HELP!!! Roland GR-20 VERY Strange Behaviour - No minimum value allowed

Started by 6dB, February 05, 2016, 09:23:21 AM

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6dB

Hi folks! I just got a 2nd hand GR-20 and has a problem. It is constantly going between the patch selected and the next one, ie. if patch 81 is selected it cycles between 81 and 82, back and forth, thus you cannot play because the patch is being constantly switched. If I go to patch edit mode I can play, use both hold and glide footswitches, I can freely edit freq and reso values, but I can´t get minimum value on Transpose and Play Feel, as if there was a stuck +1 value all the time. I believe that this definetely happens at an electronic level, not mechanically, since switches, pots and rotary work perfect with other parameter, anyway I moved them and then fully dissasembled the unit and sprayed with contact cleaner just in case. Visual inspection on the board shows ok, caps are ok, etc. if I go into System Edit Mode I can´t get minimum value for any of the parameters, so I´m stuck to GA, Switch Mode 2 (can´t use hold or glide pedals but in patch edit mode), and Midi channel 2 thru 16. Same applies for glide type, hold type and expression pedal, no minimum value allowed so several features are unusable. tuner does not respond as well. I did a factory reset but since it goes back to switch mode 1, it starts the patch looping again between the patch selected and the next up. I tried it with a GK2A and also with a Godin Multiac ACS. I also have a GR30 and both guitars work perfect with it. I could not get any schematics for the GR20. It would be great if someone has it and post a link for it. Also I wanted to know if someone had similar problems and if is posible to solve it or the only way will be to get a replacement board, which besides expensive, will be nearly impossible on my location. It sucks not to be able to use the full features of the unit. I don´t know if there is any special Hard reset (besides the one with the write button) or test mode combination to run a self test (GR30 has it) that may get me closer to a fix. I hope someone can help me with this!!!! Thanks!!!

Elantric

On GR-20  - back up any user patches and perform a System Reset

and try a different Gk 13 pin Cable

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Roland GR-20 Initialization (Factory Reset)
Article #1709548 Added on Mar 20, 2012 at 3:11 PM
Use the following procedure to clear the GR-20's internal memory and reload its factory settings.

Caution: All User information is lost during a Factory Reset. Be sure to first back up anything you wish to keep before proceeding.

1. Power on while holding WRITE——"ALL" flashes in the display.

2. Release WRITE, and then press WRITE again.

6dB

Tried that already, I also have a GR30 with its corresponding 13 pin cable and it acts the same. I have a brand new spare cable, I will try with that but I suspect it will be the same also. I did the reset by holding WRITE and powering on as well. I thought about maybe trying to use sysex to send those unaccesible minimum values. Or try to run the smf files and upgrading the unit to v2, what do you think?

Elantric

QuoteI also have a GR30 with its corresponding 13 pin cable and it acts the same. I have a brand new spare cable
QuoteIt is constantly going between the patch selected and the next one, ie. if patch 81 is selected it cycles between 81 and 82, back and forth,
If by "Acts the same"  = you mean the GR-30 also  jumps up and down between 2 adjacent patches , Then you have a wiring problem elswhere  - possibly with your 13 pin guitar. 

6dB

No, I mean that the GR20 acts the same with all the different 13 pin cables I tried, even with the brand new one. The GR30 works perfectly as well as the GK2A and the Godin guitar

Elantric

Today , any 2005 era GR-20 will be over 10 years old - and the symptoms you experience appear to me to be related to age.

I would have a Roland Service center check the internal GR-20 power supply rails for excess noise  / ripple current - possibly due to the common problem of dried up bulk electrolytic caps on internal power supply PCB board

6dB

I understand what you say about the electrolytics drying up (I do musical gear repair), I checked them and at least visually the are fine. No ooze, residues, swolling, nothing. I´ll try to get my hands on a ESR meter to check the caps, since sometimes they do not show any exterior faults but go dead anyway. My GR30 is 10 years older than the GR20 and works flawessly, I guess the build quality and components used is getting cheaper and worse everyday, even on Roland products

Elantric

QuoteI´ll try to get my hands on a ESR meter to check the caps, since sometimes they do not show any exterior faults but go dead anyway.

Typically i just use my Tek 2440 analog oscope and visually inspect for AC ripple current on all internal DC power supply rails that reside within the GR-20 ( +7VDC , -7VDC, +5VDC, +3.3VDC)