GK2A GTR/MIX/SYNTH... Again!

Started by pasha811, January 04, 2024, 07:44:28 AM

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pasha811

I have read a lot regarding the differences between GK2A and GK3.
My humble understanding is that with GK3 the Switch (GTR/MIX/SYNTH) can be used in the Patch design as in GTR mode it excludes COSM Guitar.
However, recently I repaired a broken GK2A by swapping the Pre-Amp board with a new one from Roland. Then, with my surprise I noticed that when switching it to GTR (Guitar) the Volume of the COSM Guitar goes to 0 while in MIX or SYNTH position goes to 100. That is consistent with what my GK3 equipped guitar does... so I am afraid I have not got the difference or I have a Pre-Amp board in my new GK2A that behaves as a GK3.
All of this happens with VG99.

Thanks for helping!

 
Listen to my music at :  http://alonetone.com/pasha/

gumbo

I know that this is fairly basic, but what pickup setting is on your VG-99....what is it expecting as the inputting pickup?
Read slower!!!   ....I'm typing as fast as I can...

pasha811

Quote from: gumbo on January 05, 2024, 12:47:06 AMI know that this is fairly basic, but what pickup setting is on your VG-99....what is it expecting as the inputting pickup?

Hi Peter!
Thanks for reply. Happy Down Under 2024  :)
VG99 GK setting is set on GK2A and it cannot be mistaken because it has a particular sensibility setting (material for another post  :P )

Ciao
Paolo
 
Listen to my music at :  http://alonetone.com/pasha/

gumbo

Happy 2024 back to you to !

What would be an interesting thing to do (at least I would find it interesting !) is to see what (if any) signal(s) were coming down Pin 9...     If the board that Roland sold you as a duplicate GK2A is sending ANYTHING down that Pin, then the circuitry of the PCB is NOT a duplicate of the original GK2A..

...Problem is, I have enough bits-and-pieces here to patch together enough things to run a test like that, but YOU are a few thousand Kms away from me....and likely-as-not might have problem with setting up a probe circuit..

I will think about what you might need to achieve that and get back...my first thought is to dismantle the 13-pin jackplug on one end of the 13-pin cable, so you can get the probes of a multimeter onto the various Pins while the thing is plugged into both the GK2A and the VG-99.

Someone smarter than me, may come up with a better plan... :o


Cheers,
Peter
Read slower!!!   ....I'm typing as fast as I can...

pasha811

Quote from: gumbo on January 05, 2024, 03:37:57 AMHappy 2024 back to you to !

What would be an interesting thing to do (at least I would find it interesting !) is to see what (if any) signal(s) were coming down Pin 9...     If the board that Roland sold you as a duplicate GK2A is sending ANYTHING down that Pin, then the circuitry of the PCB is NOT a duplicate of the original GK2A..

...Problem is, I have enough bits-and-pieces here to patch together enough things to run a test like that, but YOU are a few thousand Kms away from me....and likely-as-not might have problem with setting up a probe circuit..

I will think about what you might need to achieve that and get back...my first thought is to dismantle the 13-pin jackplug on one end of the 13-pin cable, so you can get the probes of a multimeter onto the various Pins while the thing is plugged into both the GK2A and the VG-99.

Someone smarter than me, may come up with a better plan... :o


Cheers,
Peter

Thanks Peter! So it's becoming intriguing right?
Adventurous! Considering my manual abilities  :P
First of all where is pin 9 (in the 13 Pin Connector) ?
I have cables I used for Arduino stuff and breadboard so I have female-male and male-male so I'd use the female-male to 'extract' pin 9 from my GK cable without dismantling it. Then I have a voltmeter.
However I see you need a Dynamic reading while all is connected, GK2A to VG99, otherwise the GK2A cannot get current from VG99... I still have the old PCB which, a part from the Normal Pickup female socket, is functioning (but not housed in the GK2A case).
To me it was curiosity, because my understanding was that GK2A should not behave like I observe...
Let's see if you or someone comes up with a less invasive solution (invasive as used in Medicine Diagnostic) even if I doubt that.  8)
Listen to my music at :  http://alonetone.com/pasha/

Elantric

#5
Quote from: pasha811 on January 04, 2024, 07:44:28 AMI have read a lot regarding the differences between GK2A and GK3.
My humble understanding is that with GK3 the Switch (GTR/MIX/SYNTH) can be used in the Patch design as in GTR mode it excludes COSM Guitar.
However, recently I repaired a broken GK2A by swapping the Pre-Amp board with a new one from Roland. Then, with my surprise I noticed that when switching it to GTR (Guitar) the Volume of the COSM Guitar goes to 0 while in MIX or SYNTH position goes to 100. That is consistent with what my GK3 equipped guitar does... so I am afraid I have not got the difference or I have a Pre-Amp board in my new GK2A that behaves as a GK3.
All of this happens with VG99.

Thanks for helping!

 

Review the GK-2A schematic and SW3 ON-OFF-ON Switch


The GK-2A SW3 "Guitar/Mix/Synth" 3 way switch operates by grounding (muting) the un-wanted signal - so what you experience is correct operation



SW3 in Synth ( COSM GUITAR) Position, the Normal Guitar Input signal is shunted to Ground= Muted Normal Guitar

SW3 in the Guitar Position, the GK VOL signal (VR1 Potentiometer that controls the Synth, or COSM GUITAR) is Shunted to  Ground, delivering Zero Volts on the Pin 8 GK-VOL control voltage output= Muted GK Synth, and 13 pin Guitar to MIDI Processors when GK-VOL pin8 signal is 0 Volts,  also transmit MIDI CC#7, or CC#11 value 0 , to mute any MIDI connected external Synth

SW3 in the Mix Position, neither Normal Guitar signal or GK-VOL ( for Synth) are shunted to Ground, and both can function

Managing GK13 Pin#8 "GK-VOL" 0-5VDC Control Voltage is mandatory for any GK13 Accessory, " Switch box or Internal GK 13 pin  pickup Installation. The Roland US-20 A/B/Y selector switch box is basically just rerouting or grounding the Pin#8 Control Voltage

If you omit GK-VOL on your custom guitar, or you simply do not connect it to to GK Internal Kit board, then Pin #8 will be stuck at 0 volts, and your GK Processor will not function.

On GK-2A, Pin 9 output is not connected, and its main purpose on the newer GK-3 is to identify (using control voltage to the connected GK Processor) if a Guitar ( GK-3), or Bass (GK-3B) is connected.


pasha811

#6
Thanks a lot Steve!

So my worries were unjustified. Good to know! Carry on Playing :-)

Listen to my music at :  http://alonetone.com/pasha/

gumbo

Ha!  Had completely (also!) forgotten about the differing voltages between the GK3 and the GK3B...thanks for the reminder, Steve...   ;)

Cheers,
Peter
Read slower!!!   ....I'm typing as fast as I can...