Roland JC120 hum

[KarbonHed]

Just been asked by a friend of a friend to have a look at his new (new to him) Jazz Chorus.

The guy who sold it to him said that the slight hum it was producing was a "known thing for these amps". But after a few days of use the new owner thinks that's a a crock, it's just too intrusive.

I've never heard of a hum problem with a JC120 and the way he describes it it sounds like a power supply hum, maybe the big caps going?

So is a constant background hum normal in a JC120? Is it a fault that regularly develops after a while? And if so what is it that fails/ages/whatever?

Won't be getting the amp until Tuesday so if i could be forewarned that would be cool.

Thanks.

[Enzo]

Why don't we wait until you see what it actually is doing rather than us telling fairy tails.

I rarely have to replace caps, more often resoldering is needed than replacement.

Listen to the preamp out and see if it is clean. Plug a shorted plug into the power amp in jack to see if the power amp is hum ffree.

Twiddle the controls, any control that affects the hum is After its source.

[wizard333]

I owned one for years and abused the hell out of it. Even given that, it was whisper quiet, even on 10 with the chorus engaged. Hum is most definitely not normal on those amps.

[KarbonHed]

I owned one for years and abused the hell out of it. Even given that, it was whisper quiet, even on 10 with the chorus engaged. Hum is most definitely not normal on those amps.

That's the reputation I was aware of, clean, loud and clear. I couldn't understand why he bought it with such an obvious bullcrap excuse for hum on a clean amp.

[SPARESROLAND]

Would service notes be any use to you.If you email me spares@roland.co.uk with the part number of one of the pcb's in the unit you have I'll email a pdf to you.
Steve

[Enzo]

Hi Steve, we're glad you have come, you add a direction we don;t generally have covered here. Just a suggestion, look at the posting dates, this thread died four years ago.

[SPARESROLAND]

thanks ENZO

didnt see date just sending answers without really reading to deep into text. Have 100's of emails a day here in Roland / Boss

Cheers
steve

[Alex R]

Nevertheless Steve you are a top man :-)

[soundguruman]

Try grounding the speaker frames.