Roland JC-120 Jazz Chorus Amplifier Repair

Roland JC-120 Jazz Chorus
Roland JC-120 Jazz Chorus

The other day I picked up a classic Roland Amplifier called the Roland JC-120 Jazz Chorus. I have been on the lookout for a used version of this amp as they can get quite pricey brand new. I found this JC-120 for $125 at the local used music shop in Nagano-city, JAPAN. The serial number indicates it is a 1996 model JC-120U. Brand new these run about $1100 in Japan.

Previously I had found only two used Roland JC-120’s in Nagano on two other occasions. On one of those occasions, the JC-120 had a really bad static sound coming out of the speakers. I thought it might be the distortion, but that was already turned off, so I thought the speakers might have had a problem. The asking price was $500 for the amp and I felt that was a little too high if indeed it had a speaker problem. The second opportunity I had to buy a used Roland JC-120 was about two years later. This time everything worked and the price was $450. I decided to wait and come back the next morning. Unfortunately later that day, another guy came in and bought the JC-120 so I was out of luck. Then, finally a third chance came a few days ago and I decided to not let it go.

The reason for the amp being sold for so cheap was mainly because the staff didn’t really know much about the Roland JC-120. It had several scratchy pots which crackled quite noisily when turning the knobs. They thought this warranted the amp being thrown into the junk bin and sold for cheap.

If you check out other amps in stock at the used shop, you’ll notice they price their Fender and Marshall amps very high. They tend to sell well in Japan. The Roland JC-120 sells well to studios and practice rooms that are rented out. I have also found that most venues that I’ve watched live performances at usually have one Roland JC-120 available. The fact that you don’t hardly ever see them on the used market in Japan also suggests people hold on to them.

For me, I’ve always had an interest in the Roland JC-120 because it’s a very clean sounding amp and I love the chorus in it. I also know it works well with keyboards, especially with the Rhodes and other electric pianos. As a young kid learning the guitar in the 80’s, I grew up listening to a lot of Jazz and 80’s chorus type pop songs. whether the JC-120 was used much in the 80’s I’m not sure, but it definitely gets me the sounds I like so it’s pretty cool to finally have one.

After opening up the JC-120, I managed to completely fix the scratchy pots by shooting Deoxit in and around the pots. I had to take out the electronics bay from the chassis to access the components, but it wasn’t too difficult. The distortion works but it sucks if you use it for distortion as it’s not really that great. I actually like to turn it on and use it for kind of a volume boost, plus it grunges up the clean sound a tiny bit which can be a nice effect for some songs. The Vibrato and Chorus both sound absolutely beautiful.

Now the one area that doesn’t sound like it’s working is the Reverb. It might be working and if so, it’s quite subtle. I didn’t see anything wrong with the Reverb Tank inside, but I may open up the amp again to check. Perhaps if anyone who owns a Roland JC-120 and has a working Reverb could let me know if it’s indeed a noticeable or subtle effect. The distortion on the other hand is way too subtle for most people which is why I think most hate it. I suppose if I had any sort of problem with the JC-120 it could be the Reverb.

Another area that can be a negative aspect of the JC-120 is the loud “hiss” that this amp can generate. On mine it’s there but it’s not too loud. I definitely don’t notice it when I play and I suppose a proper noise gate running through the effects loop would take out that hiss no problem. I can understand how some people would be annoyed by it, but frankly I find most amps I’ve used to have some sort of hiss, buzz, or other crazy sound coming out of it.

Overall, I find the Roland JC-120 to be a very nice sounding amp. I’m very happy with it when playing either a guitar or keyboard through it.

Below is a video on Youtube of someone cleaning their Roland JC-120. I found the info very interesting.

3 thoughts on “Roland JC-120 Jazz Chorus Amplifier Repair

  1. Bobby Voltage

    I just had the reverb go out on my JC120 and was wondering how hard it is to fix. It is not a subtle effect in the least. It is as valuable and iconic to the amp as the reverb. I started a 6 week tour a few months ago and the reverb went out on the second day. I was really disappointed. Anyway, still haven’t found an easy way to fix it and don’t want to take it to just “anyone”.

    1. Bill Smallacombe

      I would start by cleaning and carefully re-seating the molex connectors. There are also to RCA/phono type connectors for the input and output of the reverb tank. Clean those as well.

      1. The good thing is tanks are cheap. I have replaced three different tanks in three different amps and one was simply a reverb upgrade. If you check out https://www.amplifiedparts.com/tech-corner/accutronics-products-and-specifications you’ll find that most tanks are under 30$. One of my amps, a fender hot rod had reverb drop outs and I did a ton of research into the possible failing components. And after changing a bunch only to realize the tank input was failing. And on my Roland Jazz Chorus 77 one of the springs had come unsoldered. Now it sounds better then ever! So in both cases it was the spring tank. On another amp I put in a three spring long tank to get more reverb. Now if I could just resolve my JC-77 static noise issue I’d be happy. Good luck!

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