KP3 screen issue + foot pedal mod

[wax]

hey there - first post - serious problem - please excuse my english

so, the problem is that the touchpad of my KP3 classic doesn't react anymore...I already took it apart and I managed (however) to get it back to work - I cleaned the contacts of the thin 4-pin cable but now I can't bring it back to life again
I wobbled a bit on the contacts and even the wire looks alright...

I just wanted to make sure that replacing the screen would solve my problems cause I just got the news that a new screen will be 52€ and another 10€ for shipping (...wtf?!)...

Anybody had this issue before? Anything else I could check beside the wire-screen onnection?

Also... Isn't there a way to get such screen directly from a manufactor or even some electronic store? Looks like some "not so special" part to me?

Last thing...

Since I got the machine open up I wanted to replace my FX RELEASE - fader but KORG is charging 24€ for a replacement fader - . -
it's just a regular slide potentiometer (ALPS?), which is like 3€ at your electronic corner store - soooo... before I buy the expensive screen from Korg I'd greatly appreciate if anyone could tell me the model name or any secifications of the TOUCHPAD and the FX RELEASE FADER - there sure must be a cheaper way to get this fixed....?!


thnx!

[bradkorg]

1) Do factory reset first:
http://seventrumpet.com/how-to-reset-a- ... -settings/

2) Do pad calibration, use search/google kp3 pad problems/threads:
http://www.korgforums.com/forum/phpBB2/ ... hp?t=25777

http://www.korgforums.com/forum/phpBB2/ ... ht=#549345

3) Download Service manual:
http://elektrotanya.com/korg_kp3_sm_ver ... nload.html
-See service manual for repair diagnose etc.
-Do the service TEST procedures, Follow which step failure etc.
-Partlist for regular electronics replacements etc.

4) Touch Panel/Pad itself is a 2 capacitive foils layered on glassplate.
If there is no visible/mechanical damage on the Touch Pad and the connector/pins than the problem/defects is in the PAD electronic circuit.

-Use a multimeter to measure the electronics etc.
See service manual: Touchpad outputs PAD1/2/3/4 to PAD circuit transistors Q3/Q4/Q2, IC18-A/B, resistors R231/R230/R229/R237.

-If above Touch Pad and PAD circuit are good, than it could be anything defect so many other CPU/ROM/RAM chips/IC;s etc. then send to KORG repair.

5) Maybe on ebay you can find replacement electronic etc.

[wax]

Wow... very precise - thanx a lot! Will do the suggested tests!

[wax]

Ok - I'm through the list and still don't got it working - so sad as I need the KP3 everyday...

i did all the software stuff (reset, pad calibration ect.) but it just confirmed my assumption that the touchpad(-wire?) is the problem - i had to shut down the unit during the pad calibration cause the pad wasn't reacting - i know it's highly forbidden to do so but which option did i have?
unit seems to be fine though...

also i checked the connections going from the plug of the touch pad wire to the mentioned transistors and resistors - all fine.... i couldn't find a way to check the wire of the touchpad - plug connection since it's covered with foil - too bad cause this is what i actually need to know... any tips on how to check that connection? i don't wanna spend 60€ on a part i might not even need.. :/

side note:
there are replacement screens on the market ( canada ) - but they have the wire at the wrong position... d'oh!

i'm very frustrated - close to send it to KORG and eat toast with ketchup for a month...

[bradkorg]

Yes, it's always a gamble with electronics to find out what parts are exactly defective.
Especially when you don't have spareparts/tools for diagnoses like in the service/repair centre, they can swap/test with another touchpad etc.

And there are "many" KP3/KP3+/threads with touchpad problems (see recent KP3+ LED problem thread), it seems there's no feedback from people who have replaced the touchpad themselves that solved the problem, seems they just send it to dealer/korg repair.
If the repair costs around the same for a used KP3, you better just a used one and have some spare parts then.

