Marshall Valvestate Bi Chorus 200

[Vass]

I may try that. I'm not inclined to part it out first-shot without seeing if it works. Folks here seem to think it's a decent amp, and if it can be saved I see no reason to rip it up.

Does anyone here know anything about fixing them? WTF is an input transformer? Is it an easy fix?

Also- the layout of the 8280 is a bit different than the 8240....What would I need to bridge? Is it on the back panel? You'll note towards the end of the PDF that there's no loop or anything as you're describing on the front panel....A description of what's on the rear panel can be found on page 6.....which do I need to jump?

http://www.marshallamps.com/download...0hbk%20Eng.pdf

I'm very slow & stupid, so I really appreciate the help.


Vass

[yard dawg]

Id save it. They are great sounding amps.

[OnlineStageGear]

Input Transformer? That's a new one. Out of all the amps I have fixed I have yet to run across an input "Transformer".

Just for shits, take a 1/4" patch cord and bridge the effects send and return and see if it works. I had an 8040 that "died" and that's all it was. The jacks were oxidized and the little switches in them got stuck.

+1. There are contacts in an effects loop jack that when there is no plug plugged in, It is supposed to close the contacts and with a plug opens the contacts and sends the signal through the loop. Finger oil alone from the plugs can end up building up on those contacts keeping them from closing when there is no plug plugged in not to mention all the other foreign debris that can get in there. BTW, $100 bench charge is a little on the steep side.

[Vass]

Alright, I spoke to him. Going to go try to pick it up tomorrow or the next day. He did say input transformer. Also said the difficulty is that it could be a matter of a single capacitor that's fried on the board, and you'd have to go through them one by one & know what you were doing to get to it. But he said the output transformer is def working, because the amp DID power up, it did make "dirty pots" noise when the settings were messed with, but no sound when a guitar was hooked up.I will try your suggestions guys. I know that if I screw around inside it I can get a nice sparky from the capacitor, so I'm going to avoid that. I have no idea what I'm doing, frankly. But anything you can think of suggestion wise would be huge.I thought the bench charge was a bit on the high side- that was purely for diagnostics. I appreciate that professionals deserved to be compensated, but we're getting into some pretty high end territory there.
Vass

[CharvelRocker]

If you ask me, I think it sounds like little more than a bad jack. There is a smaller transformer on all amps, but I thought it was the input voltage transformer, with nothing to do with the actual signal at all. And if that was the case, it would even power amp.

[Vass]

CharvelRocker- Not sure I'm understanding what you're saying (told you I wasn't bright). You think it sounds like a bad jack, or sounds like something more than a bad jack? And the input voltage transformer, are you saying it WOULD or WOULDN'T even power up if that was busted?

Guys thank you for your input on this, and very sorry for my ignorance.

Vass

[yard dawg]

I would have it fixed by someone who doesnt bend you over to do it. $100 is steep.

[CharvelRocker]

Sounds like a bad jack to me is what I meant. And if the transformer for the input was busted, it would not even power up.

[OnlineStageGear]

Bad Jacks and loose solder connections are the most common failure for guitar amps.

[bibz]

Stirring my memory up, on two of the 8240's the families had they've needed attention with the input jacks. Cold solder or dirty contacts, so my moneys on that being the case, moreso the input jack!

[Vass]

IT'S ALIVE.....AAAAAALLLLLIIIIIIIIIIIVVVVVVEEEEEE!!!!!! !

The pots are shot, I guess....they crackle like mad. The bass on the boost channel doesn't seem to do shit. I boosted the boost channel volume to max, gain to max, and put master @ 9 o'clock....not very loud. Sounds like as I turn it (crackle crackle) that at any second I could blow myself through a wall.... Chorus works FINE, both modes, did not try the footswitch. Reverb works FINE. Clean channel works as well, just fine but for what I'm perceiving as a master volume issue.

So it needs work! I have no idea how to clean pots, seems like I have to attack from the back of the unit, which I don't want to do. BUT SHE CAN BE SALVAGED!

Can't believe it. Thought it was fuckin' dead for sure. Sounds like there are still issues, but not fatal ones, at least not yet. The bass thing concerns me the most- I guess something could be fried on the board that would do that.

Thanks again for your help, and any suggestions would be MUCH APPRECIATED! It's only because of you guys I gave it a second shot at home.

EDIT TO ADD...OOOOOOooohhhhKAAAYYyyyyy almost gave my fiancee a heart attack, and please excuse me while I change my underwear...... Fooling around with the mid pot on the clean channel and she came back for a moment BLARINGLY loud.

I will not be doing that again until I get the pot situation figured out.

Shit, that was loud. Master at 9 o'clock.


Vass

[CharvelRocker]

Alright, what you need to do is pull out the chassis. The pots should have a little opening in them on the side, probably facing up at you. Spray a little contact cleaner in there. As for the switch, I have no clue if you can put contact cleaner in it or not without seeing it to look for the opening, but I would be a bit surprised if you couldn't.

[yard dawg]

yea take the amp chassis out and look for loose solder joints. The contact cleaner will help the pots. Its worth saving dude. Those amps really do sound good.

[Franx]

IT'S ALIVE.....AAAAAALLLLLIIIIIIIIIIIVVVVVVEEEEEE!!!!!! !
...
I boosted the boost channel volume to max, gain to max, and put master @ 9 o'clock....not very loud. ...
Fooling around with the mid pot on the clean channel and she came back for a moment BLARINGLY loud...

I have the boost channel volume & gain at ~ 3 and the master vol at 9 o'clock on my 8240 - and it's really loud !!!

So once you fixed the pot-issues, you won't be disappointed

[bibz]

haha as I was reading that I thought to myself I hope he doesn't die if whatever pot is playing up contacts properly all of a sudden!!

A bit of playing around but the chassis does come out quite easily. While there you can check for any ill signs on the pcb, checkout the tube (probably a 'marshall' branded one) and as said clean up the pots and check the solder on them and the jacks.

Congrats on bringing her back man!