GR-1 no sound or distorted sound for several minutes

Started by randulo, August 25, 2016, 04:23:42 PM

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randulo

My GR-1 is old and has been played less lately, but I have two questions.

For a while now, when I first turn it on, sometimes it comes on normally, but others, there's a variable time where there's no synth or guitar out or sometimes a very soft and distorted one. I've tapped it, I've taken it completely apart and bent the board, I 've  tried every trick I know to find the fault, but can't.
The problem seems to be in the final stages of amplification because the synth sound are working.

1. Is this an electrolytic capacitor gone/going bad somewhere?

2. Does anyone know a competent tech that might fix this in the Santa Barbara, Ventura or Los Angeles area?

I am leaving this with a friend, but I'll come back to it from time to time. Right now, the only way to be sure it works is to never turn it off :-)

Sorry, looks like I already mentioned this but in the wrong place. I said it in the FAQ for some reason. Maybe better in its own thread here?

Hopeful GR-55 convert from GR-1
Twitter @randulo
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Elantric

#1
Quote1. Is this an electrolytic capacitor gone/going bad somewhere?

Very likely - yes
http://www.rolandus.com/support/service_repair/service_centers



AngeloEvs

Just in case some one browses this thread with a similar problem.   My GR1 suddenly lost output,  everything appears to function but no output from any of the output jacks.     

In my case the fault was traced to the -7v rail missing on IC1 and IC2 which are the analogue output op  amps.

Further testing found C4 electrolytic capacitor short circuit.    The op amps should have +7v and -7v but note that both are fed via a 33 ohm resistor (R34 and R35) each having a 470uf 10v electrolytic capacitor.  These resistors isolate the op amp supply from the main +7v and -7v supply used for the GK pick up and other analogue parts of the system.  Best to replace both if necessary.

starlessffxi

@randulo

Wow thank you for supplying that info on the resistors. I would have had no idea, I only saw old leaky capcacitors. Sure enough after seeing your post, both of these resistors are open.

My problem is different than what is described here though.  On mine, only 2 strings seem to work somewhat normally, the others are basically not sounding or detecting. But I have a feeling this is all related to this known fault.

Cheers,
Keith

Mrelectric

Hi,
Just to add to the body of knowledge for the hive, I have an old GR1(1.02ROM even!).
I also had problems with low audio output , which would increase gradually to the maximum after some minutes. I replaced most of the PSU electrolytics. Certainly one showed signs of outgassing.
Having changed the output op amps for modern quality types, I then spent some time with the mute circuit,  which turned out to be the cause of the problem.
I eventually came to the conclusion that the local electrolytic caps were faulty (leaky) and I replaced C105 and C106 with new electrolytic 100uf and ceramic 1uf. Still get a loud click on power up but with the volume turned down it isn't as bad. On power off the noise is minimal, so I can live with this.
Took a bit of finding and I was considering replacing it with a more reliable design but it I s good enough now.
I'll be interested if other people have had similar root causes.
Best regards,
David

Waltheer

Raising this Thread from the dead, but I figured it made no sense opening a new one, as my issue is similar.

-My issue is that I can't get any synth sound output- on any output jacks,
Clean guitar is loud and clear, I can control other synths using the GR-1 midi out, but alas, no onboard synth sound.

-I tried a factory reset, but it just hangs forever on the "wait" screen I'm guessing this might be related to the issue.

Any thoughts before i start changing/ tracing everything?

gumtown

Change the internal lithium CR2032 button cell.
Let the system discharge for 30 minutes before installing the new one (do not power on during this).
All your saved settings and patches will be reset, but any unstable state will also be reset.
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

chrish

Quote from: gumtown on November 09, 2021, 10:16:00 AM
Change the internal lithium CR2032 button cell.
Let the system discharge for 30 minutes before installing the new one (do not power on during this).
All your saved settings and patches will be reset, but any unstable state will also be reset.
is letting it discharge just so you don't accidentally touch something with voltage?

I just changed the battery in a GR50 which restored the internal sounds, is the batt holder itself a potential voltage source or just the caps?

Waltheer

Well, saying the battery trick didnt work might be an understatement...

https://www.youtube.com/shorts/RzkmD-W5KS8

Can't get into the system menu to try and re-upload the original sysex file...

any ideas?

gumtown

Quote from: chrish on November 09, 2021, 11:27:55 AM
is letting it discharge just so you don't accidentally touch something with voltage?

I just changed the battery in a GR50 which restored the internal sounds, is the batt holder itself a potential voltage source or just the caps?
Letting the CMOS memory discharge fully is the reason why, Roland gear is partial to corrupted memory when a lithium cell runs too low,
replacing the lithium cell quickly will retain the corrupted CMOS memory data.

Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

gumtown

Quote from: Waltheer on November 09, 2021, 12:46:51 PM
Well, saying the battery trick didnt work might be an understatement...

https://www.youtube.com/shorts/RzkmD-W5KS8

Can't get into the system menu to try and re-upload the original sysex file...

any ideas?

Power supply issues there,
if the GR-1 is continuously rebooting, a typical sign that electrolytic capacitors have dried up,
and not enough storage capacity left for the startup in rush of current.

the typical lifespan of modern electrolytic caps is designed for 10 years,
so you may get up to 20 years on a good one. (manufacturer specs and quality vary).

 
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

Waltheer

By power supply you mean the onboard Caps? Or the ones in the power supply?


chrish

#13
That's common for that synth. Read lots of reports of smoking GR1's when they haven't been used for a while or from people buying used ones.

Quote from: gumtown on November 09, 2021, 01:28:26 PM
Letting the CMOS memory discharge fully is the reason why, Roland gear is partial to corrupted memory when a lithium cell runs too low,
replacing the lithium cell quickly will retain the corrupted CMOS memory data.


that's a new bit of learning, thanks.

Cool thing is after I changed the battery the patches were the original sample patches which I like. Numbered Sample Patch 1, Sample Patch 2 etc.


Kind of like a Hal2000 computer before its corrupted with faulty instructions.  :)

gumtown

Quote from: chrish on November 09, 2021, 03:36:18 PM

Kind of like a Hal2000 computer before its corrupted with faulty instructions.  :)

Exactly !!
Sorry Dave I can't let you do that.  :o
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/