#1
I have a Peavey Windsor head, bought it two years ago from a recording studio. Had to replace a preamp tube a few months ago, no biggie. The other day, the volume dropped to probably 10% of what it was. Opened it up and tapped all the tubes with a pencil. The very first preamp tube behind the input jacks would make noise through the speaker, the rest (including the one I changed earlier) were silent. Swapped it with a different tube, same problem.

The inside of the amp was extremely dusty so I wiped it down with a dry cloth. I believe that the socket might be dirty. I was told to use contact cleaner, but it had to be a certain kind (deoxit 5 I think) Is that something that a local hardware store would have?

After wiping the amp down, I pulled all the preamp tubes out and pushed them back in very snug. Problem went away but came back after about ten minutes of playing. I've read about socket retensioning, but the socket doesn't feel loose at all. In fact, quite a bit of pressure is needed to put the tube into it all the way. If that was the problem, would the tube "feel" loose?


In short, my tube amp is losing volume. I think it's the first tube socket, but I'm not sure how best to fix the problem. Can anybody help out? Thanks in advance!
#2
Replace the tubes and get on with life.

V1 will almost always have a slight microphonic characteristic.
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#4
If you want to try cleaning the sockets, any kind of contact cleaner would work
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#5
If your volume has dropped change the power tubes
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#6
You tested for microphonics only. Therefore, all you found was a microphonic tube. Sounds to me like you need new power tubes too.
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#7
I'd try swapping all your preamp tubes first. Swap them one by one and see if the problem goes away. If it doesn't it might be a power tube. Even if one power tube goes you need to replace them all, but keep any good ones as spares for emergencies.
#8
I was not aware that test only checked for microphonic tubes, thanks for pointing that out!

Why do I need to change all the power tubes if only one goes bad? I've heard of people pulling the inside/outside two power tubes to run their amps at half wattage, could I do this to try and find the offending tube(s) to make sure that's the problem without hurting my amp?

Also, if I replace all four power tubes with the exact same make and model that are currently in the amp, will the amp have to be rebiased?
#9
Quote by Tracii Lee
I was not aware that test only checked for microphonic tubes, thanks for pointing that out!

Why do I need to change all the power tubes if only one goes bad? I've heard of people pulling the inside/outside two power tubes to run their amps at half wattage, could I do this to try and find the offending tube(s) to make sure that's the problem without hurting my amp?

Also, if I replace all four power tubes with the exact same make and model that are currently in the amp, will the amp have to be rebiased?

You replace them all be cause they are a matched set

If the amp was in a studio and then you have had it for 2 yrs. I can confidently say your powertubes sound like the culprit from the info you have given here.

I'm pretty sure the Windsor will let you run with 2 tubes. Pull either the inner 2 or outer 2 and run the ohms different.
If you had a 16 ohm cab then you switch your amp to 8 ohms. If it was 8 then you switch your amp to 4 ohms.
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#10
Yeah, basically you're checking for the sound through the amp. By swapping a preamp tube one at a time you are eliminating which one could be the issue - since it's rare that two tubes would go at once. I wouldn't try running half the tubes. Im 99% sure The Windsor is a fixed Bias, so you cannot adjust it easily.

Power tubes are basically "paired" to work together better. I think it's to do with the amount of wattage. Try reading online for more info on it.
#11
I will definitely try the preamp tubes first, since that was what went out on me a few months ago, and they're much cheaper. I'm a little confused about the power tubes. Would running it with only two power tubes really hurt the amp if it wasn't for an extended period of time? And if the bias is fixed, does that mean I would or wouldn't need to change it if I replaced the power tubes with identical ones?

I don't know anywhere near enough about electronics to try and rebias my amp on my own, so if it needs to be biased it will be done by a proper technician. I'm just not understanding if it HAS to be rebiased or not. Maybe it wouldn't be a bad idea either way since the bias can drift? This is my first all tube amp so I'm trying to learn as I go
#12
Yes, you can test that way. On those V4 and V5 are a pair and V6/V7 are the other pair.
When you pull two power tubes you need to switch the impedance to half of what the cab is.
You may find that you actually prefer running two tubes. If so still buy matched quads so you can replace single tubes from that set in future. That's what I do. I only run half the tubes but as I bought a quad I have two matched tubes in my toolkit for spares, I know I can just throw one in if I have a failure and the bias should be ok.
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#14
As for power tubes, the usual advice stands. SED =C= if you can afford them, JJ if you can't. JJ are the best value for money.
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Marshall 18W clone
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Marshall 1960A
Boss GT-100


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