Gk3 pickup. 1st,2nd,3rd and fourth string not working. Checked wires, cable sprayed contact cleaner on all parts and still dosen't work. It's a new sensor I ordered.

you have a bad pick up as you have six or more depending the the guitar ,so check out the guitar forst,.

A Gk3 cannot be connected directly to an electric piano or synthesiser. The 23 pin DIN connector connects the GK3 / GUITAR to a Roland guitar synthesiser which produces the synth tones . This unit can be connected via midi cable to any external keyboard or synthesiser...to produce different or varied tones from the external synth ........provided the devices are able to communicate with each other...see the midi implementation charts for each device for information....

You must connect a short jack cable between the GK2 or GK3 and you normal guitar jack out. Secondly, the switch on the GK should be in the middle, that will give synth & dry guitar simultaneously.

spray the controll with cleaner. if it dosen't work replace the controll

Stop by Guitar Center and they carry spray product(s) made for cleaning "pots" IE: Blue magic, etc...

It seems that your 3-way switch is suffering from bad contact. Well, there are three things you can do:

1 - Take the guitar to a service representative and have it repaired,
2 - If you are proficient in the use of a soldering iron, you could desolder it from your guitar and replace it for a brand new one (do not forget to take notes of the cable colors and where they are soldered before removing it), and
3 - Try using a contact cleaner spray to clean its contacts.

The contact cleaner spray is a spray can filled with special formulated chemicals and/or gases that helps cleaning the switch and pot contacts. It generally comes with a thin tube that allows you to insert its tip inside the switches or potentiometers and spray its contents exactly where it is needed. While spraying, move the switch rocker or potentiometer cursor from one side to the other, allowing the fluid to clean the contacts, removing any debris that might be located there and originating the bad contacts that may be causing the scratchy noise you hear..

These contact cleaner sprays can be found in most hardware stores, electronics dealers, and hobby shops or even in the Internet, from different brands (3M, Polywater, MGC chemicals, CRC, etc ).

Hope this may help you put your Epiphone to scream loud and clear again...

I would suspect a setup problem. Your best bet would be to contact Rolan Customer Service. /here's their link-
Roland Support

In a guitar with 3 pickups a 5 way switch works like this. With the switch all the way forward( towards the tuning pegs) the pickup closest to the tuning pegs or end of the neck is completely on ( if your volume control is all the way on). The next position (moving away from the tuning pegs or neck) is a combination of the neck pickup and the middle pickup. The third position moving away from the neck is completely the middle pickup. The fourth position is a combination of the middle pickup and the bridge ( where the strings are fastened) and the fifth position is completely the bridge.

Have you tried another cable between amp and guitar? Usually the cable goes bad first. Have you tried another amp or possibly tried another guitar on your rig? If this still indicates that your guitar's Standard 1/4" TS Jack is noisy, remove the oval cover over the jack and check the solder joints for the wiring. Follow the wires back to the tone and volume pots and check those solder joints. If everything is secure...Plug in, power up and check for noise while turning the volume pots stop to stop. If the pots make a scratching noise, shut down rig and unplug the guitar. Get a can of spray contact cleaner with a small extension tube (available at electronic shops) to spray in the pots while turning them. (May have to remove pots fom the guitar to get at small openings on side of pot can.) Spray jack and test for noise. Jack STILL
noisy...If you can solder...unwire old jack, remove from guitar, take to electronic shop, match to Standard 1/4" TS Jack, install in guitar, resolder wire connections and test. If you cannot solder...take guitar to
a reputable shop or dealer that does this repair. Good Luck! P.S. The
spray contact cleaner can be used on the amp jack, pots and switches
too...just make sure the amp is unplugged from the power supply before
doing any spraying.

I have the same problem. Only the 1st, 3rd and 5th strings respond. This is not a sensitivity adjustment. The unit does not see the strings. I called Roland and was able to purchase just the pickup itself rather that the entire GK-3. The pickup was about $35 but took 4 weeks to arrive. When it finally got here I was excited. It was not difficult to remove the old and replace it with the new. I plugged it in. NOTHING CHANGED! I believe and hope it ti the 13-pin cable. I have read where these cables are just poorly made and many users have spent a considerable sum on the cable, most recommending having one in reserve always as they are sure to go out.