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Installing a GK Kit on a JTV69
by flabergaster on 2012-04-08 16:36:15.7180

Here's my line up:

JTV69 Sunburst

Variax 700 Trem in Blue with the external Roland GK3

Cort G250 with Roland GK-Kit-GT3 installed

Pod HD500

Roland GR55

I love my JTV69 and I much prefer the guitar sounds of the JTV/HD500, but the GR55 electric sounds are good too plus all the synth stuff. I just found out that our keyboard player is going to be out for several months because of a schedule change at work. I'm going to need to cover a lot more keyboard territory, so I'm considering installing a GK Kit on my JTV69.

I've done a bit of reconasance work, and I believe I have room for everything, but when inspecting the jacks for the VDI and 1/4 inch, I found quite a bit of circuitry on the 1/4 inch jack. I never plan to use this jack and I would like to terminate it internaly, and use it's position to install the 13 pin connector for the GK.  Here's my question: I may be dreaming, but is there any way to get a schematic, or at least guidance as to how to terminate the wires properly to simulate the jack without it having to be there?

I know that there must be some switching going on to tell the guitar when it is on battery, and to route the models and mags to the 1/4 inch. I always plan to use this guitar with my HD500 as the power source through the VDI cable, so the battery will be moot, and with the GK Kit and the GR55 I'll have built in redundancy in both directions should any of the above fail.

I know this will probably void the warranty but, I'm an electronics tech by trade, and I installed the Kit in my Cort G250, so I'm pretty confident in my ability to install the same in my JTV69 if I can just figure out what to do with the 1/4 inch output jack.

I know that I could go with the external GK. I just hate to ugly up my pretty sunburst, but at the same time I don't want to relegate my JTV to back up duty because I need the synth sounds to cover for the next several months. Besides, even though it's a pain dealing with 2 cables, it is really fun to be able to have the best of both worlds at my feet and fingertips. It'll be like having a poor man's version of Adrien Belew's setup.

Any other techs out there, or maybe some help from Line 6? I can probably reverse engineer it, but my undying gratitude to anyone who can save me the time and trouble.


Re: Installing a GK Kit on a JTV69
by johnnyayyy on 2012-04-08 21:37:54.7950

MarkCline wrote:

I'm pretty confident in my ability to install the same in my JTV69 if I can just figure out what to do with the 1/4 inch output jack.

I had a similar dilemma and solved the problem by leaving the 1/4" jack connected, popping it out of the Variax jack plate, and simply pushing it inside the body.

Re: Installing a GK Kit on a JTV69
by flabergaster on 2012-04-09 06:41:12.4960

Many Thanks! Exactly what I needed!

Re: Installing a GK Kit on a JTV69
by Kupsik on 2012-04-09 10:30:07.1130

Hi Mark,

if you succed in installing GK internal kit on a JTV69, please share some photos and little bit info how you did it with rest of us - where did exactly put GK's PCB, pots, knobs, if you did any drilling etc. I'm also thinking about this mod of my JTV-69 but I'm not so skillful, so I would ask my friend who has more experience with this and detailed info from you would be very heplfull.

Thanks in advance


Re: Installing a GK Kit on a JTV69
by flabergaster on 2012-04-11 07:12:54.7620

I'll try to do just that, but it may be a month or more before I get time to take it on. Plus I'm waiting on an ebay item to sell to finance the project.

It appears that there is plenty of room under the hood, and since I'll leave the GK hard switched to GK I'll only need the volume and a single spring loaded up/down toggle for bank changes. I think I'll either route a place on the lower bout below the pick plate, or if I get really brave, and am sure I want it there forever, I could mount them in the wood behind the existing knobs.

I'll keep a photo record when I get the time and the nerve to take it on.

Re: Installing a GK Kit on a JTV69
by Kupsik on 2012-04-20 10:38:56.0690

I have just ordered Roland GK-KIT-GT3. As soon as I get it, I will do some preliminary photos and measurements of cavities and I will try to find place for it (mainly for PCB) inside JTV69...

