Roland JC-120 static

[yyyames]

Got an older JC-120 recently everything seems to be in great working shape except for some annoying static when I turn the amp on. I see videos of other Jc-120's that sound virtually silent. Is this normal or can I do something to reduce the static?

[Jazz P Bass]

That static sound can come from any number of circuits in the amplifier.
What is a tried a true approach, is to try and narrow down the problem.
(Divide To Conquer)
Is the noise there with and/ or without an instrument plugged in.
Do any panel controls effect the noise.
If so, which ones.
By using the send & return jacks on the rear, you can narrow down whether it is a preamp problem (send out to another amp sounds good or bad) or a power amp problem (return sounds good or bad)
Generally speaking, there is not a chart anywhere that will narrow down a symptom to a known cause.
The problem has to be investigated.
This is what a tech would do.

[yyyames]

That static sound can come from any number of circuits in the amplifier.
What is a tried a true approach, is to try and narrow down the problem.
(Divide To Conquer)
Is the noise there with and/ or without an instrument plugged in.
Do any panel controls effect the noise.
If so, which ones.
By using the send & return jacks on the rear, you can narrow down whether it is a preamp problem (send out to another amp sounds good or bad) or a power amp problem (return sounds good or bad)
Generally speaking, there is not a chart anywhere that will narrow down a symptom to a known cause.
The problem has to be investigated.
This is what a tech would do.

The static occurs is when the amp it turned on, nothing plugged in and raising the volume off zero. The static level doesn't increase whatever level you are on. None of the controls increase or decrease the static. When testing the outputs on the back the static all but disappeared when plugged into the L return ( mono ) channel. What does that mean I need to fix?

[Jazz P Bass]

So the volume control at zero (off) gets rid of the static?
If so, then the problem is before the volume control.
That narrows down the problem considerably to the preamp.
I do not know which model you have .
It appears to be the "E" series.
http://media.rolandus.com/manuals/JC-120E_OM.pdf
Someone is going to have to come up with a schematic.
This one I do not have.
You could call Roland.
If nothing else, the main voltages should be checked for stability & lack of ripple.

[yyyames]

So the volume control at zero (off) gets rid of the static?
If so, then the problem is before the volume control.
That narrows down the problem considerably to the preamp.
I do not know which model you have .
It appears to be the "E" series.
http://media.rolandus.com/manuals/JC-120E_OM.pdf
Someone is going to have to come up with a schematic.
This one I do not have.
You could call Roland.
If nothing else, the main voltages should be checked for stability & lack of ripple.

thats my amp, Im not tech savvy with amps like going into one to repair a problem. Its cool I know kinda whats going on but would really like to fix this practicing is getting really annoying lately.