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KingKorg with malfunctioning C#, F, and A

 
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sinneb



Joined: 30 Oct 2015
Posts: 6

PostPosted: Fri Oct 30, 2015 7:42 pm    Post subject: KingKorg with malfunctioning C#, F, and A Reply with quote

Hi all,

A while ago I bought a secondhand Kingkorg. Loved it until it started malfunctioning. After a while, the keys C#, F, and A for each octave stop functioning. A few minutes before they stop functioning, said keys always exibit maximum velocity... When I first encountered this problem, it started occuring after 30 minutes. Now the problems are effective right after starting the KK. Restarting does not fix the problem, only after leaving the synth off for at least an hour.

Did all resets etc from the manual. Then I opened the KK and checked the keyboard scanner. I think the KK scans the keys in blocks of 8 addressed by 3 lines from the CPU. The blocks of 8 seems fine and my multimeter shows all connections in place. The 3 lines from the CPU are not accessible to me, at least that's not how far I want to disassemble the synth.

Does anyone have a clue? I might try other reset options or even firmware updates but I cannot locate any information on that.
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SanderXpander
Platinum Member


Joined: 29 Jul 2011
Posts: 7860

PostPosted: Fri Oct 30, 2015 10:16 pm    Post subject: Reply with quote

I think you've already gone further with diagnosing this yourself than almost anybody on here would. I would recommend taking it up with a service center at this point.
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Narioso
Senior Member


Joined: 15 Oct 2015
Posts: 300
Location: Sweden

PostPosted: Sat Oct 31, 2015 8:04 am    Post subject: Reply with quote

Have never looked inside Korgs, just Rolands and Kurzweil stuff.

Have fixed keys like on D50, where the rubber part pressed by key, also having a conductive rubber inside - just lifted these then cleaned with antioxidation spray on circuit board below keys.

No idea what fails on Korgs though. But I would look at these spots I mentioned, if previous owners dropped a can of CocaCola inside or something. One never knows.

If there are damage on outer chassis one could start looking for possible breakage of circuit boards. May be hard to find, but with cooler spray and a hair dryer back and forth it helps. Since your problem is systematically over the same keys in octaves this is more probable - since you checked cables. Look for cracks on edges of circuit boards.

Odd thing is that nowhere is it mentioned firmare revision/version or anything like that. Not presented on machine, I gather you need the service startup procedure somehow. If there are service manuals available that is - you will be able to run many tests built into unit that is used in production and service. Usually key/keys pressed while power up.

There got to be a firmware revision, and also ability to check what is latest. There is no such thing as bugfree software at first series in production.
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MIDI gear: Sequential REV2.16, Prologue-8, Hammond XK-3C, Kawai MP7SE piano, Nord Lead 2X, Roland D-05
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sinneb



Joined: 30 Oct 2015
Posts: 6

PostPosted: Sun Nov 01, 2015 8:52 am    Post subject: Reply with quote

@SanderXpander: guess you're right...

but

@Narioso: yeah, I was hoping for a service manual explaining the tests you're describing. Or indeed a firmware revision and current version indication.
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sinneb



Joined: 30 Oct 2015
Posts: 6

PostPosted: Sun Nov 01, 2015 8:55 am    Post subject: Reply with quote

and when I have the service manual available, I will check the integrity of the PCB's - without such a manual laying out the essential checks and perhaps even a schematic of some sort, work on the PCB's is almost impossible.
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Narioso
Senior Member


Joined: 15 Oct 2015
Posts: 300
Location: Sweden

PostPosted: Sun Nov 01, 2015 10:09 am    Post subject: Reply with quote

sinneb wrote:
and when I have the service manual available, I will check the integrity of the PCB's - without such a manual laying out the essential checks and perhaps even a schematic of some sort, work on the PCB's is almost impossible.


You could try and do visual inspection only - you don't really need SM. Maybe service manual helps in dismounting things, but you already did that it seems.

Look first at cards that have connector or switches etc - and around those areas. Those are the places more likely to been hit and cause damamge to interial. Look at edge of cards first, then maybe over surface if any suspected lines of breakage.

Headphone outlet, and outlets on the back, and big switches on front panel. If unit ever fell over to floor or something those place with a plug into etc a likely to break things inside.

Slightly pressing circuit boards while running may also give a hint to an area if keys work/fail while doing that. You already have a temperature effect as you described and it worked while cold. So warm up(maybe with help of hair dryer) until fail, and then cooler spray on areas to see if working. This kind of procedure.
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MIDI gear: Sequential REV2.16, Prologue-8, Hammond XK-3C, Kawai MP7SE piano, Nord Lead 2X, Roland D-05
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sinneb



Joined: 30 Oct 2015
Posts: 6

PostPosted: Wed Nov 04, 2015 10:46 am    Post subject: Reply with quote

thx for the very helpfull instructions Narioso. Will start work on the KK soon!
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sinneb



Joined: 30 Oct 2015
Posts: 6

PostPosted: Thu Dec 03, 2015 12:37 pm    Post subject: Reply with quote

To answer this thread: had the KK fixed by a professional technician. It happenend to be the connector inbetween the DSP board and the main board. This miniature connector was badly goldplated and had a number of bend pins. Could be due to bad assembly or a previous repair (!). Fixed now, KK back in business Smile
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sinneb



Joined: 30 Oct 2015
Posts: 6

PostPosted: Thu Dec 03, 2015 12:39 pm    Post subject: Reply with quote

just as Narioso expected Cool
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