JP8000 ribbon controller problem

Did you try cleaning it? The ribbon controller on mine was acting super wonky until I cleaned off the accumulated years of finger oils grease and dirt. They are super easy to switch out, too, so if that doesn't take care of it just order a new one (you can find them online for cheap).

BlackRyder wrote:

Did you try cleaning it? The ribbon controller on mine was acting super wonky until I cleaned off the accumulated years of finger oils grease and dirt. They are super easy to switch out, too, so if that doesn't take care of it just order a new one (you can find them online for cheap).

Hi, what did you clean it with? Also where have you seen them being sold because Roland are no longer supplying this part which is annoying!!!

The only place I've seen them for sale is here but at a rip-off price because this part was sold at only £15 direct from Roland UK.

http://syntaur.com/Items.asp?Item=3308

Fast Zee wrote:

Hello

Following battery replacement in my JP8000, I have re-calibrated the pitch bend and ribbon controller as this is generally required. Pitch bend works OK but the ribbon controller is giving me problems. I have reset factory settings and the issue remains.
From the test mode, when calibrating the ribbon controller, you would calibrate the left end, followed by the right, then the middle. However, it should be "off" when you start the calibration but the display is showing a value even when I'm not pressing the ribbon. Anyone experienced this before; any ideas whether this is a hardware or something I need to do? Any thoughts on how to resolve please?
The problem is that when playing, the ribbon is permanently set to its "left" value and as on many patches the ribbon applies a filter, loads of my sounds are massively filtered, lacking presence, volume and brightness.

Many thanks
Nick Z

Hi Nick,

Same issue here, there is another thread on this strange behavior.
Can you activate "Hold" and "Relative" and *does this make any difference* ?
So far I couldn't track down the root cause but what I can say, seems it is not the sensor itself but something with the electronics behind.

Kind regards,
Pete66

Gents,

Just to let you know that I fixed this issue.
It was actually the ribbon sensor which I replaced with a comparable but not compatible part (impossible to get these days).
Everything including Hold and Relative works well again. Total cost was about 8 Euros. :-)

Best,
Piet66

Wait ... is it the part you replaced that's impossible to find today? Or the original?

Please post here what was the replacement you used as this might be useful to us in the future.

Maybe I will already buy one or to just in case.

Thanks!!

Hi,

I couldn't get hold of the original part therefore used a different part.
The sticker on the wrapping says:
Linear SoftPot (Ribbon Sensor)
P178
Http://adafru.it/178
This is the dealer, manufacturer is "Spectra Symbol" as printed on the ribbon sensor.
Maybe there are also other sources however I didn't ceck.

This sensor was the best/closest fit I could find in terms of physical dimensions and electrical values.

Note: For implementation
- I turned the ribbon by 180 degree, ie. differently to the original part contacts show towards the inside of the synth.
- I soldered three wires to the ribbon before installation.
- at the other end wires are soldered to the PCB where the ribbon connector sits.
- one pin of the ribbon sensor has a marking " >". This goes to pin 7-8 of the connector, the middle pin goes to 1-2 and the remaining pin goes to 4-5.
- carefully center the touch zone of the ribbon sensor in the middle of the black touch stripe before glueing the sensor (the sensor comes with a self-adhesive 3M strip).
- There are two fixation points (small plastic knobs in the synth case) which fit to two holes in the original sensor. I removed the knob showing towards the inside of the synth with a sharp knife . If you don’t do this, the replacement ribbon may be damaged (perforated by the tiny plastic knob) when screwing down the metal plate. No need to remove the other knob.

After sensor replacement you need to perform the known test sequence [#4] for ribbon calibration.

Good luck everyone & Hope this is useful for you.

Best,
Piet66

Thanks Piet ... this will definitely help a lot of people.

Thank you so so much.

Hi mockba_the_borg,

My pleasure, any questions please let me know.

Kind regards,
Piet66

Registered just to thank Piet66 for the help.

My JP8000 works perfectly now!
[attachment: 20210922_201546.jpg]

Hello pattern9,

Great, I‘m happy it works for you!

Cheers,
Piet66

Hi

Having a similar problem with my JP-8000's ribbon I came across this thread and I can say big thank you to Piet66 for all the testing and information provided here.

However, I was not satisfied with the solution of buying new ribbon because I had an impression that the old ribbon was actually working which was also measured by Piet66. I have also measured my ribbon and it had similarly around 20Kohm.

Looking at the schematic the only 2 things that came to my mind was 1. The ribbon had developed some kind of small leakage current. 2. The ribbon's resistance has changed over time. By further measurements I concluded that leakage current was not the case so the second option that the ribbon resistance has changed over time is the most probable one.

Searching alternative ribbons on the net confirmed that almost all ribbons have around 10Kohms of resistance so I guess that the original was also 10Kohm.
By further analyzing the schematic the way of reading the ribbon value by using two ADC values instead of one was not good design by Roland at all resulting in a strange software method that they used here. They measure the resistance of all the ribbon (I don't know why??) and they measure the voltage (the finger position) also. This implementation has it's benefits like testing if the ribbon is OK however small change of it's characteristics result in this weird problem.

By testing the humbers that I get when changing the overal ribbon resistance I concluded that the software in the JP-8000 expects a ribbon resistance between 7 and 15Kohm to display "Ribbon OFF" in the Ribbon test mode. So it's a bit off but I found an elegant solution: In the schematic there is a ribbon voltage divider resistor marked R105 that id 3.3Kohm. This resistor shluld be increased in order for this aging ribbon to display "Ribbon OFF" again. I simply removed the resistor and put a 10Kohm variable resistor (trimmer) to its place on the solder side and set the trimmer to display "Ribbon OFF" and problem solved.

You can now calibrate the ribbon again and it all working OK with the original ribbon. I hope this will help someone.