Need help troubleshooting RMC system. RMC hasn't replied in a couple of days.

Started by myka-x, April 04, 2013, 01:23:01 PM

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myka-x

Hi All,

I am working on a simple installation, or so I thought, of an RMC PolyDrive I internal preamp. I am having some trouble and RMC seems very busy, I haven't heard back from them in a couple days. They do answer within hours when I order something so their support staff must be limited.

The guitar is a custom I am building for a client and the setup is extremely simple:

1) Magnetics completely separate
2) Piezo on separate output, not passed through the 13-pin
3) Polyphonic preamp setup to use only the Program Up/Down switch. No hex volume, and no gtr-mix-synth switch.

My problem is that I am not getting any hex output at all. I would assume that if I didn't need a knob or switch I would leave it disconnected and by default it would work. This does not seem to be the case.

Using this diagram: http://www.midiguitar.net/group/RMC/RMC%20PolyDrive%20I%20connections/PD1ins3.pdf

1) Pins 1,2, and 3 wired to the Program Up/Down momentary
2) Pins 4 and 5 are hard wired for full hex volume, pin 6 is ground
3) Pins 7,8, and 9 are not connected. Pin 8 is a ground and the signals are grounded to select them. Both should be the default.
4) Pins 10 is the summed piezo signal which is sent to a separate output along with one of the grounds. Pins 11, 12, and 13 are not connected.
5) Pin 15 is the battery switch and is on the piezo output ring. Pins 14 and 16 are not used.

Is there anything obvious that I seem to have missed? Do I have to run the summed piezo (pin 10) through the preamp (pin 11) and use the outputs wires provided (pins 14 and 16)?

The piezos work so the saddles are connected. But there is no hex signal at all. I have looked at all of my wiring for shorts and cannot find anything. It is a very simple wiring so I am not sure what else I can try. The last installation of RMC went totally smooth. This one has me stumped.

Thanks for any and all help!~

~David


Elantric

Quote3) Polyphonic preamp setup to use only the Program Up/Down switch. No hex volume,
Sounds to me like your omission of the GK Vol Pot is the problem.

Remember the GK Vol Pot feeding Pin#8 is a Control Voltage.

(0 Volts on Roland Gk13 cable Pin 8 = No Sound Output on GR-55 / VG-99)

(+5 Volts on Roland Gk13 cable Pin 8 = Max Sound Output on GR-55 / VG-99)

With no GK Synth Volume Pot - you essentially are forcing the target 13 pin device (VG-99 / GR-55)  to be  Muted.

QuoteUsing this diagram: http://www.midiguitar.net/group/RMC/RMC%20PolyDrive%20I%20connections/PD1ins3.pdf
Hopefully you have more pages of PolyDrive 1 install docs than this, as you only have 50% of the required info for a full  RMC Polydrive 1 installation


See here - or see attached
http://www.midiguitar.net/group/RMC/RMC%20PolyDrive%20I%20connections/PD1ins1.pdf

You need a small 250K Audio taper pot, installed and wired exactly as described in the RMC Polydrive I installation docs, and just leave it in the internal control cavity.

Or

replace it with a 250K or 220K resistor





Referring to the RMC Polydrive install page 1 above - do the following to "fool" the circuit into thinking you have a Synth Volume Pot always on Max full volume.


STEP#1) Referring to the RMC Polydrive install page 1 above, Look on the left for the RMC connections descriptions

   RIBBON CABLE     Function
   ======================
   4 - YELLOW      - Synth Volume pin 3
   5 - GREEN        - Synth Volume pin 2
   6 - BLUE          - Synth Volume pin 1

STEP#2) Solder a shorting jumper wire to connect these two connections together
   RIBBON CABLE  Pin# 4 - YELLOW
   RIBBON CABLE  Pin#5 - GREEN


STEP#3) Obtain a 220K resistor. We will use this to replace the missing Synth Volume POT.
Connect one end of the 220K resistor to the electrically shorted Ribbon Cable's Pin's 4 & 5 connections described in Step #2

STEP#4) Connect the remaining end of the 220K resistor to Ribbon Cable pin#6 - BLUE. This same connection must also be tied to Ground.

This will complete the Synth Volume circuit and you should be able to measure close to +5Volts on the Roland GK DIN13 Pin #8, to "fool" the circuit into thinking you have a Synth Volume Pot always on Max full volume.



See this link for details on  full  RMC Polydrive 1 installation
https://www.vguitarforums.com/smf/index.php?topic=571.0



myka-x

Hi Elantric,

Thank you for the reply.

I thought that I took care of the control voltage by connecting pins 4 and 5. When it is on full volume pins 4 and 5 read as a connection on my multimeter and so I assumed I could simply hard wire it instead. I just tested it by wiring in the hex volume pot and it seems to work perfectly.

I will take your advice and wire it in with the resistor inside the control cavity.

Thank you. This saved me a major headache!~

~David

Elantric

QuoteWhen it is on full volume pins 4 and 5 read as a connection on my multimeter and so I assumed I could simply hard wire it instead.

A common mistake.


Oh and Welcome to the Forum!

Ive heard many good things about Myka Guitars.
Really dig your work for Vance Galoway last year.

https://www.vguitarforums.com/smf/index.php?topic=6097.msg41841#msg41841



And this thread may help countless others, so I REALLY appreciate you posting your PolyDrive 1 install problems here

myka-x

Thanks, that was a fun project with Vance. He lives right down the street from my shop. We are always talking about new ideas in the hex/ergonomic guitar universe. I am currently working on a personal instrument with a hex system in it. The trem I am using is a Skyway and I am thinking that I will try and install the mini magnetic pickups in a Roland GK pickup onto the ends of each saddle. That way they are always in the same position relative to the string. I'll post something here when I get started with that.

About the resistor value, I tried 4.7k but it didn't work. RMC specs a 250k pot so I used a 220k resistor and it did work. Also, RMC responded this afternoon and they recommended the same 220k value. They also recommend using a 1-2k resistor in series with the piezo signal to protect from voltage spikes when running it directly from pin 10 (when sent to an isolated output).

QuoteREMOVE PIN#6 FROM GROUND
I double checked and Pin 6 on the ribbon cable is a ground connection on the RMC board (along with 2, 8, 13, and 14).

Thanks again for the help. The project is now coming together.

~David

Elantric

Thanks for the update!

I mistook the 5K "Blend" pot for the 250K Synth Vol Pot! Updated the instructions above accordingly

Glad Richard McClish set you straight.

QuoteThe trem I am using is a Skyway
http://www.skywaymusic.com/

Re:Skyway Tremolo bridges I contacted that guy a few times - he tells me he's always too busy, and has zero product to sell me.
His site is now over 5 years old with zero updates, and zero product for sale.
Tell him bulk of his potential Skyway Bridge sales are now being fulfilled by SuperVee Bladerunners


Glad you were able to obtain the "unobtainium"