Problem with volume on GR-55 with GK3 pickup

Started by mmccain, April 10, 2023, 01:20:45 PM

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mmccain

Most of my GR-55 patches are configured to use the pot on the GK-3 pickup as volume.  It didn't used to do this, but at some point, when the the GK-Volume pot is past approximately 85-90% CW (almost full on), the patch goes mute -- to zero volume.  If I back it down to less than 85-90%, the volume comes back up again.  It is this way with all patches that use the pot for volume.  I'm not sure if accidentally made some global change that caused the pot to go out of calibration, or what happened.  Any ideas on how to correct this?  Otherwise, the pot works fine -- not like a dirty spot.  I looked for some sort of calibration procedure, but I don't find anything. Thanks in advance for your help.

Elantric

Upload one of your patches for others to test

philjynx

Quote from: mmccain on April 10, 2023, 01:20:45 PM...  Otherwise, the pot works fine -- not like a dirty spot...
Do you mean it works fine in patches where it is not being used for volume but used for some other function?

gumtown

It could be a faulty pot due to the GK-3 knob being compressed if a guitar is stored in a fitted case where the padded liner presses on it when the lid is closed.

Another area to look at is the GK cable or its connection pins.

There are no calibration settings for this, the GK pickup circuit controlled by the pot sends 0~5 volts to the floor processor on one core of the GK cable.
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

plexified

#4
If we were to recreate this situation, we would have to use assigns to do so. Globally you cannot program the unit to do what you describe. Upload a patch as Elantric has suggested and so far, as gumtown has described the cable/pot seems to be the issue. A physical issue. Here you can try to clean the cable pins , pot for a 'physical' repair.

mmccain

Problem solved...well, diagnosed.  It did turn out to be a flaky volume pot.  When I brought it home from the theater where it has lived for several years, I was able to actually troubleshoot.  A bit of pressure in one direction would cause the sound to come back.  I found no cracked solder joints but re-soldered anyway.  Got a bit of DeOxit to drip down in the pot and that helped a little.  I'm in the process of ordering a replacement pot from Roland.  I Googled the  alpha b50k 1L2 part number on the component, wasn't sure if it was linear or non-linear, so I just went straight to Roland.  Thanks!

Elantric

#6
Roland US allowed you to order the part?



That's a change, as in 2010 they canceled selling parts to USA  consumers
Describe the process you used to order Roland Parts

mmccain

No order has been confirmed yet, but I went to the Roland website, logged into my account, selected Service, then Service and Repair, then Parts Order Request.  Filled out the online form, and it said they would be contacting me.  They have not contacted me yet.  So...I dunno.

Elantric

#8
If you are lucky, a local official Independent Roland/Boss Warranty repair facility can sell you the part

It's a 50k Linear pot 

GK-3 Service Notes
https://www.vguitarforums.com/smf/index.php?action=dlattach;attach=6628

ALPHA # RV09A-40-15F-B50K
Roland # F3229149

https://www.merktron.com/sqlcommerce/disenos/plantilla1/seccion/producto/DetalleProducto.jsp?idIdioma=&idTienda=410&codProducto=F3229149&cPath=273


gumbo

...if nothing happens, we'll help you watch the paint dry... ::)
Read slower!!!   ....I'm typing as fast as I can...

mmccain

Taking your "watch the paint dry" comment to heart, I decided not to wait on Roland. Mouser.com (one of my usual component sources) didn't have it -- or at least I couldn't find it.  But...I did find a Uxcell Carbon Film Potentiometer, 50K Ohm Variable Resistor Single Turn Rotary Half Shaft D on Amazon (item number a19032800ux0942).  I had to cut the (plastic) shaft length down to around 6mm and extend the flat side down all the way (Dremel tool), but it worked just fine. The footprint worked, but it doesn't have the four green posts on the bottom like the original.  But at least it fits and works fine.  It was a pack of ten for $9.99, so I'm all set with plenty of extras if this one doesn't hold up.  Fortunately I don't turn the pot that much. It was probably damaged as Gumtown suggested earlier in one of the numerous times the guitar got squeezed into an overhead bin in its gig bag.  And...I just got a reply from Roland saying they don't sell direct to consumers and I'd have to contact an authorized service center, bla bla bla...