Guys,want to help me fix my Marshall valvestate/

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Guys,want to help me fix my Marshall valvestate/

Postby Aharon » 28 Jul 2012, 02:31

I've owned a Marshall Valvestate 8080 for 15 years or whenever they came out but only played it for a bit and shelved it.
Should've known better myself but after not being turned on for more than a decade first thing I should've done is change those caps in the power supply(I'm assuming that's what went wrong ).To make a long story short I turn on the amp and start playing and about 20min to half hour later the volume just cuts off,the fuse did not blow,pilot light still on and no fireworks or nasty growling or ungodly noises.The ONLY thing was a slight overheated electronics smell(not burnt smell)and after noticing that I promptly turned it off.

Anybody wants to walk me through fixing this?

by the way,the old members might remember me,I'm Aharon ,I've been away for a while but I'm trying to come back and this project might be perfect,I'm a little rusty but hey.
I have successfully built about 20 tube amps but ss is a different animal and like I said I haven't touched a soldering iron in years.
With that said,hope somebody helps me rescue this amp.
Thanks :D
Aharon
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Re: Guys,want to help me fix my Marshall valvestate/

Postby lolbou » 28 Jul 2012, 08:24

Aharon wrote:To make a long story short I turn on the amp and start playing and about 20min to half hour later the volume just cuts off
The 8080 is "cold solder joint park"...

Aharon wrote:The ONLY thing was a slight overheated electronics smell(not burnt smell)and after noticing that I promptly turned it off.
Some parts in it are expected to turn hot indeed (power resistors), but that's just normal, and shouldn't smell that much. Did you look inside to see?

To somehow check where your problem stands (provided your +15V/-15V is good, along with the regulating zeners), plug your guitar in the RETURN jack to check if you get sound out of the power amp...

Schems are available here (Valvestate Mk.1).
- Are you a mod or a rocker?
- Uh, no, I'm a mocker.
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Re: Guys,want to help me fix my Marshall valvestate/

Postby nickthemen » 28 Jul 2012, 13:32

Spray al in and output jacks, its a common problem with these amps, this wil fix it 9 out of 10.
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Re: Guys,want to help me fix my Marshall valvestate/

Postby Aharon » 29 Jul 2012, 00:00

Thanks for the replies guys.
I opened it up and nothing burnt or black,not even brownish.
I will clean those jacks,follow the advice ,check for more clues and report back.
Thanks
Aharon :applause:
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Re: Guys,want to help me fix my Marshall valvestate/

Postby Aharon » 30 Jul 2012, 18:42

Ok,took it completely apart and yes looks like some cold joints were fixed before it left the factory.
I cleaned the input jack and checked for track bridges,there was a lot of splatter in some of the joints,cleaned that and looked for trace cracks with a light behind the board...nothing I could see.
cleaned some other contacts like the reverb jacks etc and reassembled.
Plugged it in the input jack and nothing,tried the return and got sound,good.....
Then started to twist every knob on the amp and a few were scratchy.All cleared up prett much except the boost channel Volume and the effect's wet/dry knob in the master section.These are bad enough that when I turn those the sound cuts on and off.The amp is playing now and sounds ok. I'm guessing that if those pots don't clean up I should replace them.

Waiting for some input
Thanks
Aharon :applause:
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Re: Guys,want to help me fix my Marshall valvestate/

Postby lolbou » 30 Jul 2012, 20:51

Aharon wrote:I'm guessing that if those pots don't clean up I should replace them.
I did replace nearly all pots in mine (= common issue) though contact cleaner did help some time before replacing those... Banzai had exact replacement, but an alpha pot with long shaft (to adjust to your needs) and tab removed would work fine...

See below an actual Marshall (from my late 8080 :cry: ) and a long shaft alpha:
potsi.jpg

potso.jpg
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Re: Guys,want to help me fix my Marshall valvestate/

Postby Aharon » 30 Jul 2012, 21:08

Thanks a million lolbou :mrgreen:
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Re: Guys,want to help me fix my Marshall valvestate/

Postby Aharon » 06 Nov 2012, 20:23

Just an update , got plastic safe contact cleaner and sprayed the heck out of the pots ,switches and jacks.....the amp is as new.
Thanks everybody
Aharon

For this message the author Aharon has received thanks:
lolbou (07 Nov 2012, 09:16)
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Re: Guys,want to help me fix my Marshall valvestate/

Postby lakesidepark » 18 Sep 2017, 19:55

Did you look for Marshall potentiometers in tubes and more. Did you look for correct schematic form you amplifier, sometimes MArshall makes 2, 3 variations of same circuit amplifier, by the years.
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