Roland GK-2 Wiring Question

[mdavis072]

I recently bought a GK-2 pickup with a GR-30 synth off of craigslist and (surprise) the pickup isn't working. I opened up the pickup and saw that many of the copper wires from the coils were not soldered to the board. Does anyone know how I determine which solder points to resolder the coils to?

[sumgai]

md,


Hi, and to the NutzHouse!

I've been using and monkeying around with GK pickups and all manner of Roland products for something like 16 or 17 years, but in all that time, I've never thought to open a pickup and document where everything goes/went.  Sorry, but I can't help you directly on that one.  In fact, I just spent some time searching the web, and no one else has thought to post any images of the guts, either.

As to figuring out where those coil leads go, it's actually pretty simple to use a multi-meter to do a continuity check.  But let me ask you this - when you say that the pickup isn't working, do you mean each and every element (one pair of coils per string) gives no signal?  Or do one or two of them work?

But more questions need to be asked: Are you certain that the GR-30 is set up properly, etc.?  Are you certain that the 13-pin cable is good? Some of those have been known to become flaky over time.  And just for drill, is this your first foray into the world of guitar synths?  

Don't worry, several of us here are into this kinda thing, so you're bound to get answers sooner or later.  Maybe even some correct ones, wouldn't that be a hoot?!

HTH

sumgai

[mdavis072]

Thanks so much for the warm welcome and your help sumgai. I would have been surprised if you would have been able to find a picture online haha because I've been searching around to no avail. This is my first experience with guitar synths, but I've done a fair bit of research and only took the pickup apart when it was my last option.

The initial problem was that all of the strings were being picked up except the high e. First I factory reset the GR-30, then sprayed the 13 pin connectors with some contact cleaner. Then I bought a new cable, because I know that those can be the source of a lot of problems, but that didn't fix the problem. After that I was so frustrated that I decided to try to take the pickup apart, which tore all the coils from their solder points so now of course none of them work. I truly suspect that may have been the source of the initial high e problem though, and I'd like to resolder them to check. 

[sumgai]

md,



I'm not sure what you did to tear the coils out of their base, but what's done is done, so let's see what it'll take to fix it.

I don't have a 2A in front of me, in fact I no longer have one at all, it went away with my last guitar... all I have now is a GK-3, and it's still in the box, to be installed at a time-and-date to be named in the future. (An in-joke, here in the NutzHouse). Which means of course that I can't get down to the nutz and boltz for you, but we do have another member here who I'm sure can help in some small way. Let's put out a call to....

HEY gumbo! Can you help a fella out here?!

I'll PM him and let him know he should drop in, we'll see how long it takes.


Here's a thread from 10 years ago, wherein I took an external GK-2A and stuck it underneath the pickguard. Ask any questions either in that thread or here, if you got 'em.

guitarnuts2.proboards.com/thread/451/killin-time

sumgai

[mdavis072]

Luckily I do have a multi-meter laying around. Could you give me some more information on how to do a continuity check to figure out where the leads go, or link me to somewhere with that information? I can't seem to find anything by googling around. Thanks again. 

[gumbo]

Evening All...
.and thanks for the heads-up sg.

Sorry I've been a bit quiet lately; a bit of stuff going on Down Here that has been taking up my time.

7.30am Monday here and a full day ahead again, but will get back here in about 12 hours when the dust settles a bit.. ...I'm sure we can sort this out.

g-f-b

[sumgai]

md,



When gumbo says "down here", he really means it - he's in Adelaide, South Australia.

An old friend of mine from even before the days of The NutzHouse, he's also into Roland GK stuff. Let's see what happens here....

Oh, and be prepared - we don't call him the Master Thread Derailer for the heck of it!!


(g-f-b is short for 'gum for brains', which he devised himself - don't blame us!)







sumgai

[gumbo]

(g-f-b is short for 'gum for brains', which he devised himself - don't blame us!)


...ha!


talk a bit later tonight...just got home (6.30pm) and food is calling

[gumbo]

OKAY!

Here's the pin-out for an ancient GK2A pickup straight from the Gumbo Archives...

Let's first acknowledge that the HIGH E is the 1st string, and the LOW E is the 6th string.

the Gk2A pickup has six 'mini-humbuckers' each of which SHARE a common return wire ([thin]BLACK.

the GK2A pickup has a SEPARATE GROUND wire, (usually [thick] BLACK)

ALL THE WIRES EXIT FROM THE PICKUP ADJACENT TO THE SIXTH STRING

1st string feed is BROWN

2nd string feed is RED

3rd string feed is ORANGE

4th string feed is YELLOW

5th string feed is GREEN

6th string feed is DARK BLUE

...that's what you've got to aim for with your trusty multimeter..

