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tube head - no sound/ideas?

andysvec

andysvec

Aug 15, 2004
1,104
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was Guam, now Vegas!
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#1
Have a Peavey VB-2 head that powers up, all tubes lit, power light on in the front, etc, but no sound coming out. I tried different speaker cables, different speaker out jack, different cabs, wiggling standby switch, etc, still not any sound at all coming out. I also tried a new 10A/250V fuse in the back but same thing. Any other ideas I could try? Was working fine one night, no sound the next, can't figure it out.
thanks - Andy
 
#6
If you place your ear up by the speaker is it dead quiet? No matter what is going on with the amp if the power amp is powered up it will make some small noise even with a mute. If you hear NOTHING I suspect you dont have B+ on the plates of the finals. There might be a couple resistors that let go. The other option is the output transformer. Or directly the power supply itself. If you have filaments, the next step would be voltage, but thats danger zone if your not up on trouble shooting. If you have slight hiss, then work your way forward in the amp. Also note a 12AX7 is a dual triode, they have two filaments in them, both sides need to light up. BOB
 
#7
thanks everyone, good info. In reply:

Is there a mute switch?
yeah, I tried jiggling/switching/etc.

Did you try different basses and/or instrument cables?
yes, tried another bass and just tried another inst cable, same.

Was the volume turned up on your bass?
yes

The impedance selector on the back isn't between settings is it?
good one, checked it and it is correct.

Did you try jumpering the effects loop?
didn't try this yet, will be my next step.

stumbo, thanks for that tip too, sounds like my prob - I'll try to get in touch with him.

thanks again everyone.
 
#8
Hmmm. Let's see. :confused: It says here that it's completely ruined and you should sell it to me for $50.

Seriously, I couldn't find a schematic, but I'd kinda recommend that you don't go poking around inside, unless it's been unplugged for a while, seeing as how tube amps can run several hundred volts inside.

If you do decide to have it fixed instead of selling it to me ($55?), it's probably a relatively easy fix. There may be some fuses inside that aren't immediately visible that should be checked as well.

($60?)
 
#9
Caca de Kick said:
You say tubes are lit.
You can easily probably see the power tubes, but can you see that the preamp tubes are lit too?
Click to expand...

good call, just did a little more troubleshooting, I see that all power amps are lit/both 12ax7s are lit/but the one 12at7 in the middle is not lit. I have two other brand new 12at7s and tried both of them, neither light. could be the problem...
 
#10
andysvec said:
Have a Peavey VB-2 head that powers up, all tubes lit, power light on in the front, etc, but no sound coming out. I tried different speaker cables, different speaker out jack, different cabs, wiggling standby switch, etc, still not any sound at all coming out. I also tried a new 10A/250V fuse in the back but same thing. Any other ideas I could try? Was working fine one night, no sound the next, can't figure it out.
thanks - Andy
Click to expand...

There was a run of these amps with a fuse issue. The symptoms were the same as those you are experiencing. Call Peavey Tech Support -- they should be able to resolve this.

- Greg
 
#13
andysvec said:
good call, just did a little more troubleshooting, I see that all power amps are lit/both 12ax7s are lit/but the one 12at7 in the middle is not lit. I have two other brand new 12at7s and tried both of them, neither light. could be the problem...
Click to expand...

That is really odd. Would not be a fuse problem since then none of the tubes would light. If ANY tube in the 12AT7 doesn't light then I would say there is a problem with the filament connections to that tube (cold solder joint, broken PCB trace, etc.). Sounds like a warranty claim to me.
 
#14
gerryjazzman said:
That is really odd. Would not be a fuse problem since then none of the tubes would light. If ANY tube in the 12AT7 doesn't light then I would say there is a problem with the filament connections to that tube (cold solder joint, broken PCB trace, etc.). Sounds like a warranty claim to me.
Click to expand...

The odds are that the 12AT7 is fine and the OP simply can't see the filament glowing. Tube "glow" rarely means anything other than how visible the filament may be. Several VB-2 users have experienced this problem due to a faulty fuse on the high voltage supply and Peavey has acknowledged it and will repair it under warranty.
 
#16
Yeah like I said, missing B+ on the power tubes. I didnt know this bugger had an internal B+ power amp fuse. Amps like the SVT AMPEG use 10 OHM resistors in the plate lead to act like a fuse incase of a tube short. When one of those suckers blow you get a big puff of smoke and flame saying hey sucker your amp is broke. Its a nice indicator telling you which tube shorted too. BOB
 
#17
rbonner said:
. Amps like the SVT AMPEG use 10 OHM resistors in the plate lead to act like a fuse incase of a tube short. When one of those suckers blow you get a big puff of smoke and flame saying hey sucker your amp is broke. Its a nice indicator telling you which tube shorted too. BOB
Click to expand...

The 10ohm/5 watt plate load is NOT the "fuse;" the 22 ohm/1 watt screen resistor goes much sooner. ;)
 

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