60 hz hum coming from amp

[taxistationary]

Re: 60 hz hum coming from amp

Well, it's not any of the caps you tested then. If it was, instead of having a reading of zero on one side, you'de have more, meening DC leak past the that cap. I really don't know that much about SS amps. You mught want to check the transistors, but I really can't tell you how too, sorry. One thing to keep in mind, regardless of what anyone says, I think your always going to get a humming sound from a SS amp more-so you would from a tube amp. Trasistors are just noisey. Esspecially since you say that as you turn up the gain it gets worse. The transistors are pretty much where all your satuartion comes from. Good luck, I hope that helped...

[jgcable]

Re: 60 hz hum coming from amp

The hum is so loud the gain channel is unusable. The clean channels is completely silent. The hum increase if I turn either the gain or the volume up on the gain channel.
I have all the boards out of the amp currently. The hum sounds like a ground problem but I checked them all. I wish I knew more about this stuff.

[Twisteramps]

Re: 60 hz hum coming from amp

JG - those leds are clipping diodes I'd wager.

Pete

[Deneb]

Re: 60 hz hum coming from amp

Bad hum, worse as the gain is turned up. As John said, your cap readings are good. All the caps are doing their job.

Could be a fucked up power supply. Maybe the reason you don't hear it in the clean channel, is from a lack of gain.

Imagine having a guitar with the pickups wired retarded. You don't hear the hum on clean, but when you crank the gain, it amplifies the problem.

[Newc]

Re: 60 hz hum coming from amp

The hum is loud enough that the gain channel is unuseable!?
Could it be a switching disorder (as in the switch is either bad or it's lifting the ground as well)?

[Deneb]

Re: 60 hz hum coming from amp

I just have to say...

I bet you feel like an asshole getting rid of the JCM800 now... It was problem free, and sounded awesome.

[jgcable]

Re: 60 hz hum coming from amp

[ QUOTE ]
I just have to say...

I bet you feel like an asshole getting rid of the JCM800 now... It was problem free, and sounded awesome.

[/ QUOTE ]

I would feel like an "asshole" if I didn't also have:
Modded Carvin MTS3200 head that sounds like a cross between a rectifier and a 5150
Laney PL100 head that absolutely kills. Fantastic gain, great clean channel and tons of options.
A Fender Ultimate Chorus coming in for repair and a bunch of excellent speaker enclosures.
I also have access anytime I want to a Vetta 2 head and a 1st gen Dual Rectifier.
So.. to respond to your post Deneb.. nah.. I don't feel like an asshole at all. That JCM800 certainly did rock though!!!! [img]/images/graemlins/toast.gif[/img]

[Whiplash]

Re: 60 hz hum coming from amp

I would re-check the grounding and power supply on the amp. Im doing an audio engineering course, and sometimes when using tracks recorded in the USA, there would often be a 60hz hum resultant from the USA mains supply on the track. We would then just cut out that frequency.

It could just be a coincidence that its a 60Hz hum, and thats what your mains supply generates, but worth checking out anyway i think.

[jgcable]

Re: 60 hz hum coming from amp

Are you talking about the single gigantic transformer that is in it? How do I check that and what do I check it for. It is frikkin huge. In my past experience, if a transformer like this one went bad it would always smell. This one smells and looks perfect (and the clean channel is 100% perfect). When I switch from channel 1 (clean) to channel 2 (distortion) the 60hz hum comes on. This isn't some background 60 hz hum. This is series. Anything over 3 on the volume or gain on channel 2 makes the amp unusable do to the loud 60 cycle hum.

[Deneb]

Re: 60 hz hum coming from amp

JG, you're all talk. I know how you feel about that amp, because I feel that way about it sometimes...but it's all cooled by what I have now [img]/images/graemlins/smile.gif[/img]

[jgcable]

Re: 60 hz hum coming from amp

[ QUOTE ]
JG, you're all talk. I know how you feel about that amp, because I feel that way about it sometimes...but it's all cooled by what I have now [img]/images/graemlins/smile.gif[/img]

[/ QUOTE ] [img]/images/graemlins/toast.gif[/img]

[Whiplash]

Re: 60 hz hum coming from amp

Honestly i wouldnt know what to check, I know very little if nothing about electrical and electronics stuff, i would just take it to a techy mate and see if he could work it out. Maybe the beating means that the circuitry has been grounded twice somehow, but i'm only guessing from here on.

[DeathDaily]

Re: 60 hz hum coming from amp

[ QUOTE ]
The hum is loud enough that the gain channel is unuseable!?
Could it be a switching disorder (as in the switch is either bad or it's lifting the ground as well)?

[/ QUOTE ]
Is the switching malfunctioning? I have an old rg120es that's doing what sounds like the same thing and the switching doesn't work. If you find a fix, please post it. Might help me too!