Roland G-303/ G-808 - cleaning pots

Started by yogamuse, April 28, 2015, 12:25:42 PM

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yogamuse

Hi all,
I got a GR-300 in my shop the other day for a set-up and it now plays great with the 24 pin - 13 pin converter doing a beautiful job - but it has scratchy pots on the normal p/u section. As you see, these pots are a part of a larger scheme. Can I get some cleaner/lube (de-oxit?) in those pots from the outside?  I'd rather not dig too deep into this...
Thanks for any advise.

admin

#1

yogamuse

#2
I imagine the whole assembly will come out if I remove the pot hardware. Concerned about breaking/ cracking  the tophat knobs. Gotta come off either way. Think Im going to try spraying deoxit from the outside first. Thanks.

yogamuse

#3
Thanks for sending this, but I didn't see anywhere it references cleaning the pots. Is there a page no. I should be looking at? It's great to have for the files anyway, so, thanks again!

In any case, I was able to get the De-Oxit into the pot from the outside without a problem. Quiet as a mouse now. So - in answer to my own and maybe someone else's question, yes, you CAN clean and lube the pots on a GR-300 without removing the harness. Just be careful removing the knobs, they're quite brittle.

Elantric

#4
Glad you got the pots cleaned


groovey1

Quote from: yogamuse on April 29, 2015, 10:54:15 AM
Thanks for sending this, but I didn't see anywhere it references cleaning the pots. Is there a page no. I should be looking at? It's great to have for the files anyway, so, thanks again!

In any case, I was able to get the De-Oxit into the pot from the outside without a problem. Quiet as a mouse now. So - in answer to my own and maybe someone else's question, yes, you CAN clean and lube the pots on a GR-300 without removing the harness. Just be careful removing the knobs, they're quite brittle.

Sorry to bring back an old thread, but I'm not having much luck get rid of the crackle in the volume pot of my GR-300. Did you get the De-Oxit in from the front of the guitar? Or in through the back somehow?
Thanks,

MrSparkle

Way late reply here, but I recently got a G303 and the (normal pickup) Tone knob was very scratchy. I didn't want to try prying the original knob off, I just de-oxit sprayed around the sides and it's working fine.

The small black VCF Resonance knob on the guitar is acting a little funny though. I'm unsure whether it's the pot, the cable or the unit, but there are some strange things happening when it's dialed back. Sometimes the synth entirely cuts out. One thing that definitely cuts all hex sound out is moving any of the GR-300's controls, only when the VCF Res. knob is down.

If the VCF Res. is full (which is my less favorite tone... a little to aggressive, especially with the funky auto-filter sounds), it seems to work fine, but dialing it back seems to create chaos on the GR-300 board. Eventually it settles in and works fine.

I tried spraying it and it took a little bit of scratchiness out, but it seems the issues I'm talking about are unrelated. Not sure if De-Oxit on the synth pots is a good idea anyhow.

chrish

I don't know if it's weird voltage from your power supply but the gr 300 gurus suggest changing the blue capacitors in the power supply because they were known to fail.

I think Wayne Joness has a some meter test that can be done up on his site to determine whether or not the capacitors have failed.

GuitarBuilder

Quote from: MrSparkle on September 08, 2017, 06:13:38 PM
Way late reply here, but I recently got a G303 and the (normal pickup) Tone knob was very scratchy. I didn't want to try prying the original knob off, I just de-oxit sprayed around the sides and it's working fine.

The small black VCF Resonance knob on the guitar is acting a little funny though. I'm unsure whether it's the pot, the cable or the unit, but there are some strange things happening when it's dialed back. Sometimes the synth entirely cuts out. One thing that definitely cuts all hex sound out is moving any of the GR-300's controls, only when the VCF Res. knob is down.

If the VCF Res. is full (which is my less favorite tone... a little to aggressive, especially with the funky auto-filter sounds), it seems to work fine, but dialing it back seems to create chaos on the GR-300 board. Eventually it settles in and works fine.

I tried spraying it and it took a little bit of scratchiness out, but it seems the issues I'm talking about are unrelated. Not sure if De-Oxit on the synth pots is a good idea anyhow.

Download the service manual and follow the setup/checkout instructions.
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973

chrish

#9
Quote from: MrSparkle on September 08, 2017, 06:13:38 PM
Way late reply here, but I recently got a G303 and the (normal pickup) Tone knob was very scratchy. I didn't want to try prying the original knob off, I just de-oxit sprayed around the sides and it's working fine.

