Crate GFX 120 Hum problem...

[Zip]

Just got the above amph today. The guy I got it from said the hum (quite loud & annoying) was there when he got it from the original owner.

When I turn the unit on, there's a loud hum - like a 60-cycle, sort of. It remains constant...volume pot doesn't increase the noise, channels don't make a difference. Nothing I do changes the volume/pitch of the hum. It's just there. Removed the chassis from the amph, and all wiring/etc. looks original & intact. I certainly don't mind jumping in this thing, and I have the schematics - I just don't know how to proceed to troubleshoot this.

Any thoughts or ideas (aside from comments on solid state & Crate being complete rubbish oke )??

 

[kiteman]

Check the caps on the power supply. They'll be on the DC side after the rectifier.

 

[Commodore 64]

I have a Crate GTX212. I bought it used, and the power supply had been replaced. It might be a common thing. Look for bulging caps as stated above, it might be a simple fix.

 

[Zip]

Yep - it was the filter caps. One read about 47, the other about 32. Replaced them both, and now I get screaming solos out of this amph :happy

Edit - I lied. It's a GFX 212.

 

[Commodore 64]

Yeah, so is mine. Mine's in the basement though, resting...I don't have enough room upstairs for it.

 

[Zip]

I got this thing for 60 bucks - the two 12" Eminence speakers are worth that alone. So it's all good.

 

[kiteman]

Good job.

I had a Crate G212. Notice I said "G212", it was long long ago.

 

[Commodore 64]

Hmm I paid 75 for mine, but I don't think mine has Eminence Speakers in it...I'll have to go look when I get home tonight.

 

[Zip]

The label says "Crate Custom Design"......they're rebadged Eminence speakers

 

[Commodore 64]

OK, I just went downstairs to check. My amp is a Crate GT212, with the Crate Custom Design speakers. It has a spring reverb tank. Date on the speakers says 2001.

I do wish my Blackheart had reverb.