Roland Jupiter 6 - calibration tips

The Jupiter 6 is one of Roland’s two most beloved 80’s polysynths, the other being the Jupiter 8. While I was looking for service documents for the Jupiter 6 though, I came across some absurdly aggressive forum posts from people who don’t like this synth and are pointlessly mad that a lot of other people like it a lot.

“Anyone who buys this synth is an idiot. It sucks your ugly fat mother’s balls and is only worth $100. You’re better off saving $6000 more and buying a Jupiter 8.” I like this synth, and I really don’t like the nasty and condescending vibes frequently given off by many (not all!) members of the online synth community, and its incessant undercurrent of crude misogyny. Maybe people (men) who frequent forums like Gearslutz (probably the worst) and Muffwiggler and CDM don’t notice this trend, because they definitely get super defensive and even counterproductively aggressive when anyone tries to mention it. Amazingly, people often try to deny that it happens at all. But as a woman in a subculture dominated by men, I notice it all the time and it always makes me cringe. On Synthesizer Freaks on Facebook, I once saw someone who tried to bring it up (and his supporters) get hit with a torrent of sexist and homophobic insults, mixed with obviously-implausible denials, from dozens of people… and then a moderator deleted the whole thread. I’m not going to use my synth repair blog to tell you all what to do, I’m just asking you to think about what you do.

Anyway.

Service Tips: This one had a SN in the 360000s and its module board was quite different from what was shown in the service manual available online. This was especially important when it came time to calibrate it. Here are some notes on test points and trimmer locations for this production model:

• When you are doing filter calibrations, use the test point on the upper left corner of the module board that is labeled “OUT.” It works much better than using the main output as the service manual for the other versions suggests; the main output seems to have a lot of supersonic noise on it that will make it hard to read the scope.
• This version has two resonance trimmers (instead of one in the previous version) that are used to adjust the X and Y offsets of the resonance curve; the Y is the one closer to the back of the synth, the X is just a couple inches below, both on the module board.
• Use test points 2A and 2B for pulse waveform adjustments. They will be almost impossible to do from the output, as the manual once again suggests.
• A lot of the voices’ circuitry are kind of dual versions (so hard-synced in pairs) in this version so there are only half as many trimmers for certain parameters, or even fewer for some things.
• Also, I saw several posts from people saying that they were reading voltages like 3-4V on the DA offset test points (where it should be very close to 0 V) even though everything else seemed to be working normally. I will admit that the reason I was reading these posts is that I myself was briefly confused. But the DA offset test points will not read 0V until you switch the synth over to test mode by moving the tiny switch on the center of the left edge of the CPU board to the “Jig” position, and THEN load program A1. They do NOT read 0V normally.

Work Done: Just maintenance and calibration for the most part. Replaced PSU capacitors, heat sink compound, Roland power inlet replaced with IEC inlet, new patch memory battery. Found one bad diode messing up patch bank switching matrix. Calibrated to Roland’s specs.