#1
I bought this Marshall Valvestate S80, 40 watts (model 8240), from a friend today. I got it pretty cheap because we knew that it wasn't in it's best condition.

Anyways, directly when I turn the amp on, I get a pretty loud buzz/hum or whatever you could call it. It's there even when all the knobs are turned off and I tried all the buttons but it won't go away.

Well, that's not really the big problem. This is really wierd and I don't know really how to explain it. The thing is, when I start to play, I get this really wierd sound, almost as an effect was still on, like flanger/chorus or maybe a reverb, even though all the effects are turned off. I get this on both channels, but I believe it's worst on the gain one. I can turn it up pretty loud and still play as usual but it sounds like crap, not like a speaker has been blown, but just that freaking wierd, bad sounding effect.

My friend telled me about how it first got there. I wasn't there when it happend so I'm not entirely sure but this is what he said happened;

He just got it, but I think it was from the 90's or something, turned it on and it played really good, then he put on some reverb. But he was rehearsing with his band so I guess he took the volume all the way up. Then he took his (dist?)pedal between the amp and the guitar but when he turned it on he heard some kind of sound/pop/boom, I don't know. And after that, it sounded really wierd, kind of like it does now, I guess. But then when he switched to the clean channel it was all good.

The next day when he turned it on though, it sounded just like it did when the accident had happened the day before!

I'm sorry for this wall of text, but does anyone of you have an idea what could have happend and if there's any way to make it work good again?

Thank you, hoping to get some kind of replys, hehe.

Peace
#2
Blown something, probably. Tube, fuse, something.
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#3
How could I check what's been blown then? Just take it to a tech? What could it cost?

Thanks for the reply!
#4
To make sure I understand you right he took the amp to 10 for an extended period of time then decided to throw a distortion pedal infront of it?

More then likely the amp was hella clipping and already running at the verge of melt down from the heat being generated and with the added boost the pedal gave it. The amp finally gave out. Probably fried one of the internal parts which what the loud pop was.

Also those amps blow up all the time, there not to sturdy of an amp and generally past 5 on the volume there clipping like crazy.

Take it to a tech and have him check the pcb for blown parts..

Hell I even have one of the boards that blew up sitting beside my work bench i use for parts when they come in. Those amps and AVT's are my number one customers lol
Last edited by IbanezPsycho at Aug 7, 2008,
#5
Ok, thank you, I'll probably get it to a tech next week or something.

But besides from this, are these good amps? I don't know anything about them really...
#6
Ohh and easiest way to tell is smell the back of it.. If you smell a strong burnt electronics odor then take it in but with most SS amps the cost to fix it out ways the cost of just buying something else. The good thing is you can part that one out on ebay and make some cash back.
#7
But the wierd thing is that I can still play it, at a pretty loud volume, it's just that that it sounds like an effect is still on, but it isn't?
#10
How many watt is it?
Guitars: Fender Highway one -08, Epiphone SG, Walden acoustic and two parlour-acoustics from the early 30's
Amps: Fender -65 Deluxe Reverb, Marshall Valvestate 8240, Peavey Rage and one unknown one, hehe...
Pedals: Dunlop Fuzzface, Original Crybaby
#12
open it up and see if anything's burnt?
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#13
Would it be obvious if anything is burnt? Or do you mean open it up and test everything and stuff like that? Because I don't really have any experience with that at all...
Guitars: Fender Highway one -08, Epiphone SG, Walden acoustic and two parlour-acoustics from the early 30's
Amps: Fender -65 Deluxe Reverb, Marshall Valvestate 8240, Peavey Rage and one unknown one, hehe...
Pedals: Dunlop Fuzzface, Original Crybaby
#14
Alright, here is my trouble shoot:

Blown fuse? No power
Blown tube? Would sound like ass
Broken/burnt ground? Would buzz. check all the jacks on the amp and the power supply cable
Possible Cooked Component? Maybe, look inside for anything on their that is blackened, dead give away
Bad Transistor? I list this separate as the pedal could of caused the already pushed transistors to clip harder, which could damage/overheat them
Bad Speaker? Possible, though unlikely it could of been over-stressed. Try visually inspecting it.
#15
Well, now I took out the tube in the preamp, just have to replace it. I found a new tube in my room, new & sealed of course, but I don't know if it would fit.

It's a "groove series, electron tube" On the tube it says GT12AX7C.....

It also says "ECC 83" on both this one, and the old tube which I took out of the amp

Would it work to just put that one where the old one was or would I blow it up?


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EDIT: I tried and it worked, I believe that the sound is improved but with that buzz it's hard to even hear it.

I also noticed that the buzz is in the key of G (?!) so when I play in G it sounds okay, hehe...

But what could be the cause of this buzz? Broken/burnt ground, bad transistor or some cooked component?

I don't know..

Thank you for your help this far, it's been awesome, but now I need help to solve this buzz problem....
Guitars: Fender Highway one -08, Epiphone SG, Walden acoustic and two parlour-acoustics from the early 30's
Amps: Fender -65 Deluxe Reverb, Marshall Valvestate 8240, Peavey Rage and one unknown one, hehe...
Pedals: Dunlop Fuzzface, Original Crybaby
Last edited by FiliphSlim at Aug 12, 2008,
#17
Well, I've tried switching the tubes and it worked, I believe that the sound is improved but with that buzz it's hard to even hear it.

One thing I noticed is that the buzz from the amp, is in the key of G (?!) so when I play in G it sounds okay, hehe...

But what could be the cause of this buzz? Broken/burnt ground, bad transistor or some cooked component?

I don't know..

I also believe there's also a huge loss of volume. I haven't heard a new, fully working one, but with this amp, I can sit right in front of it without being bothered because it's loud when everything is on 10...

Thank you for your help this far, it's been awesome, but now I need help to solve this buzz problem...
Guitars: Fender Highway one -08, Epiphone SG, Walden acoustic and two parlour-acoustics from the early 30's
Amps: Fender -65 Deluxe Reverb, Marshall Valvestate 8240, Peavey Rage and one unknown one, hehe...
Pedals: Dunlop Fuzzface, Original Crybaby
#18
I heard someone say that it probably was a failed power supply capacitor.

If so, is that anything that I can fix by myself, if so what would it cost? Or should I just take it to a tech?
Guitars: Fender Highway one -08, Epiphone SG, Walden acoustic and two parlour-acoustics from the early 30's
Amps: Fender -65 Deluxe Reverb, Marshall Valvestate 8240, Peavey Rage and one unknown one, hehe...
Pedals: Dunlop Fuzzface, Original Crybaby
#19
Quote by FiliphSlim
I heard someone say that it probably was a failed power supply capacitor.

If so, is that anything that I can fix by myself, if so what would it cost? Or should I just take it to a tech?


If you are asking that question your best bet is to take it into a tech.. At minimum probably will cost you about 50-60 bucks