HTH

call me in the morning if you need more info....

[gumbo]

...also worth noting that overall improvements in tracking can be obtained by potting the pickup...

Read:

www.vguitarforums.com/smf/index.php?topic=23268.0


AND READ THIS ONE COMPLETELY & CAREFULLY:

www.vguitarforums.com/smf/index.php?topic=3132.0

...most 'contact cleaners' remove oil/grease/debris, but NOT oxidation, which is what kills 13-pin DIN connections on a regular basis.
...we are talking MINISCULE signal strengths from a GK pickup, which are being fed to pre-amps in the onboard PCB before they can do anything with or for your GR-30.
All (yes, ALL) connection points in the chain can benefit from Caig's DE-Oxit


....also JOIN that Forum; it is Central Station for all things Roland GK..

Cheers

Peter ...I'm "gumbo" over there too....

[blademaster2]

I am just jumping into this thread, but I am shocked at the poor quality workmanship of that circuit board.

It looks like someone has messed with it, or that it is a counterfeit product, or both. I have never seen such poor work on a commercial product. I would investigate its authenticity.

[sumgai]

gumbo,



Err, the OP wanted to know exactly which eyelets on the circuit board are supposed to have the signal from the mini-pickup's 'hot' lead(s), and which eyelets should be the 'ground' lead (but that's common, so it should be easy to determine - there should be a uninsulated wire running through several eyelets on one side).

---

bm,


What you see is the result of the cover being taken off in what the factory would call "an improper manner", thus causing the damage you see. Trust me, that's a genuine product, it's just seen better days, that's all.

---

md,


I was hoping that g-f-b had a photo or two, but it doesn't look like it. Take some more images, top and bottom, and maybe something will become obvious that we can then direct your efforts more fruitfully.








sumgai

[blademaster2]

Okay, improper removal way well be the case, but the splattered mess left by the flux and the poor routing of the fine transducer wires gives me the shivers. Roland's manufacturing service provider would never pass inspection in my industry.

The similarly-fine wire on single-coil pups always looks far better than this.

[gumbo]

sg:

Sorry, but I don't have a GK2A in pieces to answer that question.. ...hence the form of my reply
I would have thought that it was reasonably easy to trace which solder point was which as I presumed the PCB connection points for the cables were still intact (left of pic)
...simple connectivity test from there with a multimeter ?? No ??


bm:
What we're looking at here is a 25+ - year-old bit of kit that has seen better days, let alone what has happened to it recently


md:

FWIW, there are a NUMBER of things that could be disrupting the connection between the pickup and your (eventual) amp, including the 25+-year-old GR-30...all have to be carefully worked through.
After-market 13-pin cables can also be problematical, as many are sold (like on eBay) that are in fact NOT COMPATIBLE as they are actually Kenwood Car Stereo cables that have the wrong internal connections...these can in fact do damage to your synth unit as well by mis-connection of the 7-volt supply that goes from the GR-30 to the GK2A...


More reading and understanding is required before hacking into stuff... Let's all take this slowly...

[mdavis072]

Thanks everyone for your continued help on this. Sorry for the delayed response, I've had some law school exams which apparently take priority over messing around with guitar gear. 

Thanks for coming by and trying to help gumbo. I signed up for vguitar forums and searched through the threads there (and even downloaded an extension to let me see old photobucket pictures) and couldn't find any close ups of a GK2 board. I understand that I can use a multimeter to to a continuity test and find out where to solder the coil leads. But I'm pretty new to this wiring thing (clearly), what I don't understand is literally how to do that. As in, where to I place the multimeter test leads in order to determine which of the three solder points to use? I've only ever tested standard pickups before. 

[reTrEaD]

Apr 24, 2018 11:38:24 GMT -5 mdavis072 said:

As in, where to I place the multimeter test leads in order to determine which of the three solder points to use?

I think the next step might be some better pics of the printed board. Take one directly (not at an angle) from the top side and another with the board flipped over and a straight-on view of the back side. Work with the illumination and see if you can get images that clearly show the foil pattern.

I sort of expect there will be a pattern here for each of the six coil pairs.

One pad will connect the end of a coil to the 'hot' lead for that pair.
Another pad will connect the end of the sister coil to the common ground.
Yet another pad will serve as a series-link between the two coils of that pair.

With some good images, we should be able to map this out.

[gumbo]

reTrEaD is fairly-well spot on about the pickup's wiring basics..
...I'll get back with a bit more verbage later.

My main point (will be) that there needs to be a check out of the electrical continuity between the multiplug on the end of the pickup connection cable and the solder points on the pickup PCB before going anywhere near a soldering iron...that's all got to be proved viable first otherwise you could be wasting a whole lot of fruitless time and energy.

