Roland Jx-8p, one voice louder than others

[burymyteeth]

Hi there,

I recently purchased a Roland Jx-8p and it has a funny issue where certain keys are about twice as loud as the others.It will be the same two keys on every octave, but also shifts around. So the interval between the two notes is the same, but if I run down the key bed and then start over from the top, the two notes will change but the interval will be the same. I've already noticed that the aftertouch seems to be a common issue with these, and it currently isn't working. Not sure if this is related though because you can select if you want the aftertouch to affect volume, brilliance, or vibrato, and the issue is always louder volume no matter which effect you select.

Just got it out of the box yesterday and have had it sitting powered on for many hours, thinking it maybe needed to settle or something. Any advice on how to troubleshoot this is greatly appreciated, thank you!

[chrisakaneelix]

Hi. That sounds like the individual voices, which is common. Do the louder notes sound "brighter" or just louder? Unfortunately, as far as I know, you would have to have individual chips replaced for the two voices that are finicky. It's common (and they all go through it). Just have to pinpoint if it's the filter or amplifier that's doing it...

[burymyteeth]

Hey Chris, thanks for your reply. I think the notes are just louder, not brighter. The interesting thing about it though is that the notes that are louder change every time I run down a scale, so, do you still think its the individual voices? Here is a recording of whats going on. Probably the most annoying thing I've recored in my life. Thanks!

http://s000.tinyupload.com/?file_id=260 ... 8875662643

[atkbg]

Disclaimer: Not an expert

If its only a few notes (ie: middle c, A# 4th octave, etc) its sounds like a contact strip. Basically, no velocity, note on off only.

But, again, no expert here.

[burymyteeth]

Hmm, thanks, you might be on to something with the no velocity, note on and off only. The strange thing is how it drifts around the keyboard, not staying on any particular notes. The only consistency is that its two notes per octave, with same interval between them, but will drift around to different keys, if that makes sense.

[atkbg]

Than it sounds like a chip, not a contact. If it was a contact, it would happen on the same note every time.

[burymyteeth]

Ok, on further pondering the issue occurs every 6 notes. The Jx-8p has 6 voices. This synth has a test mode that helps you identify problems with the voices. When I get home this evening i'll put it into the test mode and be able to identify which voice it is out of A - F. So, this is where I really expose how little I know... I'm used to looking at tube amp schematics, you put even a block diagram in front of me for this thing and I'm totally lost. If we're talking about 1 voice out of 6 being "bad" in the sense that it doesn't seem to be shaped by any type of filter and is just straight signal, can anyone help me narrow it down from there? Perhaps indicating where the "voices" even are on this block diagram? Thanks so much for your time.



http://www.synfo.nl/servicemanuals/Rola ... _NOTES.pdf

[Mooger5]

In the diagram and the schematic the individual voices are represented inside layered dashed rectangles. Where it says "Synthesizer Module (A-F)". As all six voices are identical, only one is actually drawn, to save space.

It could be just one voice that probably needs to be calibrated. Same interval, twice per octave, yep just one voice. But I´m not familiar with the JX-8P.

[burymyteeth]

Ok i see them now. I'm just talking to myself now. But hoping someone will come along that knows about this issue haha.

[burymyteeth]

In the diagram and the schematic the individual voices are represented inside layered dashed rectangles. Where it says "Synthesizer Module (A-F)". As all six voices are identical, only one is actually drawn, to save space.

It could be just one voice that probably needs to be calibrated. Same interval, twice per octave, yep just one voice. But I´m not familiar with the JX-8P.

Sorry Mooger could have refreshed before my last post, thank you!

[Mooger5]

No problem. Wow, the calibration seems very simple, according to what´s on page 5. Just one trimmer per voice.

[burymyteeth]

Yes it sounds pretty basic, pretty awesome.

[Mooger5]

Yeah and to make things easier the only test point is directly connected to the output jack so there´s no need for an oscilloscope to monitor the amplitudes; just connect the output to your soundcard and use an online scope, or just trust your ears and your DAW´s VU meter. Or, just use the DAW to visualize the test waves.

The trimmers still have to be adjusted but to make sure right away it´s just one voice that needs to be calibrated (though it´s best to calibrate them all), just do the following test:
Say it´s the 6th voice (Synthesizer Module F) that sounds louder. As the assigner scrolls through all six voices sequentially, if you start by pressing a C key, then C#, then D, then D# and so on, the F key will sound louder, then going on, and six semitones later the B note will sound louder too, as it´s the same voice, then moving on the next note will be an F key again and so on. Six voices, twelve semitones, yep only one voice.

[chrisakaneelix]

Yep, if it's not the same physical key every time, but every 6th note you play (regardless of keys), it's definitely an individual voice. Hopefully just a calibration, but the voice chips can just go awry after a while (amplifier or filter staying open). Fortunately they're not too hard to track down, but not super cheap. If I remember correctly, those are vertical single sided chips, so not too hard to solder in...
Best of luck!!

[burymyteeth]

Thanks very much for the info! I have to put it back together because am attempting to fix the after touch at the same time, will post my findings in the next day or two, which will hopefully be that I scored a now fully functional jx-8p for $200