GK-2A EXTERNAL-TO-INTERNAL CONVERSION NOTES

 

 

Roland GK-2A circuitboard

06/08/03- These are some preliminary notes and observations about converting Roland's externally mounting GK-2A divided pickup controller to an internal, inside-the-guitar mounting. I eventually decided not to do this conversion and installed a Graphtech Ghost piezo/Hexpander system instead. The job is very similar though; Both involve some major modifications to your guitar. Before undertaking something like it, it's a good idea to know what's involved and what your options are. That's why I explored this stuff.

WHY CONVERT AN EXTERNAL UNIT? Roland sells the pickup in kit form, which would be the preferred route since it's easier-- the parts are supplied with connectors and the kits (usually) contain all the switches you need. However, it's not really any cheaper in kit form and it's more likely that the aspiring synthesizer guitarist will acquire an external GK-2a pickup first, and then realize that he would prefer to have it mounted internally.

I'd thought about buying the upgrade kit and trying to sell the external unit, but for me, it would be difficult to accept the hassle of selling and the lost money-- it wouldn't be that much, but it's the principle of the thing. Converting and installing an external one isn't that much more work-- there's some extra disassembly, soldering and parts scrounging, but the hardest part-- the drastic guitar hacking-- is required in both cases, and for any Do-It-Yerself Roland-ready project. With the external GK-2A, you don't get the internal installation schematics or diagrams, but that's not a big deal since you can take good notes before you begin gutting.

D-I-Y VS. ROLAND-READY VS. TOP-O-DA-LINE Hacking up your guitar isn't for everyone, and fortunately there are alternatives. Roland-Ready Stratocasters are reputed to be decent choices. These are currently only available as "Made In Mexico" Stratocasters. Ego-wise, that's a tough one for some folks to swallow, and it's understandable considering the way our guitars become extensions of our personalities. Even though I may be a cheapskate, I sure don't want my beloved synth axe to declare it! That's just human nature-- we value status and bond with our guitars. We often view one as a "favorite". I'd rather have a Les Paul that said "Gibson" instead of "Epiphone", even if I couldn't tell the sonic difference. But there are actual quality differences, mainly in the choice of wood and some components. Many folks buy the Roland-Ready Strats and upgrade them with higher quality furnishings. If mucking with soldering and guitar drilling isn't your thing, and if you don't mind unleashing a bunch of extra parts, then that's a reasonable route to take.

It's still a tough choice. A discounted Roland-Ready Strat isn't that expensive and you get a lot more for your money than buying an internal GK-2a kit at full retail price. Of course, by the time the uber-Strat upgrades are in your Roland-Ready Strat, you've spent a lot of money... maybe nearly enough to have bought a better tracking Brian Moore or Godin in the first place? The least efficient scenario would be to have started with an external GK-2a, bought a Roland-Ready Strat, upgraded it, and then finally bought a Godin. That's probably happened a few times.

Of course, you could always just mount the pickup and external wart as Roland intended...

WHY BOTHER? That's a good question. The external "wart" does its job and doesn't permanently disfigure the guitar's wood. One could say that it's ugly, but that's a matter of taste. The extra bulk makes the guitar's fit into Fender's fitted hard shell case a little troubling at first glance. However, it's not a serious problem because, under the fake fur, the interior of that case is lined with a compressible styrofoam-ish lining.

The main practical reason that I see for doing it is to avoid the wear on the cord which connects the pickup to the wart's circuitry. It happens to run where your forearm rests. While I don't know of anyone complaining about this causing problems, opening the circuit case shows that there isn't much in the way of strain relief on the cord. It's held in place strictly by the pressure of the two plastic halves being screwed together. It could be a source of trouble. If you don't do the internal conversion, turning the wart over a few times before installing it on the body will make the cord coil into a cursive "S" shape, which takes up some of the slack and gets more of it out of the way of your forearm.

Another practical reason for the conversion is to wire your guitar's regular pickups directly to the wart's electronics. A soldered connection is always going to be more reliable than a jack/plug connection.

Mainly though, I think it has to do with the mindset of someone who likes the gadget side of guitars: We like guitars with lots of sound-wanking capability, and it's cooler when it's built in.

