Korg Poly800/EX800 Users

You definitely a problem with the keyboard multiplexing circuit. Check out the schematics in the files section under "Poly-800" -> "Servicing"  section
You will see a zip file in there P800Schematic.zip Pages 2 and pages 5 show the switch matrix design.
I can see that 8-3AB are the row connected to the Step button and the "8" keypad. That row also corresponds with bottom C on your keyboard.
There are two distinct possibilities. One is that the signal wire for that row is broken somewhere. Two, the chip itself (IC33) which is a 40HC240.

I've seen those chips wind up with a dead input before. Probably because there's no debounce caps on the inputs to reduce static.
So I would probably replace that chip. But I would also have a darn good look at the keyboard connector cable pins and socket and check for corrosion, broken/bent pins etc.
As for the AtomaHawk, you need to install the HAWK kit first. And the HAWK installation is not an easy one. Spo email me directly to chat about that.
/Mike

      From: "robertburnham23@... [korgpolyex]" <korgpolyex@yahoogroups.com>
 To: korgpolyex@yahoogroups.com 
 Sent: Wednesday, February 25, 2015 1:52 PM
 Subject: [korgpolyex] Poly800 button issue and Atomahawk question
   
    Hello people
I have recently purchased a Korg Poly800 from eBay but it has a few issues unfortunately. The main one that is troubling me is the 8 button does not work. I opened the unit up and checked if it was a contact issue, but it is the actual button on the board that does not work. Has anyone had a similar issue before? There is another issue with the keys, every 8th key does not sound. I believe this is down to the IC33 chip, is there any way the two faults could be related?
Also I am interested in the Atomahawk upgrade to give me full MIDI control over the unit. However my soldering skills are pretty non existent. Is there any way of getting a pre-soldered version?
Any advice would be greatly appreciated

CheersRob  #yiv7636789417 #yiv7636789417 -- #yiv7636789417ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv7636789417 #yiv7636789417ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv7636789417 #yiv7636789417ygrp-mkp #yiv7636789417hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv7636789417 #yiv7636789417ygrp-mkp #yiv7636789417ads {margin-bottom:10px;}#yiv7636789417 #yiv7636789417ygrp-mkp .yiv7636789417ad {padding:0 0;}#yiv7636789417 #yiv7636789417ygrp-mkp .yiv7636789417ad p {margin:0;}#yiv7636789417 #yiv7636789417ygrp-mkp .yiv7636789417ad a {color:#0000ff;text-decoration:none;}#yiv7636789417 #yiv7636789417ygrp-sponsor #yiv7636789417ygrp-lc {font-family:Arial;}#yiv7636789417 #yiv7636789417ygrp-sponsor #yiv7636789417ygrp-lc #yiv7636789417hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv7636789417 #yiv7636789417ygrp-sponsor #yiv7636789417ygrp-lc .yiv7636789417ad {margin-bottom:10px;padding:0 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