#1
I started a thread about this a week or two ago and I had let it die because I thought I found the problem. I was wrong... Long story short, I'm starting a new thread because the details of the problem are a little different now.

I have an early 1990's Fender Blues Deluxe and lately I've noticed some volume spiking when I play. At first I thought it was a problem with a pedal or cable, but I've been able to rule all that out (I've ruled out my guitars too).

First of all, the volume spikes seem to happen when I first start playing. It goes away after playing for a while. Second, I've realized that when the volume spikes it actually seems to be driving the amp harder too, it's not just a louder clean signal.

So, since the volume spike seems to add gain I though it might be a bad preamp tube. I swapped them all today but I'm still having the problem. I also read it could be a bad power tube, but I'm not sure if that's the case since I'm noticing an increase in gain as well. If it was a bad power tube wouldn't it just be a pure volume increase? The signal increase is definitely noticeable, but it's NOT loud enough to be causing power tube distortion. That leads me to believe the problem is somewhere in the preamp, right??

Since it goes away after playing for a while could that mean a bad solder joint somewhere? I don't notice any scratchy pots so I don't think it's them. Any advice would be much appreciated before I break down and just take it to a tech. Thanks!
Current Gear:
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#2
When's the last time you changed the power tubes?
If it's over 1 or 2 years ago, I would change out the power tubes.

Bad power tubes have many different symptoms, this may be one of them.
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#3
It may need a Cap job, it may need power tubes or a number of other things.

I'd swap the power tubes and then if it is still there take it to a tech and have them give it a once over
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#4
Quote by jakub421
When's the last time you changed the power tubes?
If it's over 1 or 2 years ago, I would change out the power tubes.

Bad power tubes have many different symptoms, this may be one of them.

I picked it up a couple weeks ago in a Craigslist trade, so I have no idea how old the tubes are. Replacing the power tubes was going to be my next step, but before I spend the cash on them I wanted to see what other people thought. It just seems strange to me that a bad power tube would add gain without become ear-piercingly loud at the same time. But I'm not a tech so I'm deferring to the experts here...
Current Gear:
2002 Gibson Les Paul Standard
'57 AVRI Fender Stratocaster
MIJ Fender Jaguar Special HH
Marshall JVM410
Vox AC15 C2
#6
^That. Don't listen to changing tubes every 2 years or whatever. Change them for the sound or if they are clearly going bad. More gain is not a power tube problem, most likely a cold joint on the potentiometers or feedback resistors as PSimonR said. Is there a change in tone or just more gain?
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#7
Quote by jjbarnes
^That. Don't listen to changing tubes every 2 years or whatever. Change them for the sound or if they are clearly going bad. More gain is not a power tube problem, most likely a cold joint on the potentiometers or feedback resistors as PSimonR said. Is there a change in tone or just more gain?

That's what I was wondering. And yeah, I guess you could say the tone is a little more harsh (in addition to being louder and driving the amp harder).
Current Gear:
2002 Gibson Les Paul Standard
'57 AVRI Fender Stratocaster
MIJ Fender Jaguar Special HH
Marshall JVM410
Vox AC15 C2
#8
Well getting some new power tubes is an easy thing you can do and swap yourself. Worst case, you've now got a set of spare power tube - which is always a good thing to have. I've seen power tubes that were over 20 years old, sometimes older, that work just fine. I've seen people buy new power tubes and they were crap out of the gate.

Try some JJs or Grove Tubes and report back.

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#9
Quote by 311ZOSOVHJH
Well getting some new power tubes is an easy thing you can do and swap yourself. Worst case, you've now got a set of spare power tube - which is always a good thing to have. I've seen power tubes that were over 20 years old, sometimes older, that work just fine. I've seen people buy new power tubes and they were crap out of the gate.

Yeah, I guess it makes sense to have a spare set anyway. I'm just cheap lol, and it'll bug me to buy a set and then have to take it to a tech anyway, who's probably going to try another set of new tubes and charge me for those too. But yeah, you're probably right...
Current Gear:
2002 Gibson Les Paul Standard
'57 AVRI Fender Stratocaster
MIJ Fender Jaguar Special HH
Marshall JVM410
Vox AC15 C2
#11
Quote by 311ZOSOVHJH
I'd contact someone like Doug at Doug's Tubes or Bob at Eurotubes and tell them you have a Blues Deluxe and need a matching set of tubes for that amp. Pop them in yourself, you don't need a tech to do that.

Sorry, I should have been more clear. I have plenty of experience swapping tubes myself. I meant that it will bug me if I pop in a new set and then it turns out to be an issue with a bad solder joint or something and then it'll still have to go to the doctor anyway. But that's probably a stupid way to think about it and I should just try the cheapest option first (new tubes, like you said). I'll pick up a set and report back with an update...
Current Gear:
2002 Gibson Les Paul Standard
'57 AVRI Fender Stratocaster
MIJ Fender Jaguar Special HH
Marshall JVM410
Vox AC15 C2
#12
Did you use contact cleaner on the new tube pins when installing? Maybe just some corrosion in the socket?
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#13
I thought I'd post an update in case anybody with a similar problem stumbles onto this thread. I discovered that when the volume spikes, the volume knob does literally nothing (turning up or down), the amp just stays at the spiked level. And if I switch to the dirty channel while the volume is spiked it instantly fixes the problem. So I think the issue is a bad volume pot on the clean channel. When I have the cash I'll take it to a tech to confirm / repair, but I'm petty confident that's the problem.

Thanks to everyone for the help
Current Gear:
2002 Gibson Les Paul Standard
'57 AVRI Fender Stratocaster
MIJ Fender Jaguar Special HH
Marshall JVM410
Vox AC15 C2
#14
Thanks for updating, if you get it to a tech and fixed, update again with what the actual issue was.
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