SIZING UP THE JOB A pesky detail-- we've gotta know how it's done to decide whether we're gonna be able to do it. Can we get the parts? Transferring circuit guts from one place to another isn't rocket science. Basically, you just replace circuitboard mounted switches, controls and jacks with mountable tethered ones. For the most part, it just requires decent soldering & desoldering skills. Generally speaking, before you desolder anything, it's a reaaaaaally good idea to make notes and diagrams of where stuff was connected. Label wires with sticky tags if necessary. Mark the board with a fine-tipped Pigma Micron pen if it'll help you.

This page was started after viewing a Japanese website which shows how it's done. Well, sort of... Did I mention that it's a Japanese website? Unless you can read Japanese, you'll probably rely on www.babelfish.com for the translation and maybe even figure out that "debye dead" means "divided" as in, "divided pickup". It's a difficult read, even if you try to think poetically and interpret in context (what could "leprosy" have to do with guitars?). But the site is a great source for giving you clues and has great photos and tables showing the circuit board pinouts.

Deciding on replacement switches may require a little bit of poking around to find out what they're doing. The "S1/Up" and "S2/Down" selector switches are momentary contact switches. The main question is whether the switches are normally open or normally closed-- from the Japanese text, they appear to be normally open, which would be what you'd expect for a latching-type circuit. However, to be sure, test the switch with an ohmmeter. You can probably test this without removing the switches (I forgot to). If they're normally open, you don't even need to remove them from the circuit board, just jumper the switch with an ohmmeter and press the switch to see what it does on the meter. My guess is that the two switches can be combined into a single 3-position, normally centered switch. I haven't done an extensive search on where one would find such a switch cheaply.

The 3-position mode selector switch looks a little bit more tricky, but from reading the translated text, I got the impression that the author found the switch "simple unexpectedly". Unfortunately, it's difficult to see what's going on with the two-sided circuit board since the switch covers the traces. However, I poked around with an ohmmeter and craned to see where the traces went. It appears that the 10-pole switch actually uses only 3 connections. Half of the switch appears to be unused, 2 of the contacts (internally connected to an adjacent contact) are snipped and don't connect to anything. For the mixed center position, no connections are made at all. In the guitar and synthesizer positions, the two traces switch to the center contact, which is grounded. If so, this could be done with a very basic and common 3-position switch. Beats me why they used such a specialty switch unless it was the only style which accommodated the fancy switch paddle cover.

I took a picture of the topside of the circuitboard because the Japanese website didn't show that view. Mainly, I was interested in knowing what the DIN-13 connector looked like so I could determine how difficult it would be to mount inside the guitar. There's a marginal benefit in buying a new DIN-13 female jack from Digi-Key since you'd probably have to remove the jack from the circuit board anyway. The circuit board's connector has a flat, square face with a space to drill tiny holes for mounting to a body plate. In fact, there are at least a couple of slots along the connector's body which could accommodate very small nuts for the screws.

To provide "straight guitar" functionality (in case the 13-conductor cable broke), the jack for the guitar's regular pickups could be set up so that in an unplugged state, the guitar's regular pickup signal would be routed to the electronics. Plugged, the signal would bypass the electronics and go directly to the regular pickups. 1/4" jacks are available which allow several different switching options (normally open and normally closed). I think this would also allow the use of two cables, if one wanted to keep the signal paths separate.

The potentiometer's value needs to be determined; from the Japanese text (and from a second disassembly), it appears to be a 50K B linear taper. Finding a suitable replacement should be pretty easy.

Other than that, it's mainly a matter of desoldering the original components and mounting them with stranded wire to the replacement components. The Strat's control area has plenty of room for the circuitboard. However, the most irreversible and drastic part of the process requires that you route your guitar's body for mounting the 13-pin jack housing. Altering the plastic scratchplate with extra holes is no big deal-- those can be easily replaced, but a guitar's body is a significant and more expensive part of your guitar. You could choose to mount the jack on the scratchplate but would lose some valuable real estate-- and it would look kinda dorky. That's one of the reasons we're considering moving the wart inside in the first place!

 

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