The small black VCF Resonance knob on the guitar is acting a little funny though. I'm unsure whether it's the pot, the cable or the unit, but there are some strange things happening when it's dialed back. Sometimes the synth entirely cuts out. One thing that definitely cuts all hex sound out is moving any of the GR-300's controls, only when the VCF Res. knob is down.

If the VCF Res. is full (which is my less favorite tone... a little to aggressive, especially with the funky auto-filter sounds), it seems to work fine, but dialing it back seems to create chaos on the GR-300 board. Eventually it settles in and works fine.

I tried spraying it and it took a little bit of scratchiness out, but it seems the issues I'm talking about are unrelated. Not sure if De-Oxit on the synth pots is a good idea anyhow.
I saw a picture of the inside of a GR300  on reverb.com where it shows the unit being Model A. Right above that board Model number is a blue barrel capacitor where it looks like electrolyte from the capacitor is leaking onto the board traces. Could that possibly be shorting the traces?

If that is leaking electrolyte it would seem like that capacitor would need to be replaced and maybe others and the board cleaned with isopropyl alcohol. But then again I'm no expert.

https://reverb.com/item/6739216-roland-gr-300-guitar-synth-24-pin-cable-clean-shape-powers-up-and-works-well-small-vcf-issue

MrSparkle

Quote from: chrish on October 01, 2017, 09:47:23 AM
I saw a picture of the inside of a GR300  on reverb.com where it shows the unit being Model A. Right above that board Model number is a blue barrel capacitor where it looks like electrolyte from the capacitor is leaking onto the board traces. Could that possibly be shorting the traces?

If that is leaking electrolyte it would seem like that capacitor would need to be replaced and maybe others and the board cleaned with isopropyl alcohol. But then again I'm no expert.

https://reverb.com/item/6739216-roland-gr-300-guitar-synth-24-pin-cable-clean-shape-powers-up-and-works-well-small-vcf-issue

That's mine for sale there! I listed it on the high side to prevent a sale at the moment as I wanted to figure out what exactly is wrong with it before selling and may have somebody who can do the repair work... You have a sharp eye! Here's a closer pic and you may be right from the looks of it.

chrish

#11
That's not a bad marketing strategy because you're including a 24 pin cord and the cords seem to fetch a good amount of money.

The cord is easy to test with the continuity setting on a meter.

I've seen non-functional gr 300 on eBay go for $300.

It was interesting to see a photo of the model A board.

Here's a photo of my model C board. Notice that I've only replaced one of the capacitors in the power supply so far.





This quote from Dr.Joness site.

http://www.joness.com/gr300/GR-300.htm

"There are three versions of the Roland GR-300. These are distinguished by the letters "A", "B" or "C" appended to the part number printed on the top voice board. The only way to know which version you have is to remove the bottom panel, and look at the printing in the lower right-hand corner of the voice board. You will see either 052-539A, 52-539B, or 52-539C.
Of the three versions, "C" is the most common, and the most desirable. Electronically and functionally, these GR-300s are the same. However, version "C" is the version referred to in the well-documented Roland GR-300 service manual. Version "A" is notable for the fact that many components are found tack soldered onto the circuit board. Apparently when the circuit board was produced, some components were left off the circuit board, and so capacitors, transistors, etc. were soldered to existing components to complete the circuit. Also, there is a small network of resistors added to the power supply, not documented in the service manual, and not included in the more common version "B" and "C". The final curiosity are the two, 12 pin ribbon connectors. In all other Roland products, the two 12-pin connectors are positioned parallel, side-by-side. This configuration is in line with the way the ribbon connects to the 24-pin cable connectors. However, on the version "A" synth, the two 12-pin connectors are in series, which makes it more difficult to connect the ribbon to them."


chrish

Before I remove the knobs from a Roland G505  guitar that was made in 1982, are there any precautions I should take or sprays like silicone I should apply to the knob shaft interface.?

They appear to be really stuck on there and can't be removed with just hand pressure so I'm going to have to use some sort of pry bar pressure.


chrish

Thanks. it looks like that tool distributes the pressure evenly over the knob.
I hadn't thought of that.

Elantric

#15
it helps to place a thin old mouse pad under the knob lifter tool - protects the guitar finish  / pant 

See more Guitar repair tools here:
http://www.philadelphialuthiertools.com/
http://www.philadelphialuthiertools.com/misc-tools/?sort=featured&page=2