-Normally If the touchpad just suddenly stops reacting, while KP3 is in operation, while you're rubbing it with abusive force or spill water on touchpad.
Then more chances is that touchpad is mainly defective caused by heavy wear and tear, the foils PAD1/2/3/4 signals paths could break or disintergrates etc.
-If touchpad stops working from a cold start/power on/or repeatly power on/off cycle too fast (cold/heat changes too fast will damage electronics faster), while last day/time it was still working fine.
Then more chances are the driving electronics transistors/resistors/ic's is (also) damaged.

1) You can try to make better chance that only the touchpad is defective by:
-Use a multimeter/ better with an oscilloscopemeter to measure if there's is voltage/Block waveforms signal changes on pins CN2 (possible visble pins on the backside of the white connector): PAD1/2/3/4 while KP3 is ON (with touchpad normal connected etc.) and touch/glide the Touchpad to give signal changes.
See service manual: I think PAD1/Top have (variable) driving +3.3V /superimposed-waveforms running through/to PAD3/Bottom and PAD4/Left have (variable) driving +3.3V running through/to PAD2/Right.
-When touch/glide the touchpad, on all PAD pins should give changes in voltages/or waveforms clocks, especially PAD2/Right and PAD3/Bottom these gives main signals to CPU.

2) There is (great) changes in voltage (drop) on PAD2/PAD3 when touching/gliding the touchpad, than more chances are the PAD circuit and/or the CPU etc. electronics are defective.
3) No voltage changes on (all) PAD2/PAD3, than possible only the Touchpad is defect.

-Do your bet!

[wax]

haha.. thanx man - i almost gave it up but you're spreading some hope.

Will check the voltages of the 4 pad pins asap... and IF they don't change voltage I might risk a blind shot and order a replacement screen ...! i been cool with the idea of getting a used one and modding the broken one - always wanted foot pedal access to the loop banks... also - u think it's possible to replace the touchpad with 2 potentiometers or doesn't the screen work like a resistor?

also korg is doing free checks, all you need to pay is the shipping - maybe i should go there - just like the other that ended up frustrated.

gotta check voltage first though... so, thanx again brad!

[bradkorg]

No, not that simple resistance won't work, it works with Capacitive variances that changes the trigger/proccessing blockwave Frequency from and return to the CPU.
Ofcourse if you can pay/find an electronic designer, an joystick-potmeters resistance to capacitance converter circuit can be made.

See the touch capacitive principle:
http://www.pcbheaven.com/wikipages/How_ ... works/?p=1
http://www.pcbheaven.com/wikipages/How_ ... works/?p=2

-So you will need an oscilloscopemeter to see its waveforms.
-Actually doubt that voltage multimeter will measure frequency into voltage rms changes, only a multimeter with builtin frequency meter can give a reading, so not reliable.

Footpedal to loopbanks mod is easy, solder a momentary footswitch leads parallel directly (hardwired) to a kp3 bank switch., better is to reroute it to an external connector like an usb connector, 4 pins to each SAMPLEA/B/C/D banks SW21/22/23/24 diode-side and usb shielding as the common switches-side SW_COM1 pin.
Here's a thread:
http://www.korgforums.com/forum/phpBB2/ ... 45f7841f75

[wax]

alright - i guess i found the mistake... there been no voltage changes while touching the pad at different positions but by moving the screen itself i found out that it got to be a broken wire - visually it's fine but i think this video prooves it...
http://youtu.be/BOpGy01uROA
you with me?

i had it working with a little tape - but after putting all the screws back in, it was dead again - might get squeezed too much?!

so i will buy a screen and be off my troubles hopefully- the cool thing is that by this accident i found out about the foot pedal mod - thanx for that - which brings up another 2 questions - if that's alright..

first off - these switches should do it, right?
http://www.musikding.de/1PST-momentary-footswitch



then it's great that Korg gave little solder points to every button - you suggested USB - but if I want foot control over 4 loops and maybe even HOLD and Sampling i need 12 pins - so i been thinking of VGA (15pin) - which gives me another button... i'm a bit unsure about the grounding you spoke about - i would connect each button with two wires going to a plug (vga) going to the switch..? i'm pretty much a beginner in such things
if you know a smaller connector then please inspire me
- cause i think there is not enough space inside for a VGA socket..


just to make sure the mod is worth it - there is no midi command for starting a recording (hitting A,B,C or D) while sampling is activated - i only could mute/unmute my loops via midi right?? couldn't find a midi implementation of the KP3 ..

learning so much about this unit these days - wonder what this OS 2.0 is all about

that touchpad explanation was a good read!

