GK-3 - Mods - Distance to string, radius mods, potting

Started by Elantric, February 25, 2008, 09:09:59 PM

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montyrivers

#25
Does anyone else think this is the most infuriating and poorly designed feature of the GK 3?  I'm not saying that i'd prefer they didn't have it at all but the little screw keeps wiggling out and even after I adjust it all the way I still have to put a piece of tape over one of the hex magnets to get the adjustment to stay put.

Do they make a plastic cover for the GK3 or something like it?

Has anyone else gone through this kind of odyssey?  What did you do to set it up properly?

PS:  I can't speak for the GK 3 kit, I just have the aftermarket version.
I should also add that my guitar has an extremely "flat" neck radius compared to a lot of other guitars out there.

Elantric

QuoteDoes anyone else think this is the most infuriating and poorly designed feature of the GK 3? 

I agree!

On Gibsons, I prefer the Yamaha G1D (same as Axon AIX-101) by a large margin due to its tighter pitch and flatter radius compared to any Roland hex PU, but these are getting rather scarce in the used channel.


bgflex

The Dean EVO has a very flat radius so that when the GK-3 is adjusted properly for the middle strings, the outside strings remain at too great a distance from the pickups. How can the pickup be adjusted to match this almost flat radius?

Elantric

See post above -

I recommend the Yamaha G1D or Axon AIX-101 for flatter radius fretboard guitars.

The Roland GK-2A, or GK-3 can be customized for the flatter radius, but this takes great skill, and not recommended for the faint of heart.

tado921

#29
The day before a gig the A string on my GK-3 became intermittent. When I wiggled the cable at the pickup end it would cut in and out. I didn't have the cash to go buy a new one, and I new it would never be repaired or replaced in time, so I decided to try and fix it myself. I took a few pics for reference, and am posting them here in case anyone else wants to give it a try.

A word of caution: The internal parts are small and delicate. If someone decides to try this, be gentle!

OK, the first thing I noticed was that there was a small screw missing that holds this little cover in place. I had the pickup mounted with the cable above the strings, and I assume my playing had worked it loose. So, step 1 would be to remove this screw.



Next we have to get the top cover off by lifting these little tabs on the back. I used a small jeweler's screwdriver to gently pry them up. Do all of them on both sides, the arrows are just for reference.



Once the tabs are lifted, the top cover will lift off easily.



Now we have to get the backplate off, which is a bit tricky. The pickup is held in place by two tabs on one end, and some glue on the other. First, lift one of the tabs (red arrow), but do not pull it all the way back. Only do enough to get the PCB loose. It is plastic and may break off if bent too far.

Next, you have to very carefully pull the pickup away from the glue (yellow arrow). It will come loose, just use steady pressure and don't force it.




Now I can access the back side of the PCB to resolder the wires. Upon inspection, I could see that other wries were beginning to wear out, so I needed to resolder them all. Fortunately there is plenty of extra cable, so I stripped back some of the outer jacket and reworked them.



Note: These solder connections and wires are very small. If planning to do this, make sure you have the right tools or you could burn this PCB up, as it is very thin. I am an experienced electronics and soldering technician, with professional soldering equipment at my disposal. A 20 watt Radio Shack iron my be too much for this work, proceed with caution.

Once the soldering was done, I reassembled the pickup and remounted it, reversed this time. Everything worked perfectly, and I was back in business. This was about a month ago, no problems since. Maybe this will help someone out.

Tad

tado921

Forgot to add that you will also have to remove the pickup height adjustment screw to get the top cover off.

Elantric

#31
Excellent Post!!

Thanks for sharing.


BTW

Now everyone can see the actual individual pickups inside a GK-3.


These can be used to build a custom Pickup with different spacing and Radius to match your instrument.


BTW -Schematics are here:
https://www.vguitarforums.com/smf/index.php?topic=73.0

tado921

Thanks Elantric  :)

Also, I forgot that I drew a schematic of how the PCB is wired. The board is labeled with the wire color for each solder joint. I remember someone asking if this is a seven wire cable, here's the answer. Black is common with each wire going to an individual pickup. The view is from the top (component) side.



Tad

ntblade

Quote from:  tado921 on October 01, 2011, 07:57:52 AM

Also, I forgot that I drew a schematic of how the PCB is wired. The board is labeled with the wire color for each solder joint. I remember someone asking if this is a seven wire cable, here's the answer. Black is common with each wire going to an individual pickup. The view is from the top (component) side.


You'll have noticed that the colours correspond to the resistor colour code numbering scheme!
:)

gumbo

#34
Thank you tado921...your detailed post much appreciated!  :)

...and ntblade!
Read slower!!!   ....I'm typing as fast as I can...

gumtown

I had to do the same repair on a GK-3 i had brought from an e-Auction.
Someone had replaced the screw that holds the cable cover/support with one that was long enough to pierce right through the cable.
I had to chop back 25mm off the cable and resolder the whole lot. (successfully).

So what i am eventually pointing to is.. watch out the replacement cable cover screw is not too long. ;)
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

Eight_Stringer

Hello All,
            Just following on from the excellent work of this thread,  bought a few used GK-2 and GK-3,  the later suffering from the dreaded long retaining screw ( had this on 3 units to date ).  This one had the owner try 3 times with a fastner that was longer than the complete depth of the pickup assembly,  ie 3 holes in the thin PCB. Once i work out how to include pictures and repair process will do so.

BTW the individual pickups are humbucker wound from what i observed so far.  Regards to all.
   

tado921

QuoteBTW the individual pickups are humbucker wound from what I observed so far.

Interesting, they look like single coils to me. What did you see that gives you this impression?

