#1
Ok so I was playing my Peavey 3120 today and after a couple min of playing, it made a loud pop. As soon as that happened I looked and the powertubes were redplating. I immediatly turned it off. Ive pulled the fuse but can't tell if its blown or not. My mind automatically assumes the worst so what are the chances of a blown PT or something. If its just the power tubes then that not a huge deal as I was planning on getting some KT77s anyway. I bought the amp around a month ago used from guitarcenter.com. Ive never had any issues with anything Ive bought from them. Ive always matched the ohms on my cab and let it warm up properly before turning it on.

Please help me diagnose my amp. There aren't any good techs around here at all but Im less than two hours from Nashville if its a big problem.
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent
#2
seems like the tubes are goners. look really carefully at the fuse.
Jumping on dat gear sig train.
PRS Hollowbody II / BKP Warpigs
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Blackstar ID:Core Beam
#3
I can't see in the fuse at all. Its a blueish green on the outside. Its a bussmann 250v 10A fuse if that help at all. Im really hoping its just the powertubes cause I was planning on replacing them very soon anyway.
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent
#4
If they suddenly started redplating and you heard a pop you may have blown a bias resistor and not a fuse (I don't know what biasing system those amps use). Somebody needs to take a look inside. To check the fuse you'll have to test it with a multimeter. However if the mains fuse blew it wouldn't turn on at all so that wouldn't be the problem.
If you can't even test a fuse then you need to take it to a tech. Don't go poking around inside the amp if you don't know what you are doing.
Gilchrist custom
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Telecasters
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Cathbard Amplification
My band
#5
I know a bit, but not enough to poke around much. My multimeter broke so im SOL on that one. What would cause a bias resister to blow? I don't want to just stick another fuse in I really want to narrow down the problem. Also, like I said, no techs or anything around here. I do live less than 2 hours from Craig of CEC so maybe he would be willing to help out. I don't know when Im going to have the money for this though. I guess Ill shoot Craig an email to see if he has the time and get some sort of estimate. I was really hoping it would just be power tubes.......
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent
#6
You know, I didn't even realise it was you I was talking to - haven't had my second cup of coffee yet. Resistors will just blow for no reason, nothing lasts forever, it does happen. It could be power tubes but what popped? Was it a pop through the speakers or something internal? It could be your power valves but I'd want to look inside if it was my amp. It sounds a little suspicious.
If you can get Craig to take a squiz at it that sounds like a mighty fine plan.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#7
Well the pop came through the speakers. Later on I powered the amp on for five seconds to see if there was still redplating so I could make sure I was giving correct info but the power tubes were glowing blue which hadn't happened before. I would hate to bother Craig though unless I can't figure it out pretty soon though cause I know he probably has shit going on tryin to get the Brigand up (which by the way I might get to play some prototypes). Anyway, yeah the pop was from the speakers if that helps. The power tubes then started to redplate (they weren't before the loud pop). I instantly turned it off. It sounded amazing before the pop as well, there was no indication at all that something bad was about to happen.

I mean, I haven't had it that long so that sucks. I know shit goes wrong but it sucks. Called guitarcenter too and basically they are just blaming me. The dude tried to tell me that I didn't have a speaker load. ****ing assholes. Anyway how much does repair usually cost for something like this? I mean, I know how to remove the chassis and everything but don't think I would know if something was wrong inside. Also there wasn't any kind of burning or anything like that if thats important.
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent
#9
do your tubes still have the getters?
Jumping on dat gear sig train.
PRS Hollowbody II / BKP Warpigs
Strandberg OS6T / BKP Aftermath
Strandberg OS7 / Lace Poopsticks
Skervesen Raptor 7FF / BKP Warpigs
Skervesen Raptor 6 NTB / BKP Juggernauts
Hapas Sludge 7 FF / Hapas Leviathan
Anderson Baritom / Motorcity Nuke BKP Sinner Anderson H2+
Warmoth Baritone / BKP Piledriver
Ibanez Rg2120x / BKP Nailbomb

Blackstar ID:Core Beam
#10
Quote by AcousticMirror
do your tubes still have the getters?


getters?
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent
#11
Any other suggestions/help at all?
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent
#12
I agree with Cath. It sounds like something in your bias supply has opened up, and your grids are now at 0 reference (instead of negative, like they should be) and that is what is causing your valves to overdissipate.

I seem to remember reading somewhere that some Peavey amps have a fused bias supply. Not really a good idea.

I would open the amp and look for fuses mounted on the PCB's, and see if any of them are blown.

BTW, I think Min is referring to the Getter FLASH, which is the silver reflective portion usually near the tops of valves. If you have one that has turned from silver to milky white or light blue/gray, it means the valve has lost vacuum.

Also, you said that fuse is rated at 10 amps. That is WAY WAY WAY too high of a rating for most guitar amps, regardless of whether its the mains fuse or the HT. I've only ever seen the max mains fuse spec for 4 Amps.

