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Peavey VB-2 problem

walknbluez

walknbluez

Oct 3, 2007
1,017
8
Sacramento, CA
#1
I'm hoping BbbyBld sees this (his pm's are full right now). In the meantime, maybe someone else can help.

Long story short:

Amp went out. Had the internal faulty fuse issue repaired and new tubes installed.

Amp went out a second time. This time it was found that there was a short in the transformer. Peavey stepped up and sent my tech a new transformer, no questions asked. Tech installed it, tested everything, biased it (conservatively he said).

Amp went out a few nights ago. It was just the EXTERNAL slow blow fuse this time. BbbyBld said that it was probably weakened and on the verge from the prior problem and to just replace it with another 10 amp fuse. He said 7 amp would probably be enough but to use 10. Radio shack didn't have 10 so there's 7 in it right now.

Tonight: In the middle of playing several times there would suddenly just be silence, like it went dead, except all tubes and all lights lit. Then it will come back suddenly. A couple of times the outages lasted a good 15 seconds or so where I stopped playing and put the amp on standby, then back on and then nothing and then suddenly something. A couple of times it was just for a few seconds.....no sound, then back in. It didn't sound like a cable issue, although I will double check that. Not like any crackling in and out where you jiggle the cable near the input of your bass and you can tell, more like just a sudden out, then sudden back in.

Any ideas?
 
#2
Hi.

RoHs.

Seriously.

It's quite likely that You have a cold solder somewhere. PITA to find, especially from a tube amp that heats up pretty evenly anyway, so cold spray is next to useless.

If the head is still under warranty, I'd change the whole unit, not just swap parts and try to troubleshoot at Your expense.

Regards
Sam
 
#3
T-Bird said:
Hi.

RoHs.

Seriously.

It's quite likely that You have a cold solder somewhere. PITA to find, especially from a tube amp that heats up pretty evenly anyway, so cold spray is next to useless.

If the head is still under warranty, I'd change the whole unit, not just swap parts and try to troubleshoot at Your expense.

Regards
Sam
Click to expand...

I'm sorry, I don't understand what "RoHs" means. Can you explain?
 
#4
walknbluez said:
I'm sorry, I don't understand what "RoHs" means. Can you explain?
Click to expand...

http://en.wikipedia.org/wiki/Restriction_of_Hazardous_Substances_Directive

It's a hazardous substances directive from the European Union. One of the substances is lead. Solder used to be a lead/tin alloy. The new solder is lead free and does not form as good a solder joint as the old stuff unless conditions are perfect and the jury is still out on long term reliability.

If you know a plumber ask them which solder they prefer for soldering copper pipe, which is basically the same thing as electronics except on a larger scale.

mech
 
#5
Hi.

Thanks mech for the explanation.

I also apologise for not explainin it in the first place.

Wave soldering circuit boards with lead free solder is difficult, but perfectly doable, obviously ;). What makes it more complicated on amp PCBs, especially tube amp PCBs, is that the component leads differ greatly in diameter and therefore mass. Some of the older units are not fine-tuneable enough to give near 100% success rate.

Manufacturers test the PCBs thoroughly and sometimes a lemon slips through. That's the modern mass manufacturing and the regulations for you.

It is also entirely possible that the fault lies somewhere else as well. Warranty return is what I'd still suggest.

Regards
Sam
 
#6
walknbluez said:
I'm hoping BbbyBld sees this (his pm's are full right now). In the meantime, maybe someone else can help.

Long story short:

Amp went out. Had the internal faulty fuse issue repaired and new tubes installed.

Amp went out a second time. This time it was found that there was a short in the transformer. Peavey stepped up and sent my tech a new transformer, no questions asked. Tech installed it, tested everything, biased it (conservatively he said).

Amp went out a few nights ago. It was just the EXTERNAL slow blow fuse this time. BbbyBld said that it was probably weakened and on the verge from the prior problem and to just replace it with another 10 amp fuse. He said 7 amp would probably be enough but to use 10. Radio shack didn't have 10 so there's 7 in it right now.

Tonight: In the middle of playing several times there would suddenly just be silence, like it went dead, except all tubes and all lights lit. Then it will come back suddenly. A couple of times the outages lasted a good 15 seconds or so where I stopped playing and put the amp on standby, then back on and then nothing and then suddenly something. A couple of times it was just for a few seconds.....no sound, then back in. It didn't sound like a cable issue, although I will double check that. Not like any crackling in and out where you jiggle the cable near the input of your bass and you can tell, more like just a sudden out, then sudden back in.

Any ideas?
Click to expand...

If it's not a bad speaker cable there is a loose connection somewhere. The contact is breaking when the amp heats up and the parts inside expand.

