80's Roland JC-120 2 questions

[bobkeys]

Hi All, thanks in advance for sharing with me.
I picked up an older Roland JC-120. Its kinda beat up bu still working. The low input jack in channel 2 appears missing so I called the previous owner and he said its inside, that the nut came loose and now the jack is inside.... So question 1) How can I open up the JC-120 to get at the jack and reconnect it? Is there anything I need to watch out for, like is there anything I could erroniously brake?

2nd question; there's a little noise like a combination hiss and hum, not loud, in fact not bad at all, very tollerable, but is this normal or should these amps be completely noiseless?

Thanks
Bob

[52 Bill]

Hey Bob, welcome to the place.

There are no such things as totally noiseless amps. The JC-120 should not be really noisy at idle, but there will be some hiss and hum there.

As for removing the chassis, you first need to remove the upper back panel. Then the head will be held into place with screws on the top and on the sides of the amp. These usually are black phillips head screws, with a head size of about 3/8". Be sure the amp is unplugged from the wall outlet.

Before you remove the screws, you will need to loosen the speaker wiring bundle. Normally the wire is bundled together and twist tied to the baffle board.

When the screws are removed, the chassis will slide out the back of the cabinet. The input jacks are wired together by a wire, so the second jack should be just inside the front panel. Be sure to check the inside of the chassis for any loose washers that might have fallen off of the jack when it was pushed inside the amp. These washers can short out things inside the chassis if they happen to land in the wrong spots.

Roland used a number of different style jacks on these amps, so finding the correct replacement nut may be a problem. In fact you may want to put off the project until you already have a replacement nut in hand.

[bobkeys]

Hi Bill,


Thanks. Now I know what to expect. Sounds simple enough to pull out the chassis. Thanks again. The nut to hold the jack in place appears to be the usual flat nut. I'd gladly use one from channel 1 as I don't use that channel.

Bob

[Ronsonic]

Sadly, the Roland jacks use a satan-sized nut that you'll need to order from them. The good news is they have them and will sell them. The bad news is that they are profoundly non-cheap. You may also find that yours are one of a series that were defective and will begin dropping like flies.

[Gtr_tech]

I'd just replace the fricken jack then....