Re: Installing a GK Kit on a JTV69
by stevekc on 2012-04-20 11:00:49.1850

I'm interested in this too

I'm Elantric at

I used one of those ebay GK-3 Mountng rings from the UK for my GK-3 External install on my JTV-69

<a target=new href=" class="jive-image" src=""/>

Re: Installing a GK Kit on a JTV69
by Kupsik on 2012-04-24 09:57:11.0260

So I have recieved Roland GK-KIT. Roland's PCB can be placed in same cavity as Line6's one, but I need to find solution how to fix it here . Cable from Roland's pickup with connector is small enough to go throug hole for cables from Line6's piezzos. I haven't removed Pick guard yet, but I don't think there will be any problem with placing Roland's pickup correctly, I just need to make hole for cable, hopefully without any big drilling. Biggest problem for now seems to be where to place 13-pin connector - next to jack or next to digital connector? I will post more info during weekend, I hope to have more time for looking into it...

Re: Installing a GK Kit on a JTV69
by Kupsik on 2012-04-25 11:02:12.4560

Just one quick update, I found out, that it's possible to turn Roland's pickup upside down (Roland logo will be close volume pot) and reorder cables on connector from this pickup, so I will need only to make small hole from there to large cavity under Pick guard... Stay tuned for another info ;-)

Re: Installing a GK Kit on a JTV69
by flabergaster on 2012-04-27 15:11:34.5680

The mounting ring does make for a clean install, but from the pic it looks like it positions the pickup beyond the 20 mm maximum recomended distance from the pole pieces. It looks good but have you noticed it lacking anything in performance/tracking/model tone etc. ?

I may tackle mine next week. I'm still puzzling over where to put the 13 pin connector. I wish the jtv didn't have the trap door over the VDI connector. The hinge is in the way if trying to use the 1/4 inch jack hole. In stead of just enlarging the hole, it looks like the hole will have to shift away from the hinge. Hmmmmmmm ...............

Re: Installing a GK Kit on a JTV69
by Kupsik on 2012-04-29 09:26:49.6930

Another quick update - Since I'm not using battery for JTV (I already sold it with charger) I will use battery cavity for Roland's PCB. I will try to drill small hole from humbucker cavity into this battery cavity as a shorcut for cables from Rolands pickup and maybe for another staff (like cables from volume control) if I need it. I will also use battery "case" (don't know right english word) and put Roland's PCB into it instead of placing it into Line6's PCB cavity - it will be safer and also Roland's PCB fits there perfectly. I only need to replace battery cover with another plastic because I need to use that "hole" in the right side where you press cover to open it...

Re: Installing a GK Kit on a JTV69
by flabergaster on 2012-05-01 08:06:06.3010

I took some vacation time, so I finally accomplished the install. It turned out as good as I could have hoped. Please pardon the less than stellar photography I was using my Android tablet which isn't the best camera.

I did quite a bit of studying on Sunday before diving in.

Once I got under the hood, I found that there was ample room for the GK Circuit Board, but it is very busy under the pick guard. I decided to put the GK volume on the lower cut away as far forward as possible to keep me from punching it on those big Pete Townshend chords. I also decided to forgo the bank buttons or switch, and the Output selector. I can easily navigate banks and patches with the foot pedals on the GR55, and if you don't plug anything into the output selector header plug, the board thinks it is in the "Mix" position which is fine for me since I'll be running the JTV signal through the HD500. Here's some pics of my planning layout:



No matter how I approached it I couldn't find a way of adding the 13 pin while keeping both the VDI and the 1/4 inch. The 13 pin would have run into Variax Circuit board if I tried routing a location on the VDI side of the OEM jacks, and it would have been too low on the body if I'd put it on the 1/4 side, which would have had it pointing almost straight down.

I figured the only way was to replace the 1/4 inch with the 13 pin, which is fine for me because I can count the times I've used the 1/4 inch on no hands.

