Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: makingnoise88 on February 05, 2018, 07:03:23 pm

Title: AC 30 reissue hum
Post by: makingnoise88 on February 05, 2018, 07:03:23 pm

Hey guys,
I have a an AC30c2 I’m looking at for a buddy.
It has a pretty hefty hum only when the standby is off. When standby is on it’s quiet as a mouse. The hum changes tone with the depth knob of the trem and will bounce with the trem when changing the speed knob. No other knobs on the whole amp affect it. I’ve chop stocked the amp but with it being a PCB board I’m having a hard time finding anything wrong when using the chop stick! Any idea where to look or what it could be? Thanks in advance!

Title: Re: AC 30 reissue hum
Post by: shooter on February 05, 2018, 07:35:03 pm

Quote

Any idea where to look or what it could be?

Anywhere, that is a complex PITA amps, you have a schematic?, the one I have is to big to post, and if I shrink it you'll go blind :icon_biggrin:

I've fixed 2, both were related to jacks and connectors, I turned down the 3rd.

guessing it still hums with reverb and trem OFF?, also with nothing plugged in?

start with power off and plug in and out 5 or 6 times a 1/4" cord to ALL the 1/4" holes, same with footswitches
power up and see :dontknow:

no love, try again with power off re-seating all the connectors, BE VERY CARFULL because you can be off by 1 pin and that WILL make for a bad day.

suggest to your friend to gut the PCB and build an 'ol sckol AC30 :icon_biggrin:

Title: Re: AC 30 reissue hum
Post by: makingnoise88 on February 05, 2018, 09:11:45 pm

Tried all that with no luck. It’s coming through the speakers. So I’m just not sure.

Title: Re: AC 30 reissue hum
Post by: shooter on February 06, 2018, 08:31:37 am

Pull V1, gone? NO pull V2, gone?, pull V3