-2011, 10:30 PM

Quote:

Originally Posted by BbbyBld

That's good! Now you are getting somewhere.

A tube tester won't really tell you anything.

The easiest thing to do is replace all the tubes at once and then keep your current set as replacements, but that gets expensive, and then you will still have a bad egg.

Replace the fuse and run the tubes in pairs only to identify the bad one. In other words, pull the B and C pair and test A only. Then go through B and C. One of those pairs will arc out again. Mark the bad pair, split it up and test the suspect tubes with known good ones in pairs.

Set the amp on the 2 ohm setting when playing with only one pair for this test.

The pairs are like this: AA/BB/CC

I did what you said and tested in pairs but of course then each time none of the tubes arc'd out (and I turned it on and off several times each). I then used it at a jam for about 4 hours and it made it through without any problems. Is it possible that it was just a fluke thing?