Tube amp help! (Valbee humming)

[Reth]

My amp hums! Yep. It's a Valbee. 3 pin, so no grounding issues here. Humming can be picked up with mic.
There was no humming before the accident, now hums without guitar input.
Tubes are Chinese-made, 12AX7 and 6l6GC.

Okay, here's the story and suspected cause of humming:
While the amp was on and playing, the power cable of the amp socket came out a little, cutting off the power and sound.
Seeing/ hearing that the power was out, I immedietly pushed back the cable (natural reaction hee).
Power and sound returned, "pop" sound heard. Then I turned it off the normal way..
So basically it was like a "power trip"- a cut off in electricity to the amp while its on.

Yeah. I think something must've gotten messed up during that accident. Tubes I suspect.
I've tried a test checking for hum with and without the preamp tube, just some advice from JE.
It involved plugging out the preamp tube and maxing the volume, then compared with preamp tube plugged in:

Without 12AX7 (plugged out):
-There is a subtle humming upon turning on the standby switch. *hmmmm*
-Humming remains the same upon increasing of volume/gain knob
-Also remains the same when distortion switch is activated

With 12AX7 (plugged back):
-A little louder humming upon turning on standby switch
-Humming volume incraese upon maxing volume knob
-Humming increases in "hum-ness" or harshness upon maxing gain(clean) knob.
-Upon activating distortion switch, hum becomes "gisshh-ish", however my amp's distortion is naturally "gisshh-ish"/ british-voiced.
Just take note that humming becomes very evident with distortion engaged.

I suspect either the tubes or other components had been damaged from the accident..
Now I dunno what to do.. Any help or advice would be greatly appreciated!

Thanks! :wink: sorry for the long post, I just wanna get the details through yeah

 

[Indigo_blues]

wah, sounds like could be anything man. 8O

The 'pop' sound you heard was a power surge.. could have done bad things..

 

[re_unknown]

sheesh...
lucky was only POP, not BOOOM!

 

[Reth]

oh man.. 8O

Is it normal for tube amps to hum in the first place? help help

 

[suckasucks]

try changing your tubes. how old is the amp?

 

[Reth]

my amp is only 6 months old.. change both of them??

 

[JE]

reth: question: did the amp hum (as much) before the incident?

i wouldn't be too concerned with the pop.. try on any amps: switch it off and on (immediately) you will hear a pop.

like re_unknown said.. it's more likely to boom than pop if something blows up.

 

[JE]

reth: try pluggin ur guitar into a good(working w/o hum) effect (a drive pedal will do) and into the effect return loop. turn up the level knob of ur effect. do you still have loud hum?

 

[blues_freak]

try puting a big capacitor at power supply section, 100uf/400v it should reduce the 60 cycle hum(or 50 cycle)

 

[suckasucks]

well if you havent changed the tubes(stock) i think you should, since SL prob kept the amp for awhile and people probably have tried it before you. never know whether they handle the amps well.

 

[Indigo_blues]

6 months still under warranty right? Just bring it back to Swee Lee lor..

 

[Reth]

JE; not I don't think it hummed before the incident. Tried what you said- it still has that a soft hum.. not loud.

blues_freak; hehe, you lost me there

My amp was brand new, it came from an un-opened box. You sure warrenty covers this?? Its sorta my fault..

 

[JE]

okay.. so we pretty much isolate the hum to the power section.

now you can try changing the 6l6. if it still does not work, then it should be the power capacitor and diodes.

 

[Reth]

hmm okay. most probably its the tubes??
with the preamp bypassed, there is still hum, but with the preamp and preamp tube got more hum..

 

[Reth]

:smt086

 

[re_unknown]

ahh, u want to cover it SW warranty also no need say so loud that ur fault XD
just say it dropped down the shelve before hitting the chair then onto the ground with a THUD, then u were so shocked that u spilt the can of coke u were holding and sparks flew out together with the humming sound!

sure can get warrantly liketat XD
jkjk