Constant Hum in Einstein Combo

  • Thread starter Thread starter PaulyPanacea
  • Start date Start date
PaulyPanacea

PaulyPanacea

Active member
Havent had a chance to sit down & look @ it yet...but this weekend while gigging i was getting a constant hum out of my Einstein. Like a low end hum. couldnt hear it while playing but at idle it was there.
I def know its not cables, pedals, guitars or power..i checked all those.

if its tubes i can replace. could it be anything else before i start getting the hands dirty??
 
Did it still do it after you got back home?

If it does not I would say you were getting some noise from the electricty at the gig. Ground hum if you will. If it does sounds like tubes if you are sure of all the cables/effects/guitar.
 
It wasn't the power. I checked it at home same thing. Guess I better get my work pants on lol.
 
Dang, maybe it is just a pre. Swap some around and see if it helps if you haven't already.
 
Pauly, if it only hums on the high gain (mode MEGA or ch2) then take the amp chassis out, flip chassis upside down so you can see the PCB and adjust the hum trimmer while the amp is in ch2 with gain very high so you can hear the hum. Plug a guitar in and turn guitar volume to ZERO. If nothing is plugged in the amp switches to MUTE and we can't hear anything. Using a small screw driver turn the little white 100 Ohm hum trimmer (on right side of PCB when tone knobs face you) back and forth until you find the lowest hum position.

If that is not helping check the bias of your power tubes. If they run too hot they will hum (before they red plate).

If EL34 do 70-75mA per pair
If 6L6 do 80-85mA per pair
If 6550 do 70-75mA per pair (they need to be biased a bit on the colder side)

If the hum persists replace your power tubes first. For testing any octal type is ok (EL34, 6L6, 6550). Bias them of course.

If it still hums, swap out your preamp tubes. I would swap 1 at a time. Leave amp in standby , swap V1 and wait 30seconds, then turn to RUN and listen for hum. If it still hums, swap V2 and repeat the above procedure. Like that you can catch if it's just 1 tube and just replace that 1.

90% of the time the humming can be taken care of with the above procedure and it is mostly tube related or hum trimmer is off.

If still no luck, please get back.

Good luck, Richard
 
I'm gonna work on it tonight. Hopefully it's just a tube going bad.
 
Pauly,

why don´t send me an email ?

Best,
Peter
 
Thanks for the info, Sir. In this case there is no mercy
and no support from the HQ.

:lol: :LOL:
 
Peter Diezel":t4r1b4zn said:
Thanks for the info, Sir. In this case there is no mercy
and no support from the HQ.

:lol: :LOL:
Click to expand...


Ouch, that hurts. :lol: :LOL:


I would never put any in a Diezel I swear! :yes:

I do have one that already had them in it when I bought it. :D

:lol: :LOL: :lol: :LOL: :lol: :LOL:
 
Papa...didnt want to bother you with something simple... and thanks for ratting me out MOOSEHEADS :scared:

if i cannot figure it out i will def email you Papa.. :salute:
 
Been a little busy this week in studio. I'm gonna do it this week and ill report back.
 
Ok kids...things went south fast.
1. Amp worked w 6550s. Hummed but worked.lt actually hummed w the volume all the way off. And when you tapped on the chassis seemed like it went thru the speaker. Checked all pres w 6550s in amp. All were fine.

2. Changed out 6550 w KT77(new) no more hum but I have no volume at all. I could crank the amp & its barely making noise . What am I missing ?? Tubes are biased to spec. All the pres are good. All connections were good. Guitar is fine.

Any help is much appreciated. I am also emailing this to Papa so he can spank me!!
 
Problem solved. DaMN PI tube. Thanks papa and all you guys for your advise
 
Good to hear it was a "easy" fix!

Let us know how the KT77's treat you. :thumbsup:
 
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