In order of likely hood:

1. Loose wire connection. From description, either power or output transformer wire (the red ones).

2. Loose preamp tube socket contact.

3. Sprung effects loop jack switch (can be proven with jumper cable in FX loop).

4. Bad solder connection.

5. Bad standby switch.
 
#7
BbbyBld said:
If it's not a bad speaker cable there is a loose connection somewhere. The contact is breaking when the amp heats up and the parts inside expand.

In order of likely hood:

1. Loose wire connection. From description, either power or output transformer wire (the red ones).

2. Loose preamp tube socket contact.

3. Sprung effects loop jack switch (can be proven with jumper cable in FX loop).

4. Bad solder connection.

5. Bad standby switch.
Click to expand...

Hey Bobby,

#5 is interesting to me because my guitarist noticed that when the external fuse blew it happened right when I was turning the standby switch on or off (don't remember which but he said to me right after the fuse blew "I saw it go down right when flipped the standby switch".

Then again #1 is interesting because the power transformer was just replaced.

I'm going to give this list of possibilities to my tech who repaired and see what he says.
 
#9
Question to BbbyBld:

We've talked together about this amp before, killer tone by the way! Really getting a nice growly tone with it lately.

I'm having a bit of an issue when I turn the amp off of standby. Everything comes on normally but I hear a bit of noise in the signal. It's for no apparent reason, sometime it does this, and sometimes I don't notice any noise. Could this be a pre-amp tube taken a dump on me? Thanks in advance.

Sorry for hi-jacking the thread, but it pertains to the so same amp.
 
#10
I believe that this may in fact not be the amp but the speaker jack and before I go any further I'm going to investigate that further to confirm that. After the first repair of the amp, I was probably a little paranoid and so I automatically assumed it was the amp.
 
#11
dubstylee said:
Question to BbbyBld:

We've talked together about this amp before, killer tone by the way! Really getting a nice growly tone with it lately.

I'm having a bit of an issue when I turn the amp off of standby. Everything comes on normally but I hear a bit of noise in the signal. It's for no apparent reason, sometime it does this, and sometimes I don't notice any noise. Could this be a pre-amp tube taken a dump on me? Thanks in advance.

Sorry for hi-jacking the thread, but it pertains to the so same amp.
Click to expand...

When you take the amp off standby the power tube plates start to heat up and expand, which can cause audible noise to be amplified. Sometimes you will hear a few short bursts of white noise, sometimes you will hear a few pops here and there over the next 5 minutes, and sometimes you won't hear anything at all. It's nothing to be worried about unless it happens all the time. One of the best way to avoid thermal stress is to not use the standby like a mute/beer switch. Use it to stage the turn-on and leave it on.

Preamp tubes can make similar noises, but if they are bad it will happen all the time. They can make other noises too like groaning, cricket noises, oscillations, and most commonly becoming microphonic.
 
#12
Thanks Bobby! One more question:

Sometimes I notice that the amp will make a clicking noise from an actual mechanism inside of the amp, it does not come from the speakers. It sounds like a "dink", is that jus the tubes heating up?

Thanks
 
#14
dubstylee said:
Thanks Bobby! One more question:

Sometimes I notice that the amp will make a clicking noise from an actual mechanism inside of the amp, it does not come from the speakers. It sounds like a "dink", is that jus the tubes heating up?

Thanks
Click to expand...

You can hear some "tinking" from the power tubes as they heat up and cool down.

If you mean the clicking (kinda like a car turning signal) that happens when you activate/deactivate certain features, that's coming from the relays inside which control the signal paths.
 
#15
This right here is why Talkbass rocks! Direct questions being answered by an actual engineer of the product.

Also I love the VB-2 and have had none of these problems though I wish the channels were bendable the overdrive channel really eats the low end.
 
#16
Yup Bobby, that's what it sounds like. It sounds like it's the power tubes heating up and cooling down. That's what I figured it was. Also, I guess I should only use the standby switch when staging "power on". Should I also put it on standby before shutting down as well for a few minutes? Thanks!
 
#19
kuys said:
Also I love the VB-2 and have had none of these problems though I wish the channels were bendable the overdrive channel really eats the low end.
Click to expand...

I don't mean to derail the thread but it's here and this question isn't worth making a new one.

I haven't been able to play a VB-2 yet but I'm saving up for one (hopefully used), however I'm worried about the overdrive channel. Nobody has any demos of it and I remember someone saying that it "sounds cheesy". Is there something with a similar overdrive sound that it could be compared to? Is it more like a nifty little extra on a generally nice amp? There's no way in hell I'll be able to afford a VB-3 even if it has a "better" overdrive channel, so I'm really curious about this.
 

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