Hello, World!
I few years back I saw a used Marshall Valvestate 8040 nearby for a good price, but when I contacted the owner he decided to give it to his brother... Fast forward to this month and I saw the same model elsewhere for a good price, since I always wanted to try it and drove to pick it up.
The ad said "the pots scratch a bit, but otherwise works perfectly", he wanted 50 bucks for the amp, so I thought it was ok. I tried it and ALL the pots were very scratchy, some with dead spots and the volume was coming and going. He said that it had been stored for two years with no use, but his brother (an electrical engineer) had said that the pots needed cleaning and it would be as good as new. He also reduced the price to 20 bucks on the spot. I reluctantly accepted the offer, as I had driven for almost two hours and didn't want to come home empty handed.
I tried again at home and no change, of course, I had only changed it's location. Next day, I borrowed some electrical contact cleaner and sprayed all the pots from behind, this meant removing the metal casing holding the electronics from the box. I turned them a few times, let them dry and then cleaned again. I also sprayed and cleaned the switches and the jacks. I also cleaned the reverb tank and contacts.
When everything was dry I assembled it and tried again. Surprise, the cleanchanel works! Although the treble pot scratches a bit, I now could adjust gain, treble, mid and bass. The reverb works too! The amp is pretty loud, so I never went over 5 on the volume, imagine if it would go to 11! I tried the boost channel and it did not work. I mean, there is a faint distorted sound coming out of the speaker as I play, so something is working inside. Contour and bass knobs seem to do something, but the gain, volume and treble don't, the channel seems to be stuck on a high-gain low-volume setting.
I am very disappointed that my new-to-me amp is not working, but I am keen on looking for the problem and solving it!
This is what I've tried so far:
What do you think?
Any advise will be greatly appreciated!
I'll keep you posted!
Cheers,
Walt
I few years back I saw a used Marshall Valvestate 8040 nearby for a good price, but when I contacted the owner he decided to give it to his brother... Fast forward to this month and I saw the same model elsewhere for a good price, since I always wanted to try it and drove to pick it up.
The ad said "the pots scratch a bit, but otherwise works perfectly", he wanted 50 bucks for the amp, so I thought it was ok. I tried it and ALL the pots were very scratchy, some with dead spots and the volume was coming and going. He said that it had been stored for two years with no use, but his brother (an electrical engineer) had said that the pots needed cleaning and it would be as good as new. He also reduced the price to 20 bucks on the spot. I reluctantly accepted the offer, as I had driven for almost two hours and didn't want to come home empty handed.
I tried again at home and no change, of course, I had only changed it's location. Next day, I borrowed some electrical contact cleaner and sprayed all the pots from behind, this meant removing the metal casing holding the electronics from the box. I turned them a few times, let them dry and then cleaned again. I also sprayed and cleaned the switches and the jacks. I also cleaned the reverb tank and contacts.
When everything was dry I assembled it and tried again. Surprise, the cleanchanel works! Although the treble pot scratches a bit, I now could adjust gain, treble, mid and bass. The reverb works too! The amp is pretty loud, so I never went over 5 on the volume, imagine if it would go to 11! I tried the boost channel and it did not work. I mean, there is a faint distorted sound coming out of the speaker as I play, so something is working inside. Contour and bass knobs seem to do something, but the gain, volume and treble don't, the channel seems to be stuck on a high-gain low-volume setting.
I am very disappointed that my new-to-me amp is not working, but I am keen on looking for the problem and solving it!
This is what I've tried so far:
- Check speaker contacts (ws fine)
- Clean all pots, switches and jacks (better, but still not ok)
- Bridge the pre- and power-amp jacks with a patch cable (this is a known issue, but no change for me)
- Blow some air into the pots to remove any remaining crap from the inside
- Check the solder joints
- Re-flow pot solder joints carefully
- Any ideas?
- After a quick look at the board, nothing seems broken or burnt to my (un)experienced eye, but I'm attaching a few pics in case some of you see something that I have missed.
- I don't think that the tiny 12AX7 tube is problem, as it works only for the clean channel, and that seems to be ok now.
- I've seen new pot sets online, but they sell for a lot compared to what I've paid and to a compareble new amp, so I won't go that route.
- I don't feel that I'm at a total loss, just bummed out. In the worst case, I could sell the parts and recover my "investment". Or just rewire the speaker and use it as a cabinet for other amps.
What do you think?
Any advise will be greatly appreciated!
I'll keep you posted!
Cheers,
Walt
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