...talk later.

[gumbo]

Hi md:

Here's what I wrote this morning...

I'm one person who understands well how other things in life get in the way at times… !

The basis of a continuity test is to establish an existing electrical 'pathway' between two points:
In your case, you are trying to find where that pathway exists between the colo(u)red wires connected to the end of the pickup PCB and the corresponding solder pads that will be attached to the individual pickups.

The way to go about this is to use your multimeter set to "Ohms" so that it is measuring the resistance between its two probes. When the two probes are touched together, you get a reading…have a look at this video:



…there are many more videos on the Net, but some are unnecessarily complicated in the way they go about it..

First, UNPLUG your pickup from the main PCB of the GK-2A.

To find the connection points for the feed to the (say) 1st string pickup, place one probe on the solder pad that is attached to the BROWN wire.
Place the other probe (in turn) on each of the two pads adjacent to the 1st string pick ups..remember that you are dealing with the two separate coils of a mini-humbucker…

When you get a reading (other than "I"), you have established which solder pad is connected (via the tracks in the PCB) to the BROWN wire.

Using the same method, you should be able to establish that the remaining pad adjacent to the 1st string pickup should be connected to the BLACK (common return) wire.

Make a drawing of this as you progress…do NOT trust it all to memory.

Work your way along the pickup PCB in this way and you should be able to establish viable connections between the various individual pickup solder pads and the connection points of the colo(u)red wires at the end of the PCB that disappear into the shielded cable that goes back to the main GK2A PCB via the 8-way multiplug. Use the listing in my earlier post to see which wire should be connected to each pickup solder pad.

Once you have done that, do a FURTHER test of continuity from the solder pad of each colo(u)red wire to the appropriate connection pin in the multiplug at the end of the cable…to ensure this part of the circuitry is also working properly.

If you can trace the circuits to each solder pad in this way and also within the connecting cable and make sure you have a viable connection (in other words, there are NO breaks in the tracks of the pickup PCB, OR in the connecting cable itself), you can go ahead and (carefully!) solder the individual pickups back to the PCB.

If your testing indicates there is a break somewhere, you will have to fix that first…either by soldering a small jumper wire BETWEEN the pad for the offending col(u)red wire and its appropriate pickup solder pad, or fixing a break in the actual connecting cable.

If you can't correct any such problems, it is a matter of abandoning the entire project and purchasing another complete pickup somewhere..


THIS EVENING I pulled apart a (brand new!) GK2A, which is slightly different to your GK2… (thought I had a GK2, but no…. )

It doesn't have the central row of solder points, which reTrEaD correctly assumes (I assume too!) are for the serial connection of the pair of coils in each mini-humbucker…it just has two connection points per 'bucker.

You should be able to establish that those central solder points in your pickup PCB don't in fact go anywhere by just checking for continuity between them and anything else…

Apart from the 496 photos I took (you don't get them all!), I also pinned out the GK2A PCB, and now post a photo of the result…I think it's probably reasonably safe to assume this is pretty close to what you will find when you do your own testing.

HTH…good luck and continue to ask questions.. ..happy to help when I can (and am awake!)

Cheers from Oz,

Peter

[sumgai]

HOLY JEEBUS! All hail the gummy one!!


I want you all to know that this is, without a doubt in anyone's unmilitary mind, easily the longest post that g-f-b has ever written, anywhere on the innerwebs. Not only was it informative in the extreme, he did it without once derailing the thread!!!! 1,000 Exalts to you, gumbo!

Or, in current ProBoards parlance, this will be the second post for which I will issue a "Like".

md, I think your worries are over, as far as what to do and how to do it are concerned.  But as usual, questions are answered freely.  Sometimes even correctly.

sumgai

[mdavis072]

Thank you so much for your help gumbo, you were absolutely right about which solder points to connect to. I confirmed all of the connections, and then soldered the coil leads to the solder points on the board. I then plugged in and...nothing happened. None of the coils are picking up the vibrations of the strings, even with the sensitivity all the way up to 8. Here's the thing though, if I tap on the uncovered coils with the tip of a screwdriver, the GK-30 will usually pick up a signal from all 6 coils pairs, so I know that a connection is making its way through eventually. Maybe the screwdriver is creating a circuit? So then I decided to test the connection between the actual pickup coil itself and the corresponding colored wires. I found that even though there is a reading between the colored wire solder point at the end of the board and the solder point for each pickup, there is not a reading between the colored solder point and the pickup coil that is supposed to be wired to it, or even between each individual pickup's solder point and the pickup itself. So to use your diagram, when I place one test lead of the multimeter on the red wire connection point, and the other test lead on the bottom 2nd humbucker coil, there is no reading. There should be if the humbucker is properly soldered to the PCB, right? This leads me to conclude that although there is a good connection throughout the board (so red with red and 1-6 with black on your diagram), there is not a good connection between the coil itself and the point it is supposed to be soldered to. 

Am I missing something obvious here? Like I said I'm not very experienced with this stuff, I really just felt I had nothing to lose by trying. Connecting the coil to the solder point just involves taking a strand of the thin copper wire from that coil and connecting it to the dot of solder in question, correct? 

[gumbo]

md:

When you say "the pickup itself", are you meaning the pickup magnet pole-pieces ??

There is NO electrical continuity between the WINDINGS of the pickup and the pole-pieces that you can tap with a screwdriver tip....

...that's a magnetic field that does that job..


Yes, it is the winding that you connect to the solder point..




BTW, which jack on the GR-30 are you connecting to your amp ?

[sumgai]

md,


The problem here is not obvious, but it can be cured... with lots of patience.


The wire used for winding the coils is very tiny in diameter, something like 42 gauge, IIRC. The problem for you, and most beginners, is that all pickups, regardless of wire size, use a coating of insulation on the wire itself. IOW, the windings don't touch each other directly as the wire is wound around the bobbin - if they did they'd short out.... and carry no signal.

The lead ends that you soldered into the holes should have been scraped clean of insulation. This is actually nothing more than a coating of shellac (or something similar), you can remove it with gentle strokes of a screwdriver blade, preferably using a side of the blade. Knives tend to cut the wire, regardless of how little effort you put into it.

Once the insulation is scraped back a quarter inch, you can solder it into the hole, and test for continuity. Just try one pickup/hole at first, using the whole process I just described. If that tests out good, then do the remaining five units.


Now....

Testing.  Once you have a single pup's leads scraped, soldered in place, and theoretically ready to go, do this:  Set your multimeter to Ohms, place one lead on the 'hot' side of the circuit at the very end of the cable that goes into the wart.  (Take apart the wart, and unplug the cable, it's not hard.)  Place the other test lead on the signal ground (black) lead of that same plug.  If you don't read something between 3 and 5KOhms, then there's a problem.  (It might be a bit lower, I don't recall the exact value....)  Go back and review your work, and where you connected your test leads.  (Did you associate the wrong wire color for your "repaired" pickup?)

And finally....

gumbo's question about which jack you're using to output the signal to the amp has some merit, but you did say that you can hear it when the screwdriver pops off of the pickup coil.  The signal path is good.

Still and all, these little buggers are not sensitive in the normal sense that we usually associate with pickups. Those are tiny coils, and they generate very little signal by themselves. This is exactly why the cable carries plus and minus 7vDC from the GR-30 up to the wart - to supply little amplifiers, one for each pickup. So, that means that you have to get a string pretty darn close to the pickup element in order to make things work. A screwdriver test isn't guaranteed to work because the amplifiers I mentioned also have hi-pass filters involved, to quash crosstalk between the pickups themselves.

It's not easy to fix and test these things, but like I said earlier, with a carload of patience, it can be done.

HTH

sumgai

[gumbo]

"And finally....

gumbo's question about which jack you're using to output the signal to the amp has some merit..."


Now THAT'S got to be worth a few derailment points, surely ??

[gumbo]

md:

The correct position for a GK2A & GK3 pickup (don't have anything on the GK2, but let's assume it is the same..) is:

NO MORE than 3/4 inch away from the bridge saddles ...to minimise cross-talk between strings

NO MORE than 1/16 inch from the underside of the strings when you fret them at the highest fret ...because (as sumgai says) these tiny 'buckers are just that, and need all the help they can get

...the height setting IS CRITICAL to get the thing to work.... and depending upon the guitar in question, can take a bit of playing with things to get it right..like playing with bridge saddle heights and neck shims



If you've spaced the GK2 at the same height as a 'normal' magnetic pickup, that could be 9/10 of your problem

HTH

[gumbo]

Having re-read all of the last few posts, and in the absence of anything further from the OP...

...one does wonder however, that if the GR-30 is "picking up a signal", how is that being substantiated by the OP? If that is by means of the line of 5 LEDs on the main display...I would think (no I haven't un-buried one of my GR-30s yet!) that those 'sensitivity indicators' would light up, even though the OUTPUT of the GR-30 would go nowhere if the lead to the amp was plugged into "GUITAR OUT" and not (LEFT) "MIX OUT"...and that only works properly after booting the GR-30 while holding down pedal 1...

The OP needs to read page 12 of the Owner's Manual...

That's it for tonight....someone else can take over this bag of worms while I rest my derailing head....

g-f-b








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