[bradkorg]

1) Yes, touchpad foilcable damage. Some copper trace in the foil flatcable is broken, mostly in the wider cable-panelside fold/bend sharp edge it breaks/cracks. good video.
(last try revive is to tape the fold that it doesn't move when there is contact, so tape it while it is in the working position)

2) 1PST-momentary-footswitch is correct, it means when pushed the switch makes contact ON only, not pushed stays off. These has the FASTEST reaction is better control.
You can built/drill a footbase like this etc.:
http://www.thomann.de/gb/line6_fbv_shor ... 488d442950

Any simple but SLOW reaction (tattoo/sustain pushed=ON) mechanical footpedals will work / google multi foot pedal etc., examples:
http://www.ebay.de/sch/i.html?_from=R40 ... ce0&_rdc=1

3) See servicemanual page 6 (Circuit diagram - Panel): the buttons HOLD/PAD MOTION/MUTE/SAMPLING/SAMPLE A/B/C/D shared 1 same connection side SW_COM1.
So for 6 buttons you'll need 7 pins/wires. Depends what you have in house, 2x USB male and female connectors can be used and the USB shielding/ground=the front bare metal casing, can be used as the 5th COMMON wire etc

Don't know if you are going to drill a hole in the KP3 casing/bottom plate for the cable/connector output.
Simplest is to use multi-flatcable-wires like the IDE flatcable, re-route to bottomplate bend the sidegap, tape the wires to prevent damage caused by metalplate.

4) This direct wired buttons mod has nothing to do with MIDI, it's just an buttons duplicated extension / wired remote foot pedals of the same buttons on KP3.

The guy using the FCB1010 footswitches (FAST switches) is a MIDI controller which is useless for KP3 because this MIDI cont. CAN'T send more than 1 button presses output MIDI note/message to control KP3 at the same time.
Thats why he did the direct wired mod., read the thread carefully.

-Hope this clears all.

[wax]

alright - finally i got all the parts i need - before replacing the screen i want to do the footpedal mod... so i don't mess around with the ribbon of the new screen..

i did find the same connection spot "SW_COM1" in the circuit diagram - thanx for the heads up - but I just can't find it on the board itself..
as far as i understand it's one of the many connection of the flat ribbon cable that connects both boards...?
those aren't labled and very small.. so i might just do it like the guy with the fcb1010 and wire up each button with two connections... those solder points are fairly big enough... would be cool to save a few pins on the output but i'm clueless about "SW_COM1"

for all you guys with a broken screen wire - i just peeled off the wire from the screen and badabim there you got 4 solid solder points - so it's worth a try to hard solder them to the connector pins 1-4 i guess...

[bradkorg]

Just use the multimeter Ohm measurement to check between those buttons solderpoints for 0.x Ohms is same common side.

Tape the new touchpad foilcable to prevent future crack due the bended pressure on it.

[Chimera11]

It happened to me too until it went completely dead, you can view the solution here: http://www.korgforums.com/forum/phpBB2/ ... 615#438615

[wax]

thanx for all the support - I finally had the time to replace the screen and do the foot pedal mod.... I took a RJ45 connector so that I now got access to A,B,C,D, HOLD and MUTE - also soldered a wire to SAMPLING....
So 7 wires for the buttons and one for the shared GND - couldn't be easier.
Been pushing this project for months but it took me less then 2hours to work on the kaoss pad - the pedal board wasn't too complicated neither

I had to be patient with the pedals itself though but it was worth it - ordered them via ebay from singapore for 1€ a piece incl. shipping (?!).... so the whole project was around 10€.. I'm super happy I went here as my screen died.

thanx again to bradkorg...