This concerns me because manufacturers spec fuses at a certain rating for a reason. The fuses is there to blow when current conditions breach its rating. If the fuse is rated too high, whatever is causing the overcurrent condition will likely cause serious damage to other parts of the amp (such as transformers) before the fuse finally blows. That's why I ALWAYS check the fuses on a customer's amp when they bring it to me for the first time. I routinely see 4 and 5 amp fuses in 1 and 2 amp slots, or even 500mA slots.
Tastes like chicken, if chicken was a candy.
Last edited by ConfederateAxe at Mar 17, 2011,
#13
So whomever owned this amp before could have put in the wrong ****ing fuse? That sucks. Ill try to find some info on whats supposed to be in there. So you think I should remove the chassis and look for fuses on the pcb to see if they are blown? Ill do it tomorrow and see. If a fuse inside blew is that the problem or did the problem cause the fuse to blow? Also, if I can't get this sorted out by checking those fuses, Ill probably bite the bullet when I get some money and take it out to Craig.
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent
#14
Searched on google and found this: http://homerecording.com/bbs/equipment-forums/guitars-basses/tube-head-blown-fuse-why-320262/

seems like mine isn't the only one thats had this problem. Is the 3120 the new Bugera or something?

Edit: sorry for the double post, I wasn't payin attention
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent
#15
Fuses are very rarely the source of the problem, and rather simply an indicator that there exists a problem. Fuses blow due to overcurrent conditions in the path they are placed. Fuses CAN wear out over time, but it's not something that happens to consistently it can be quantified.

The unfortunate part of this is that there doesn't seem to be a schematic readily available online for the 3120.

What I DID find, however, was a gutshot of the XXX, which many people have said is a direct ancestor of the 3120, and it appears to me that every tap coming off the power transformer is fused at the PCB. I would ABSOLUTELY pull the chassis and check the fuses on the board. If a fuse is solid (as in, not clear glass and rather ceramic) you should replace it anyway just to be sure, since you don't have a multimeter to test for continuity.
Tastes like chicken, if chicken was a candy.
#16
http://homerecording.com/bbs/equipment-forums/guitars-basses/tube-head-blown-fuse-why-320262/

Do you agree with what they are saying about this? Also if I pull the chassis and replace the fuse, isn't it likely that it will blow again if I turn the amp on possibly inflicting more damage? I just don't know much about this stuff really so I don't want to sacrifice some fuses that won't really tell me whats wrong and me have to take it to a tech anyway. Also I can get a multimeter tomorrow from my dad so how do you check fuses with it.

AFAIK the XXX and 3120 are EXACTLY the same. Everyone has said that so I would assume the schematic would be the same explaining why there aren't any of the 3120.

I can't get any info on what rating fuse to buy either. I even posted this on the peavey forums and got nothing. If that 10A fuse seems fishy then Im not trusting any of the fuse values and would like to double check.


Thanks for everyone's help.


edit: Getters are still silver.
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent
Last edited by bluestratplayer at Mar 18, 2011,
#17
Quote by bluestratplayer
http://homerecording.com/bbs/equipment-forums/guitars-basses/tube-head-blown-fuse-why-320262/

Do you agree with what they are saying about this? Also if I pull the chassis and replace the fuse, isn't it likely that it will blow again if I turn the amp on possibly inflicting more damage? I just don't know much about this stuff really so I don't want to sacrifice some fuses that won't really tell me whats wrong and me have to take it to a tech anyway. Also I can get a multimeter tomorrow from my dad so how do you check fuses with it.

AFAIK the XXX and 3120 are EXACTLY the same. Everyone has said that so I would assume the schematic would be the same explaining why there aren't any of the 3120.

I can't get any info on what rating fuse to buy either. I even posted this on the peavey forums and got nothing. If that 10A fuse seems fishy then Im not trusting any of the fuse values and would like to double check.


Thanks for everyone's help.


edit: Getters are still silver.


I would call Peavey and get info on the fuse ratings if no specs are printed on the PCB or chassis. Fuses blowing are meant to PREVENT damage, not inflict. Sometimes fuses blow for reasons that aren't very apparent, and you can replace them and the amp will work fine. It's when the amp repeatedly blows those fuses that I suspect a legitimate problem.

Fuses are consumables. Don't be afraid to use them. They aren't expensive like valves are, so you can afford to burn one or two in the process of troubleshooting.
Tastes like chicken, if chicken was a candy.
#18
Ok, I posted on the peavey forums for fuse ratings yesterday and still no response. I guess Ill have to call them. Im not worried about going through fuses, I just don't want to imflict more damage on the amp. As long as replacing them and turning it on won't cause any damage then I could care less cause I know fuses are about a dime a dozen. I will find out the ratings and order some fuses, I need backups anyway.
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent
#19
i'd take yours to a tech or apply for warranty service. It might just be that the tubes need to be replaced or it could be something else. at this point you don't know.
Jumping on dat gear sig train.
PRS Hollowbody II / BKP Warpigs
Strandberg OS6T / BKP Aftermath
Strandberg OS7 / Lace Poopsticks
Skervesen Raptor 7FF / BKP Warpigs
Skervesen Raptor 6 NTB / BKP Juggernauts
Hapas Sludge 7 FF / Hapas Leviathan
Anderson Baritom / Motorcity Nuke BKP Sinner Anderson H2+
Warmoth Baritone / BKP Piledriver
Ibanez Rg2120x / BKP Nailbomb

Blackstar ID:Core Beam
#20
I agree warranty service would be a good idea if the amp qualifies, but since BS is interested in tackling this himself, I've offered some input. I seriously doubt all 4 tubes would redplate at once due to failure, although it is possible. I'm still thinking bias supply.
Tastes like chicken, if chicken was a candy.
#21
Well I sold a guitar I had sitting around so I think Im just going take it to Craig. It doesn't qualify for warranty I checked that first. Plus Craig is close and I know he will get it fixed up. Anyway thanks for all the help guys.
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent