JP8000 Detune problem

[cheezykeyz]

Hi,

Recently my JP8000 started going out of tune, which is strange for a digital synth. I tracked it down to the pitch bend and could see a lot of jitter on its controller lane when recording the midi messages in cubase. Had the unit serviced and the pitch bend joystick replaced and still the same problem. I took it back and the service engineer reckons there's a leakage from a resistor on the main board causing the pitch bend to be be applied ever so slightly. I've taken the main board out and will check it out at work but I was just wondering if anyone else has had this problem and knows of it's cause? If not can you still buy a new main board assembly?

Many Thanks,
Martin.

[MarkShovel]

I was able to fix my ribbon controller with a calibration routine. I ordered a replacement ribbon, but with the calibration, I've got acceptable operation. Please check the bender calibration shown below:



1. Turn the Power on While holding down [OSC2 SYNC] [-12dB/-24dB] and [FILTER TYPE]
2. Test mode is now in operation and the memory test begins.

The Tests are as follows

1. Memory Test
2. [1] MIDI Test
3. [2] Switch and LED test
4. [3] Adjusting Bender and MOD
5. [4] Adjusting Ribbon sensor
6. [5] A/D test
7. [6] Hold pedal test
8. [7] LCD test
9. [8] Sound Test

Exiting a test

Press the number button to quit the current test and start another test.
For the SW&LED test press the number button while holding down The [WRITE] button.

Exiting the test mode

(When the test is SW&LED, exit it)
Press [SHIFT/EXIT], Then "Are you sure?' is displayed.
Press [WRITE] to exit the test mode, then factory data will be loaded.



4. Adjusting Bender & Mod
On the Display you will have "[3] Bend Mod ??? ???"
(where ??? is the Hex value of the bender and mod)
Push the bender lever left fully and gradually return it to the original position.
Press the [LOWER] button.
Push the bender lever rightward fully and then gradually return it to the original position.
Press the [UPPER] button.
Push the bender lever to the MOD position and then gradually return it to the original position.
Press the [KEY MODE] button
Then an '*' appears press the [UP] button then the '*' changes to a '' mark

Moving the bender you should get these readings, left -256 center 0 right 255
Moving the bender into the MOD position it should go up to 127 and then return to 0.
Now if the above things doesn?t happen, press the [3] button and readjust, if still not correct, take the keyboard to Roland service, as there could be a problem with either the bender unit itself, or some of the IC's could need to be replaced.

[cheezykeyz]

Thanks for the advice, at least I know where the test mode is now. After calibrating the pitch bend I would get a value of -256 when pushing the joystick left. A value of 60 for right and when I push it up I get 127 but the bend displays a varying value from 248 to 257. Looks like there is a problem with the main board, without the schematics I'm lost at what to do. Does anyone know which IC's are likely to cause the problem?

[Synthia]

I had some similar problems with my JP8000 last year.

I also did the calibration routine and now it seems to be ok.

It still self edits sometimes which is annoying.

http://www.jupiter-music.com/synthia.htm
http://www.myspace.com/tritonia
Music keeps me sane in an insane world!