What's Wrong with this Amp?

[BlueSparkle]

It's common for the amp to lose a channel, or to lose the chorus (loss of channel)
channel 1 is more common for some reason, almost as if there is a signal balance difference.

any hard knocks to the rear can damage the output drivers (they're TO3's mounted to the back, not uncommon to see them with big dents in the cap, usually means they've taken punishment.

Age is the main killer, most of the survivors need all the electrolytics replaced, and there are a LOT of them, all glued down on the PCB.

If you give it to your amp tech, he/she can do the work, but it's likely to cost about a ⅓ of the cost of a brand new JC120.

But - The new ones do not sound the same. They are quite a bit noisier in my experience.
There are about 5 or 6 PCB revisions, and there are a few variants on some of those - so the serial number is crucial when trying to identify the circuit and match it to the schematic. Not only that, but sometimes it's absolutely necessary to remove the PCB's from the tray just to identify which particular board revision it is - some are silkscreened differently, some have no screen - etc and believe it or not, this is key to identifying which exact board and circuit variation you have.
Roland are pretty good about all of this though - they do have all of the information in their schematics and the identifying descriptors in the service manuals.

[Unicorn Warrior]

The seller is doing the honorable thing and is giving me a full refund + shipping. Very thankful for that.

[filthypit]

Been playing them since early 80's - They're awesome amps - but can be VERY finicky.
Also, its a BIG fragile piece of equipment so I'd worry abt inadequate or improper packing. My current JC120 doesn't leave the house because I don't wanna replace it (again). All the diff elec components make it a nightmare to work on.

I still plan to source another one. I'm just very fond of their sound. What sort of problems have you had over the years?

Reverb tank died on one after hard knock. On/off switch on another & finicky switches w/ age. Speaker gets brittle (after 30yrs in the swamp). Probably not anymore than any brand of amp ...with a zillion options. Repair shops get nervous when ya drag one in, so that's telling.
This is my choice in amps, so Ive dealt with it. Nothing comes close for the money.

[BlueSparkle]

The only things i cant get hold of are some of the early toshi transistors, the 7122 and mn3002.bbd.
Subs exist for most other stuff but the circuit resistor values need tightening up on some of the preamp stage drivers when new replacements are subbed.
Fiddly, yes - if you want it fixed properly, i.e. to rolands original spec.

Pioneer made the original speaker so you can re-cone them

[Unicorn Warrior]

Got a new one coming. The old one had problems, but did seem to intermittently at times perform unhindered. From that, I feel as though I gathered enough from it to do a sonic comparison.

Will weigh in my thoughts when the new one comes