Eight_Stringer

The pole faces on each string pickup are magnetic North and magnetic South facing the string over it. The phasing of the TWO wound coils looks like a humbucker connection scheme to my failing eyesight. Have a flux meter to quantify the actual field strength of the poles, inductance meter to quantify the inductive reactance value also on hand. DC resistance also will be measured.  Post this data here for reference material, over the next week or so. 

  What i need some assistance with is including a few pictures in the post,  tried the usual,  not obvious to me how to include pictures?  Regards

gumbo

Eight Stringer..

Hit "Attachments and other options" below the text panel in 'Post Reply'...

Thank you for your work on this subject..I look forward to seeing your test results and pics.  ;D
Read slower!!!   ....I'm typing as fast as I can...

tado921

Ah, I see what you mean. Good catch, your eyes aren't as bad as you think. :)

Eight_Stringer

#41
Following on from the good work by various contributors,  perhaps the following is of use.

GK3 pickup i purchased was damaged as mentioned previous.  Disassembled the hex pickup and the signal conditioning assembly. Made a working hand drawing of the operation ( schematic ), for the GK3.  There are a number of differences from the GK2A schematic.  Not just a simple mechanical makeover as it suggests ( being plug compatible GK2A and GK3 ).   If this information has not been covered previous then i will post it here as interest demands. Shout me down if any information is not correct.

Basic Hex pickup information.

DC Resistance  ( per pickup )  is 96 Ohms.

Inductance Value is 330uH ( micro Henries ).

Flux per pole face is 700 Gauss or 70 milli Tesla

Looking on top of the hex pickup with the cable entry on your right, North pole is top and South pole is bottom.  The two coils per string pickup are humbucker connected, to my best knowledge.

  Below is a damaged very thin substrate when incorrect fastener was inserted 3 times, extensive damage to the pcb.   Use a 0.1m/m copper tip 18Watt 24V pencil soldering iron for the repair. Connection to the pcb and incoming blue wire will be either Kynar ( teflon ) wire wrap wire or a strand of multistrand wire.  You will not get too many chances to solder the damaged area before the fibreglass FR4 laminate burns and delaminates.  Read,  not a task for non trained people. Though possible with guidence and care,  we all started somewhere.


Eight_Stringer

Quote from:  gumbo on October 10, 2011, 06:22:02 AM
Eight Stringer..

Hit "Attachments and other options" below the text panel in 'Post Reply'...

Thank you for your work on this subject..I look forward to seeing your test results and pics.  ;D

  Thank you gumbo,  was obvious,  just not to me. Old age....once we were warriors.. :). Regards.

gumbo

Eight_Stringer..

There are numerous things that escape me and my 63-y-o eyes... ::)    ...don't feel bad about that!

Thanks again for your work on this..there are some very useful facts coming out of your explorations..

..and I would certainly be interested in seeing the schematic drawing when you get a moment..   ...please!

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

Eight_Stringer

Further information on the internals of the GK3 control assembly. Post the repair pictures over next day or so,  for the magnetic sub assembly.

  There is nothing trick or exotic used on the control pcb.  Many of the parts are available through better supply houses. HTH and regards.

   

Eight_Stringer

Thank you Elantric for the information,  the GK2 schemtic is very helpful.  Just about to draw the switch control section for GMS control ( Guitar/Mix/Synth ) GK3. This switch is a 4 pole,  2 ( 3, centre off i believe ) way  device on the GK3. Did see a resistor net which now ( from your timely information ) is the voltage divider arrangement to produce the 3 analog control levels for external processing, on pin 9. 

  There is however many differences between the GK2 and GK3 circuits that comes to my attention so far. Simplified schematic of the GK3 will touch on the differences noted.

  Appreciate your timely help and information. Regards.

gumbo

Hmm...

Will have to have another look at the PCB in my GK3 internal kit too...   I see where you are coming from (and to!!) with this...  perhaps we are lucky (??!)  to be able to buy the internal kit for about AUD 175 Down Here at the moment...  for me this is reasonable value when I think about the various bits that the kit can 'donate'  ;D  to other little pet projects I've got going at the moment..

In my case I find the size and arrangement of the kit components far more adaptable to custom installs..let alone the notable absence of a Fugly piece of plastic to get in the way of most other things... ;)

I think that all the details that are slowly emerging in this (and related) threads is EXTREMELY useful and important..


Thank you to everyone concerned!   :-*

Cheers from Here
Read slower!!!   ....I'm typing as fast as I can...

Eight_Stringer

Hello gumbo,  am located NSW! You have a great price on the GK3 kit for AU$175, am somewhat perplexed how,  given i pay near that for used/damaged ones,  grim face.  Bargain considering EMG's run $150-200 for active PJ's.  My project is not so much lower cost as the OEM,  rather an effort to produce a versatile kit for the the basses and guitars here, which can be customised easly,  and others to have a choice of setups.

  Started on the GK3 schemtic capture task,  little hesitant to go flat out if the factory schematic is available as per Elantric helpful responces to date. One way or another the schematic will be available before too long.

Regards.
   

Zummooz

Hi Eight_Stringer  ;D
I'm in N.S.W too & you can get that GK-3 kit here ...
http://www.turramusic.com.au/Pages/CategoryList.aspx?CAT3ID=1129
I bought a few from there ages ago, thinking they were on special.
But still have that price of $175

Cheers Zum  ;D
The  Fact  Is......"We  are  all  tactile  creatures  &  physical  interaction  has  always  been  a  big  part  of  making  music"

Eight_Stringer

Am obliged for the information Zummooz,  all noted.  Look pretty silly paying close to that for a damaged GK3, never mind,  good will come from the repair of the damaged item.  Drive the new project,  knowledge is all at times.  Regards.