Keyboard malfunction riddle - can't work this one out, I'm totally at a loss!

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Hello, I've joined this forum because I've asked everyone I can find and can't get an answer. I'm hoping someone here has an idea otherwise I don't know what to do. My question is: why would a Korg SP100 with the same equipment work perfectly in one location and not at all in another?

I bought a second-hand Korg SP100 which I saw worked fine. I take keyboard home and with headphones in turn it on. The lights go on, there is a buzzing sound in the headphones with quickly settles to a low hum. I start to play and within a few seconds the sound cuts out. Lights stay on.

I take the keyboard for repair (the person I bought it from paid). The guy at the shop says that when he uses the keyboard, the whole thing switches off after a few seconds. He puts this down to a fault with the adapter connection and fixes a couple of bent pins in the connecting socket. The keyboard works flawlessly at the shop with my same adapter and he plays on it for two hours before having me collect it.

I take the keyboard home and plug it in. But the problem is exactly the same! I try it in all the different sockets and with each plug in the two extensions we have. It's the same problem however I try it.

I call him, I take it back to the shop. I take my headphones and my adapter and plug it in to show him that he has not fixed it. But the keyboard works fine - no buzz, no hum, no cutting out. I play it loud, soft, I play loads of notes and I am forced to admit that yes, it does work.

So I take it home and plug it, using an extension with a surge protector without other appliances attached as the guy at the shop had. It works perfectly! Then it cuts out! Then it works again. This morning it worked for a while. But sometimes when I turn it on, I can get no sound whatsoever, not even a buzzing. Sometimes it will cut out when I play more than a few notes at once (say, eight notes at once on what is supposedly a 32 polyphony keyboard) or when I play loudly but sometimes it will just cut out if I'm playing one note quietly.

It's so frustrating when I can see the keyboard work perfectly front right in front of me in one location and then not be able to use it when I get it home. Obviously the music repair shops I call don't know what the problem is and tell me to bring the keyboard in. The only thing is, they won't know whether they've fixed it until I've paid them and got it home which is no good to me! I can't sell it to someone else in good conscience.

The only other thing I can think of is that the adapter is a mismatch for the keyboard - it's 9v but needs to be 12v. But this doesn't explain why the keyboard works with a 9v adapter in one location and doesn't work with the same adapter in another. I'm waiting for a new 12v adapter to arrive but if that doesn't work I'm screwed unless I can get the person I bought it from to take it back. I'd rather fix it as it's a long way to travel back.
 

happyrat1

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First off, the adapter should probably be a REGULATED 12V adapter. Just because it's made in China and says 12V on it doesn't necessarily mean it won't cook your circuits. You should definitely order an original Korg part for it.

Secondly the common factor in your experiences with the repair shop is motion. Everytime you moved the keyboard it either worked or it didn't which leads me to suggest a loose connection inside, probably in the audio output circuitry but not necessarily limited to that circuit.

If you are strong of heart and know what to look for open it up and look around for loose solder joints or cold solder joints and unplug and replug all the internal connectors.

With this kind of intermittent it's often a cold solder joint on the motherboard or a marginal solder connection to an internal wire or cable.

It can also be the most difficult kind of failure to troubleshoot because of its intermittent nature.

Anyway if the tech who sent it back to you guarantees his work send it back to him until it's fixed PROPERLY or else try and get your money back and take it to someone who actually knows his job.

Gary
 

happyrat1

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BTW, just to eliminate the obvious, try a different pair of headphones and try hooking it up to an amp in case it's crappy headphones causing the problem. ;)

Gary
 
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Thanks for your reply Gary.

I've tried all sorts of new cables and a couple of different headphones so they're all OK.

I think I'm a bit out of my depth as far as opening it up so that'll probably involve a few more repair bills - no guarantees form the tech guy and I don't think he really knows what's wrong with it beyond the pin being bent in the adapter socket. I can hear something tiny rattling when I move the keyboard - but it also rattled when the keyboard was working perfectly so I dismissed it as the cause of the problem. Could a loose solder joint also mean that the keyboard doesn't pick up a plug-in damper pedal signal? The damper was working but has stopped since I last moved it or since the repair guy opened it up.

As for the adapter itself, I actually tried to find one for my model but was unsuccessful. The online seller I got this one from has a lot of good reviews from people using electronic instruments so that was the best I could do. I will move it to a neighbour's tomorrow and see whether it plays properly there. If it doesn't then there must definitely be a problem with the keyboard and I'll know I need to start looking for a decent repairman.

Thanks again,
Michael
 

happyrat1

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For the adapter try contacting Korg USA directly. They should still have the part in stock. The SP100 is not THAT old.

http://www.korg.com/us/support/contact/

As for the rattling! DANGER WILL ROBINSON DANGER!!!!!

If there's a loose screw or a bead of solder rattling around inside the case you are playing Russian Roulette everytime you plug it in or power it up!!!!

At the very least remove the bottom access panel and see if you can shake the bugger out!!!! It should be opened up and checked out before you plug it in again.
 

happyrat1

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If you're feeling brave, here's a youtube video of a Korg 01W Pro being torn down and reassembled.

All you'd really have to do is remove the bottom panel and shake out whatever piece of crud is floating around in there.

 

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