Roland jc50 advice needed!

[Christophe]

Hi everyone, and best wishes for 2017!
Sorry, this is a minor thread, but I need your input on that, and I'm sure that at least one of you can help!
I've just bought a Roland jc50, being in love with that amp, since I've been using one for years at a friend's recording studio. The one I bought is older, and there's a background hum/white noise when I turn it on, even with no guitar plugged into it.
Now, I know early JC's are famous for background noise, and that they were meant to be played loud live, so hum is not an issue, etc...
Still, the one my friend has is quite silent, silent enough to use it in the studio.
So maybe this noise issue was improved other the years of production. And maybe there's a mod that can be made to reduce/get rid of this background noise?
Has any of you done that already? Or could you recomment a specialist, a Roland wizard who knows these amps backwards, and knows how to fix that?
Any thoughts welcome, thanks!

[rfurtkamp]

I have a very early JC50 myself.

Is the three way deathswitch still installed?

Try going up/down to do ground lift if so.

Past that, it *is* almost 40 years old at this point, could probably use some look at the electronics if it's making noise that you're not happy with.

As far as guys to work on them, honestly not sure. There aren't as many SS wizards out there.

[Christophe]

Thanks man. 3 way deathswitch? All I see are the standard power/brilliance/chorus switches. No switches on the rear panel. I have an European version.
I guess I'll just take it to the repair shop...

[rfurtkamp]

Polarity on the power switch. It'll have a center detent for off and turn on whether you flip it up or down to reverse the ground.

[Christophe]

Oh, ok. Turning it up or down brings no change... Maybe that's what needs repair...

[rfurtkamp]

It won't eliminate noise, but can eliminate ground hum at the price of being, well, possibly not in line with the rest of what you're using.

In the old days, it wasn't uncommon to get shocked from a mic and an amp being out of polarity if playing a guitar and singing, etc.

The deathswitch was to allow you to not eat voltage! It's not safe by modern standards, but...

As it stands, I'd have to hear the amp to gauge whether it's within the normal realm of background noise.

[Christophe]

The amount of noise doesn't really increase with volume. Or just slightly. It's totally reasonable, it's just more than the other jc50 I know... I could send you a vid, but it would be biased by the room I'm in, the sound of the recording machine etc... I'll have it checked when I can...

[rfurtkamp]

Did you try that JC50 in the same room with the same gear he's using?

I.E. power, cables, effects, guitar shielding?

[Christophe]

Yeah, that would be the ultimate test. Remains to be done...