#1
My amp recently broke down (6505+ 112) and I'm wondering what could have caused this break.

The only way that I think it could have happened is as follows:
At college on last week, I was playing with it at college, and when I had finished, I left it on standby, but before I could power it down, my friend unplugged it at the socket. I wasn't pleased by this but thought no more of it. This Tuesday I didn't get a chance to practice, but as far as I know, nobody used it while they were practicing.

I should mention that its a head+cab now, and I never leave college without taking my kettle lead and speaker cable with me, to make sure people don't power it up without a load.

Anyway, I came into practice today, plugged my amp in and turned it on, and found no noise was coming out. On closer inspection, I saw the power tubes did not light at all.
So I checked the fuse on the back of the amp, and it seemed fine. I then took the amp out of the chassis and inspected the circuit board, and everything seemed in fine..except for one larger capacitor, which had a slight bulge in it.

I doubt the problem lies with preamp tubes, as the power tubes aren't working, and I doubt the power tubes have failed as I had no warning of this happening (as far as I know)

What could be wrong, and what may have caused it?

Thanks
#2
Unplugging at the socket on standby should not hurt anything. Do you have sound from the FX send? If I suspected the power section the FX send would be my first test point.
#3
Quote by ambler3
except for one larger capacitor, which had a slight bulge in it.
You (or god or whoever) may have ****ed a filter capacitor.
If that's the case, I wouldn't power it up again.

Pics would greatly help saying if you did.
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Clue: amplifiers amplify so don't turn it on if you need quiet.
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#5
I just had a very similar problem with mine a few days ago. I had just played a gig the previous week and when I got home and reconnected everything, I was having volume fluctuations and flat-out silence out of the amp. At first I thought it was power tubes, and indeed, one of them wasn't lit up.

As it turns out, that power tube had simply unseated itself a little, and also the sockets needed cleaning with contact cleaner (I just sprayed the tube pins and worked them in and out a few times). It works fine now.
#7
You shouldn't leave your amp where other people can mess with it.

Take that shit home with you.
#8
Quote by Dimarzio45
You shouldn't leave your amp where other people can mess with it.

Take that shit home with you.


I did all the time, about 2 weeks ago I started leaving it there. Depending if I can fix it, and what the damage/cause of damage was..maybe it was a bad idea
#9
Yeah, it can be a real pain in the ass taking it with you after a rehearsal. Sadly, there's no telling what happened to it when you weren't around. I hope you can get to the bottom of the issue without it being too costly.
#11
Um, well I got it used, but it's coming fairly close to a year i've owned it. So they probably are a year old or more.
But surely, i've seen from most people, power tubes rarely need changing, that, and as far as I know, they gave no signs of dying, which would point the problem at the circuit/connections?
#12
Depending on how often and loud you play, power tubes could easily wear out in under a year, especially the cheapie stock ones in the Peavey. And they don't always give signs of going out before blowing. Though the bulging cap also concerns me. That shouldn't be happening with an amp that new. Definitely take it to a tech.
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#14
Well, try the easy stuff first, obviously. But don't hesitate to take it to a tech if it doesn't solve the problem.
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#15
Reseat the tubes by all means first. I would even buy new power tubes and try that first to see if it is the problem as you would most likely need retube on power tubes anyway even if it is different problem. I'd personally get the tech to do that as well anyway.
#16
You need spares anyway. Buy a set and try them. If the power tubes aren't dead then you've lost nothing.
It's a 6505, you can just throw them in and try them. A 6505 is biased really cold, you can sit the bias control wherever it sounds best. Even at its hottest biasing it is still pretty cold so you won't blow anything up. The bias knob on a 6505 is a bit of a gimick really, that's why so many people mod the bias circuit on them.
Clean the tube sockets while you are at it.

The other day I thought I'd blown a tube - turned out that I'd forgotten to plug in the guitar.
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#17
Unless the 6505+ combo is different than the 6505(+) heads, then it doesn't have a bias trimmer.
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#18
I thought there was one inside it.
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Marshall JCM900 4102 (modded)
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Atomic Amplifire
Marshall 1960A
Boss GT-100


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#19
did you see if there was an HT fuse in there or if it blew?

i had one amp (IIRC it was a valveking head), that died randomly. checked fuses in the back were fine.

tubes were swapped, still the same.

then i pull the pan out and check the HT fuse (i am not sure all amps have them) but it was blown, a few nickles on a few new fuses, it was fine. i wasn't thrilled because i wanted to fix the issue, but never did it again as long as i had it.

i don't know how proper this is, but if i blow a fuse once, i don't worry about it. if i blow the second one, then i take it apart.
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#20
112 doesn't have a bias adjustment. Only the + head does but it will still be cold even maxed out.

Pictures of the capacitor?
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#21
Quote by R45VT
112 doesn't have a bias adjustment. Only the + head does but it will still be cold even maxed out.

Pictures of the capacitor?


+1 take a gut shot. if you could get to it and it is obviosu where, and can solder, it may not be that bad,

BUT DONT GO TOUCHING THINGS IN THERE, EVEN OFF IT CAN KILL YOU. DRAIN YOUR CAPS. IF YOU DON'T KNOW HOW TO DO THAT, MAYBE IT SHOULD GO TO A TECH.

chop sticks aren't a bad thing. so are pencils with the earser end going in.
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Quote by andersondb7
alright "king of the guitar forum"


Quote by trashedlostfdup
nope i am "GOD of the guitar forum" i think that fits me better.


Quote by andersondb7
youre just being a jerk man.



****** NEW NEW NEW!
2017-07-07 2017-07-07 Update and a Chat On Noise Constraints *** NEW FRIDAY 7/7
2017-04-13 RUN AWAY from COMPUTERS!!! TCE? RANT ALERT!!!
2017-03-02 - Guitar Philosophy 1001- Be Prepared For the Situation (Thursday 2017-03-02)
2017-02-21 How to Hot-Rod the Hell of your Stratocaster for $50! (Tuesday 2017-2-21)
Resentments and Rambling from a Guitar Junkie
---> http://trashedengineering.blogspot.com/