Amp Woes

[Lazy_McDoesnothing]

I left my Peavey Classic 30 all tube amp over at our (humid)practice space basement for a bit too long and it developed a problem.  It crackles and pops from the moment I turn it on(guitar unplugged) and never goes away.  It's probably time for a tube change anyhow but I'm wondering if it's maybe a bigger issue.  It'd be great if you guys could chime in on anything it could be.

I recorded a short clip(Peavey Krispies 30) of it in case it would help.  All that crackling is directly from the amp, not from some digital multieffect to simulate an old record.:roll:  I had the SG out so I played a little AC/DC for kicks.

Also recorded a short clip(motorboatin' s.o.b.) of another problem on my Mesa Nomad.  It has a low rumbling motor boat sound (capacitors? tubes?).  Please help!

http://www.soundclick.com/bands/default.cfm?bandID=803296

[Lazy_McDoesnothing]

Just adding that I noticed the Peavey sounds very muffled and muddy.  Also bumping this up to get some help.  :o

[Fourth Feline]

Hard to give a definitive cause for the motorboating on the Mesa, for in theory it would suggest components in the path of a valve cathode changing value over time, allowing the amp to 'runaway'  . A tech would have to explore that one in person.

On the Classic 30 I would :

 1) Clean the valve pins and sockets with 'Servisol' which you can get from Maplin - or some WD40 used sparingly. This should clean out any problems brought on by oxidisation of the surfaces causing intermittent contact. gently wiggle each valve in it's holder, but not enough to loosen the grip of any individual pin holder - just enough to work the fluid in between the pin surface and pin holder surface.

2) Very gently tap the side each pre -amp valve with a pencil, to see if any one is more microphonic than the rest.

You have already said that you are willing to re - valve but first let's assume that the problem has occurred due to the condition the amp was stored in, therefore clean ( as at point '1' above) - and if you can reach in safely, spray your control pots with the Servisol too and give them a few turns back and forth to work it in.

I hope that starts the ball rolling.

[Lazy_McDoesnothing]

Thanks for that.  I'll use a very light bit of wd40 as I have that on hand.  It'll have to wait till tomorrow though since it's 3:30 AM over here and I need to get to bed.  I'll post back here tomorrow.

[Bird]

I have a classic 50 and was having some crackling and popping issues as well. The original tubes were still in it (about 10 years) and once I swapped them out problem solved. I got mine through Eurotubes online. May not be the problem you're having but it's a definite possibility.  :)

[Lazy_McDoesnothing]

Update:

I found some Isopropyl Alcohol lying around so I used that instead of WD40.  I took out every tube one at a time and inspected and sprayed the pins a little and put them back in and wiggled them.  One thing I noticed was that the preamp tube in the V1 position looked like it had a lot of white corrosion on it up near the top of the pins closest to the tube.  The rest had virtually none whatsoever, maybe a little "dull" but not bad at all.  I'd say the tubes are about 2-3 years old except the V1.  I already replaced that one but I don't remember whether I replaced it because it was bad or because I was trying out different brands.  It was a Groove Tube Mullard.  I also tapped the tubes and there was no noise out of the ordinary other than the actual tap.  The V1 did seem a bit louder compared to the others when tapping with the same force.  Dunno if this is normal or not.

End results after cleaning the tube pins, sockets and control pots is the crackling is still there.  It seems it has gotten maybe slightly better.  Although it may be just my wishful thinking :oops:  

I think I'll just get a replacement for the preamp tube in the V1 position as the others seem completely fine and if that doesn't solve it I'll either re-tube the rest and/or take it to a tech.

Thanks for the help guys.

[Elliot]

The Classic 30 has an EL84 power stage - I think.  EL84s are not long life tubes and 3 years of use of an EL84 is likely to dull the tone a substantial amount - Do you have any spares to test the power tubes?

[Lazy_McDoesnothing]

Nope, no spares.  I do crank this thing pretty regularly at practice so it's likely that it's time for a re-tube.

[HTH AMPS]

V1 is the most sensitive spot - swap the preamp valves around and see if that makes any difference.  If it's a bad preamp valve, it most certainly will.

You could also try pulling the valves starting with V1 and see if the noise stops when you pull V1 out.

The motorboating on your other amp could be a failed smoothing cap/insufficient filtering in the preamp or lead-dress.  It's a tough one to track down without a scope.

[Bird]

After 3 years of use it's probably a good idea to change all the tubes. With heavy use I believe it's recommended they be changed once or twice per year. Someone can correct me if I've got my info wrong.

[Lazy_McDoesnothing]

Well it looks like for now it's just the V1.  I put that tube in the V2 slot and it only crackled and popped on the clean channel.  I also tried it in the V3 slot and it popped on both channels but not as loud or as much.  For now I'm just going to get 3 new preamp tubes so I don't have to deal with rebiasing.  I'm off to do some research on tube brands now.  Thanks for all the help everyone.  If you're ever in Wisconsin I'll buy you a beer. :lol:

[Fourth Feline]

The good news is that I understand both the Classic 20 ( which I own ) and the Classic 30 to be self biasing ( cathode biased ). There was certainly a thread on 'The Gear Page '  where a couple of techies mentioned the fact - and that if anything, they ran slightly cool to lengthen output tube life.

I certainly could put any new output pair ( where you have a quad ) into my Classic 20, and it ran sweetly.

My own output valves ( as recommended for more clean headroom by Watford Valves) - where just Sovtek EL34M.

Given that the output tubes are more likely to feel their age, I would be tempted to still research them too, and keep some by for a rainy day.

Whilst you are waiting for the valves, still get some lubricating switch cleaner such as 'Servisol' - for I find Iso-Propyl Alchohol to be relatively inefective on valve pins / sockets.

I still use WD40, - as in my gig bag it doubles as a great guitar string cleaner used in moderation.

[Lazy_McDoesnothing]

That is good news, thanks for that.  I thought one of my amps were self biasing but wasn't sure which one.  I think I'll spring for a whole amp re-tube and keep the ones in there now as spares seeing as It's my main amp simply for portability sake.  

I'll look for the US equivalent of Servisol.  The only places I found to buy it were in the UK.  Found this on stewmac:
http://www.stewmac.com/shop/Electronics,_pickups/Supplies:_Cleaners_and_lubricants/DeoxIT_Pot_and_Switch_Cleaner.html
Seems it'll do the trick.  Cheers!

[Fourth Feline]

That is good news, thanks for that.  I thought one of my amps were self biasing but wasn't sure which one.  I think I'll spring for a whole amp re-tube and keep the ones in there now as spares seeing as It's my main amp simply for portability sake.  

I'll look for the US equivalent of Servisol.  The only places I found to buy it were in the UK.  Found this on stewmac:
http://www.stewmac.com/shop/Electronics,_pickups/Supplies:_Cleaners_and_lubricants/DeoxIT_Pot_and_Switch_Cleaner.html
Seems it'll do the trick.  Cheers!

Bingo !  - that looks ideal . One can will last for yages  - and will also keep your guitar / amp pots running smooth and crackle free.  :D

[Lazy_McDoesnothing]

Cool, thanks for ye wisdom.  Just ordered it and some other random parts that I always seem to find when ordering from stewmac. :shock:

Now if I could just get started on wiring up my warpigs....Say how are you at guitar wiring?  :mrgreen: