#1
Edit: Issue resolved! It was a grounding issue- some nuts weren't tight enough.

Last night I did my first electrical mod for my peavey valveking (see the mesa mod here http://ultimate-guitar-valveking.wikispaces.com/Amp+Mods+-+Electronics).

edit: here is the mod

Remove R122 (no jumper needed).
Leave R124 in place (Don't touch it).
R116 to 10k (Wattage don't matter here).(10K has more gain, 22K has less... tightness of tone depends on EQ and setup)

The tone stack cap & resistor are crutial to Mesa sound;
C2 to 470pF
R4 to 47k

At the very least, it turned on, so I'm glad for that.

But now my amp has a loud constant hum on BOTH channels. It has a signal from a cable through both jacks (I'm not 100% that the clean channel has signal as I've been in my garage- no guitar.)

Plugged my guitar in and:
1) Both channels have signals, they are just very noisy. The hum increases in volume as I turn up the amp volume. The hum is present even when both volumes are OFF. There is also an occasional soft pop on either channel, no success in producing it myself, though.

2) This is weird: touching certain parts of the amp- the power switch, standby switch, or the jewel knob (?!?) kills most (but not all) of the hum, but I can still hear the guitar. Sounds like a grounding issue? Any advice on diagnosing this further?

I'm going to go back in and look for

1) cold joints/excess solder.
2) One of the pads that I was soldering began falling apart as I soldered. I was able to salvage it but I'm betting that is my main issue. To fix this i would bypass the pad and link it to (either with wire or directly) the next component in the circuit, correct?
3) Try it on a different outlet to rule out ground loops (haven't used it on this outlet before).

Anything else I might have overlooked?
Last edited by Sadistic sponge at May 26, 2013,
#2
Since the hum stops when you touch certain parts, I assume it's a grounding issue, but there might be other things wrong as well... Wait for what other people say
"Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."
-Douglas Adams
#3
Can you post a better link? It asks for an account. Can you copy paste it?
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#4
Quote by R45VT
Can you post a better link? It asks for an account. Can you copy paste it?


Here is the mod, sorry!

MESA mod

Remove R122 (no jumper needed).
Leave R124 in place (Don't touch it).
R116 to 10k (Wattage don't matter here).(10K has more gain, 22K has less... tightness of tone depends on EQ and setup)

The tone stack cap & resistor are crutial to Mesa sound;
C2 to 470pF
R4 to 47k

Edit: I'm a dumbass- i figured it out. Some of the nuts on the control knobs were not screwed in all the way, causing grounding issues. Tightening them fixed it. The rest of the noise was from a ground loop in my garage- went away in my room. Also, this mod sounds kickass!
Last edited by Sadistic sponge at May 26, 2013,