Roland Jazz Chorus77 static from low E string only?

[Galen]

Hi

I have a Roland JC77 that I play with an acoustic guitar that has an Seymour Duncan sound-hole pickup.

Lately their is a static type sound when I hit the low E string, but not on the other strings.

I found I can also produce the static sound by slightly shaking the amp.

The sound is not a continuous humm...it is a raspy, crackly sound that starts and stops.

I was told it could be a lose screw or connection and its rattling is being amplified. I have checked all the external connections but have not found anything.

Any suggestions for tracking down and fixing it.

Is it very complicated to open up the chassis to see if there is something loose there?

Appreciate any insights.

Thanks

Galen

[Enzo]

SHaking the amp triggers it? There is your clue, there is a loose connection of some sort. Your E string simply resonates in the cab to vibrate the chassis the most compared to other notes.

I use the ball up your fist and whack it approach myself.

COUld be an electrical connection - loose wire, loose connector, cracked solder. COUld be something mechanical - loose mounting screw on a transformer or on a control or jack nut. Only way to sort it out is the have the amp open and running, and probe around with something insulated, like a wooden chopstick, looking for what reacts to the touch.

[soundguruman]

Generally, resolder the circuit board.

[Galen]

Thanks

Only way to sort it out is the have the amp open and running, and probe around with something insulated, like a wooden chopstick, looking for what reacts to the touch.

Thanks for responding...I have looked around online, but have not been able to find any info on how to open up the amp to get to the chassis...and it is not straightforward just looking at it.

There are four screws on the top of the amp where the handle is...I assume that backing them out would allow me to slide the chassis out from the back side of the amp.

Any idea where I can find out how to take apart the amp...or is that just too complicated without proper tools and know how?

Thanks again

Galen

[Galen]

Thanks soundguru..do you know of a site that explains how to get at the circuit board?....it is not straightforward how to get inside the amp, just looking at it.

[Tonewood]

Thanks soundguru..do you know of a site that explains how to get at the circuit board?....it is not straightforward how to get inside the amp, just looking at it.

I have a JC120. It has 2 screws on top & 2 on each side that hold it in. If your board looks anything like mine, re-soldering the whole thing will be ugly. I would be sure to chopstick first & try to narrow it down. May want clean & check the pots while you are in there. My 120 was rattling on one note & it turned out to be a loose volume pot. I guess it wiggled on the bad note. Tightened it & cleaned it and its connections at the board and all is fine.

[soundguruman]

take all the knobs off, take all the nuts that hold the controls off, take the jack nuts off, take the screws that hold the circuit board out.
Pull back the board, flip the board over.
As a precaution use an anti static soldering station. There are a few parts in there that can be fried by static electricity, as I recall.
As it was said- the most common place to have a cracked connection is the controls, or the input jacks. But it could be anywhere.
If you have never done this, you might want to find yourself a good amp tech.
Occasionally this same type of problem is caused by dirt or oxide on the jacks. The jack has switches inside that need cleaning. The most common place is the effects send/ return jacks, etc...power amp in jack. By putting a patch cord between send and return, you bypass the jack switches.

[Galen]

thanks soundguru...I called an amp tech and he estimated $90...and he'd have it a week. I have an important solo gig I need it for sooner...so I re-read your suggestion and now understanding there is a nut accessible under each knob, I thought I would at least check that out. Turned the amp on and zeroed in on the hi-treble knob as the source of the static...pulled the knob, and sure enough, the nut was way loose. I tightened it down and....NO STATIC!! And then pulled all the knobs and there were 3 more nuts that needed tightening.

$90 is a small fortune right now...so to have saved it is a huge help..I so appreciate the support here!

Galen
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