# Marshall Valvestate Issue



## GuitarsCanada

I have an older Marshall Valvestate 80V here that I picked up a few years back. It loses volume for an unknown reason, just tapers off. If you play around with the volume knob it will come back. Just seems that it almost loses power all of a sudden but I don't think that is what is actually happening.

Throw her in the scrap heap or is it a simple issue?


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## fraser

i have one of these, had it for years- knock around kind of amp lol.
ive had a similar problem, had to replace a few of the pots, as well the solder joints at the board(from the pots) seem to lift, and needed to be redone-
had a few problems like this with it, but all simple fixes.


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## fraser

sorry scott- i wrote that post first thing in the morning, was just having a smoke before leaving for work- now that ive got more time ill try to elaborate.

ive had this problem with my amp several times- once when it was new, and still under warranty.
each time same symptoms as yours- its fine, then loses volume suddenly- fiddling with the volume knob brings it back-

thing with this amp is that the pots are mounted to the circuit board- the shafts poke thru the front panel and are secured there. im almost positive that the first time it happened, while the amp was under warranty, one of the lugs was not firmly soldered to the board, and resoldering that lug fixed it. this was in 91 or 92 or something, so the details are blurry, but im positive i recall doing this.
also, im 100% positive that at the later occasion, not having a replacement pot handy, i took the one out of the clean channel and put it in the dirty channel- fixed the problem, until a few years later that pot went as well, and i bought a replacement. my channel 1 has never been replaced lol.

easy enough fix- youve got to undo all the pot nuts on the front panel, as well as the input/output jack nuts, and all the screws that hold the chassis into the cabinet, then slide it out. thats the biggest hassle of the whole job.
i dont recall if you need to remove the board to access the solder joints however, if so its only a few screws.

i found it a strange problem to have with an amp- and for it to re-occur is strange too. strange amp. i ended up with mine because all my amps were dead and a student had just bought this one but didnt like it and wanted a big bag of pot that i had.


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## nonreverb

What a coincidence...I just finished a 100V repair. Check all the large resistors on the board. They get solder cracks. As stated by Fraser, the pots are crap in these things. You will probably have to replace the gain and volume pots. Check the loop in/out jacks. If you have some clean spray, put a couple of shots in both jacks and then insert a plug in a couple of times so the cleaner covers the contacts. One more thing, check the input jack solder joints. Hope this helps.:smile:


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## Peter

Had the same problem with my old 8080, was bad soldering. The pots seem to go extra quick too.


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## GuitarsCanada

I have some time today, I will pull it apart and start to look around. Thanks for the info boy's. It's not a bad sounding amp, at lease to my ears.


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## GuitarsCanada

*Guts*

Here is the chassis. The thing-a-ma-bob with the arrow is totally loose. Wobbles all over. Does not come out but is clearly loose. Question is how do you get under the board? Will it come away from the actual chassis. Appears to be rock solid on there.


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## Wild Bill

GuitarsCanada said:


> Here is the chassis. The thing-a-ma-bob with the arrow is totally loose. Wobbles all over. Does not come out but is clearly loose. Question is how do you get under the board? Will it come away from the actual chassis. Appears to be rock solid on there.
> [


Geez, I swear Marshall hired the mentally handicapped under a work co-op program when they soldered up their ValveState series! Always it's poor soldering issues.

To get the board out you'll have to undo the nuts holding all the controls. There's probably a few screws pinning down the board as well. You may have to unplug a few connectors if they get in the way. Note the plastic spacers that are the same style as used to hold motherboards in computers.

You may not have to totally remove it. Hopefully you can free it up enough that you can rotate the board 90 deg up so that you can get at the bottom solder foils. 

The wobbling part is an electrolytic capacitor. It has two leads coming out the bottom that go through the board and are soldered to the traces on the other side. Once you can get at the solder points if you heat them up and maybe add a touch or two of solder things will be ok again.

Be very careful not to heat the hell outta the solder joint! The copper traces on the board are kinda chintzy and might peel off and break. Then you'll have to try to take little bits of bare wire to jumper the breaks - a PITA.

The good news is that after you've eventually resoldered all the hundreds of connections to the circuit board the ValveStates become reliable amps!:smile:

:food-smiley-004:


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## GuitarsCanada

well, that fixed that problem. It was that loose capacitor. But you are right, the pots are crap. They are as scratchy as hell. I will get around to changing those at some point. 

Thanks for the guidance boy's. Another problem solved through GC !!!


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## nonreverb

GuitarsCanada said:


> well, that fixed that problem. It was that loose capacitor. But you are right, the pots are crap. They are as scratchy as hell. I will get around to changing those at some point.
> 
> Thanks for the guidance boy's. Another problem solved through GC !!!


Did you happen to resolder the two power resistors beside said cap? If not, you'll have to in the near future as I can see the browning on the board benieth them...a sign that the solder is probably in bad shape...


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## greco

GuitarsCanada said:


> well, that fixed that problem. It was that loose capacitor.........


Well done...Congrats :bow:

Did you end up resoldering the power resistors also?

Cheers

Dave


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## GuitarsCanada

nonreverb said:


> Did you happen to resolder the two power resistors beside said cap? If not, you'll have to in the near future as I can see the browning on the board benieth them...a sign that the solder is probably in bad shape...


Negative on that. I did check every single one though to see if anything looked like it was going or loose. But now that I know how to get it apart, which is not too bad actually, I would be able to affect similar repairs in the future.


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## greco

GuitarsCanada said:


> I would be able to affect similar repairs in the future.


Can I bring you my Fender M-80...it needs 3 new input jacks (I have the parts)

j/k.....9kkhhd

cheers

Dave


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## GuitarsCanada

greco said:


> Can I bring you my Fender M-80...it needs 3 new input jacks (I have the parts)
> 
> j/k.....9kkhhd
> 
> cheers
> 
> Dave


I find it easy to take them apart, not so easy sometimes getting them back together. Let's tear it up !!


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## fuzzface74

Yes, pretty poor workmanship on these valvestates. I have a 40 watt that does the same thing as the OP. My solution is with the 'power amp in' jack. I have to jumper the pre-out to the pwr-in to fix the problem.

Other than that, all the pots are scratchy - the clean volume pot cuts out completely sometimes. Still, it's not worth the hassle of selling it.


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