The next problem was to figure out how to do this. The OEM injection molded plastic jack plate is sculpted to the point that I would have very likely destroyed it in trying to alter it enough to be able to mount the 13 pin on it, so I took an old pick guard that I had from a Variax 300 that I had long since sold, and I fashioned my connector plate from it. It wasn't too difficult and I had enough material to make several tries if the first one didn't work out. Luckily the first attempt was fine so about an hour later I had this:


I was never all that fond of the trap door on the OEM model anyway.  I metered the 1/4 inch jack assembly, and though there are some capacitors, ferrites, and switching on the jack, I was able to determine that when the jack is empty, it is essentially as if the jack isn't there. So, I unsoldered the header from the jack assembly and taped it up.


Now for the scary part; Drilling and Wood Removal

I used a standard Dremel Tool that I picked up at Lowes and a saber action rotary saw bit to route out the compartment for the GK Volume, and to square the jack plate cavity so the 13 pin would fit:



Oh and I also taped up that little ground wire you see there that went to the 1/4 jack.

After testing to see that the jacks and the GK Volume pot would fit into place, I moved on to mounting the GK Pickup.

The GK Kit instructions say to mount the pickup as close as possible to the bridge pieces, so I masked and carefully marked the area. You may notice that I also trim the original upper mounting tab of the pickup, and redrill it. I don't know why Roland puts this extra 1/4 inch or more on it, unless it is the same piece as on the external GK where the wire exits off that end, and they don't want to retool the factory, so they use the same piece on the kit as well.

I decided to drill the cable hole first, so that I could lay the pickup flat on the top to use as a template for drilling the initial pickup mounting holes for accuracy. I determined that I would have to go at an angle to exit in the trem cavity for easy routing of the cable through the same hole as the Variax bridge cables into the circuit board cavity.

Here are 2 pics showing the entry and exit wound, and the angle of the entry:



If you're thinking that the header plug won't fit through that hole, you are correct. I have experience with this type of plug from my work as a radio technician. A straight pin or needle will act as  a pin releaser, so I wrote down the color code and removed the pins. All the pins grouped together was still too large for the hole when taped up, so I folded 1/2 of them back on them selves to reduce the girth when taped, and was then able to work them through. Pic:



Now to finish the pickup mounting. I found these nifty little inserts in the specialty fasteners in the drawer indexes at Lowes under Furniture Fasteners.


Unfortunately, I had to go to a different hardware store to find 6-32 thread machine screws with an allen head. I used an allen because all the pan head screws I could find were too wide for the mouting bracket and would bind against the metal cover of the pickup. I used electrical tape on the bits to control the depth of the drilling, and progressively stepped up from the eigth inch hole in the bracket to a size just under the thread width of the inserts. A set of calipers is very handy for this type of measurement. I would prefer a drill press for this, but I took my time and was able to freehand it. Here are several pics for this step:




As you can see, the inserts are recessed just below the surface of the top, which gives a resting place for the springs. Hint, the springs provided are too long for most applications, so take some side cutters and trim about 1/4 inch off each spring. This will also keep them from shooting across the room when you try to install them.


Ready to assemble! I have a staple gun that is made for captivating cable, so I put a couple under the springs in the trem cavity to keep the GK pickup cable from moving around any more than necessary, but loose enough to have some play if I need it.


Here's the electronics cavity with the board installed, and the newly fabricated jack plate installed.



A quick trip to a local music store for a nearly perfect match chrome knob, about an hour to set up, and intonate the guitar, and then set up the parameters of the GK installation in the GR55, and the job was done. Start time approximately 7:30 a.m. finished at about 2:30 p.m. plus about 2 hours of study and planning the day before.


If you've made it this far, thanks for hanging in there.  This may be more than a lot of folks would want to take on, but if you are good with your hands, take your time, and maybe read the book "Zen And The Art Of Motorcycle Maintenance" before getting started, the payoff at the end is too much fun!!!

Good Luck!


Re: Installing a GK Kit on a JTV69
by merman_96 on 2012-05-02 08:52:19.2330

Great pictorial !  I have done several gk kit installs myself, but never on a JTV. I have learned a few tips here too,( I'm going to Lowes to find those inserts today !!).

Thanks for posting.

Re: Installing a GK Kit on a JTV69
by Kupsik on 2012-05-09 11:28:32.4560

Hi Mark,

I like your work! I also managed to do my own instalation of GK-Kit. I used little bit different aproach. Since I don't need/use battery for powering JTV (I use it solely with POD HD500) I used battery holder and placed Roland's PCB there. I've also disconnected cables from this holder to have more room in the hole to cavity with Line6's main PCB because I've routed cables to 13-pin connector through there (friend of mine make longer for me, original were too short for my needs). I've installed Roland's pickup upside down (part with logo is next to pickup) because I like it better (I change order of cables from pickup to have them correctly recognised by my Axon 100 mk II and to have full compatibility with other gear if needed). I've routed cable from pickup under humbucker and then I've drilled hole from under the humbucker to cavity with battery holder to have shorter way for cable. I've placed 13 pin connector next to VDI one - I've decided to keep classic jack connectro in place in case I ever need it. Connector fits perfectly to cavity with Line6's main PCB, it sits right next to and little bit under main PCB, of course after some carefull drilling.

I've only used pickup without any other controls - no switches, volume pod, led. Now I'm working with POD HD500 midi capabilities to see if I can control everything I need on Axon with POD and then I will decide if I need any phisical control on guitar.

So my approach is little bit different than Mark's, in my opinion both have their advantages and disadvantages according to mine / Mark's preferences. I like to see more options how something can be done ;-)

Oh, and some pictures of course!







Re: Installing a GK Kit on a JTV69
by flabergaster on 2012-05-10 14:13:21.6660

Good Job!

There's usually several ways to skin the proverbial cat. The battery compartment looks like it was made for that purpose. When I work up some more scratch, I plan to get another kit to install on my Variax 700, and I think I'll mount the GK board in the battery compartment on that one.

I got to play mine in a live environment last weekend, and it worked great. I've decided that I really like the GR volume control on the lower cut away. It makes for really easy and comfortable access. And I've almost gotten used to bank/patch changes from the pedals on the GR55. It actually makes it possible to change banks while playing which is a plus.

It sure is a blast having the Line 6 and Roland sounds on the same instrument. I hope you have as much fun with yours. Let me know what you learn about midi-ing up the two pedals. I've got a midi cable standing by to do the same, but it is so hard to find time for tinkering.


Re: Installing a GK Kit on a JTV69
by litesnsirens on 2012-05-21 13:02:26.4170

I really like this idea and I am thinking of endeavouring on a project like this so I really appreciate the ideas and the pics.  I would like to get the GR55 I'm guessing if like Mark posted I add a volume pot for the GK pick up then using the two volume pots I could use one or the other or blend the two.  I am also wondering if I could use the midi from the HD500 to choose patches on the GR55 so that I only really have one device under foot so to speak. I could leaver the GR55 near the back of the stage.  Has anyone tried this yet?

Re: Installing a GK Kit on a JTV69
by player99 on 2012-05-21 15:50:08.7650

Why not use a GK3? Tape the pickup to the body and velcro the contoller to the back. Done in under 1 hr...

Re: Installing a GK Kit on a JTV69
by buge2 on 2012-11-30 11:55:22.8580

Hi All, I don't usually post stuff but ever since I got my JTV-69 I've been wanting to get midi onboard, rather than outboard, and there have been all sorts of inventive ways of doing it. But I'm not that hands on so I found a guy who is, told him what I was after, and I've got the perfect JTV-69 with onboard GK3, midi volume know, mixer mini switch to switch between JTV or midi or both, and S1/S2 sprung miniswitch to change patch or bring up the ( in my case ) GR-33 tuner etc. I'm over the moon ! Here's a pic:jtv midi.JPG

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