sp 250 fault


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Hi All,
Just came across this forum website today. I am not a keyboard player but am an electronic service technician for over 30 years now. A friend has asked me to try and sort out a fault on his Korg sp 250 keyboard. The symptoms are the following. When powered up the unit will activate the metronome or some other effects features without anything being touched. Sometimes the unit will appear to operate normally but when some base notes are pressed the metronome will activate. Some of the other effects led's will begin to flash. I disconnected the connection from the user button panel to the cpu board but the problem persists. The only checks I carried out so far was to check the 12, 9, 5 and 3.3V supplies. Am I looking at a new cpu board and if so can anyone suggest where I might purchase one.
Thanks in advance from the 'old timer'.
 
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happyrat1

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First of all, I'd suggest doing a system reset on the keyboard before any screwdriver work.

It sounds to me like the metronome has been programmed by a previous user to activate on a bass note.

Secondly for Kurzweil Parts I have these listings.

Specific parts for something that old can be hit or miss though.

http://www.instrumentalparts.com/kurzweil-parts.html

https://syntaur.com/kurzweil_pc.html

http://www.fullcompass.com/brand/KUR.html?page=1&query=&categoryOrder=Bestselling&view=&ipp=24

If those sources fail, then look around on ebay for junkers for parts.

Gary ;)
 
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Thanks happyrat1 for getting back to me. What is the procedure for defaulting this unit.
It's worth mentioning that even if no keys are pressed the metronome will activate and some of the led's such as piano1, piano2, organ will start flashing after 5 seconds from switch on.
 
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Gary
Am I missing something?

The Op is asking about a Korg sp 250 and you are quoting Kurzwell!
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It sounds like the owner has pressed and held a combination of buttons or keys to get it operatings as it is.

The keyboard should nirmally return to default setting in powering down so something is a miss.

Try resetting the Metronome by pressing and holding the Metronome button, then press the B5 and C6 keys together.

The detailed Manual should also provide info on how to do a system restore which may also help.

You could always give Korg tech a ring in the Country where you live.

On my Korg to do a system reset I have to press and hold a specific button then power the keyboard on.

The 250 is an older model as the Korg sp 280 is the current one.
 
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happyrat1

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Sorry man, you're right. I zoned out. I Saw the SP and assumed Kurzweil. Too many similar model numbers :(

Anyway he should be able to google find the manual online and do a system reset according to their procedure.

As for the parts vendors? They also carry Korg Parts.

Gary ;)
 
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Thanks guys,
Got the manual and tried a reset but alas, no joy. The buttons seem to have a mind of their own. Effects will come on of their own accord without anything being pressed on the unit. Something on the cpu board I suspect. These days I don't carry out much board repairs since almost all components are smd's. Eyesight is also another factor. If anyone comes across a board for sale somewhere please post here. Thanks again.
 
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Sorry that the problem is still there.

A quick look online and zero circuit boards available, they used to cost $75.

A look on eBay has a Korg sp 250 available for spares or repair at $200?

Those that are working are $400-500.

A new Korg sp 280 is $700.

Maybe it is near time for your friend to look for a new keyboard, there is plenty of choice for them. Offsetting the cost of a new keyboard by selling the old one on eBay?
 
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Thanks biggles,
I agree with you about retiring the keyboard . However guys like me find it hard to 'write off' gear having come through the service industry for over 30 years where everything was serviceable at a reasonable cost and all discrete components were available. The workshop manuals and schematic diagrams were fantastic and contained circuit descriptions etc, etc. Back then a 10 year old piece of equipment was considered new. Apologies for my reminiscing.
 
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I know what you mean.

I have been building PCs for 25 years and at no time has a motherboard been repaired and very few have been replaced whilst retaining existing CPU and RAM.
 
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I must be unique. I repaired a dell mother board about 1 month ago that I was using as a Linux server. Out of desperation and in a corner one Sunday afternoon I replaced about 4 caps and one regulator which brought the system back to life. I often wonder about the 1000's of PC's that have gone to their grave's when a component costing a few cent and a little time would have repaired it. Such is progress.
 

happyrat1

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Sometimes board repairs are as simple as eyeballing a flaky solder joint and reheating it.

Other times you have to break out the scope and start tracing logic pulses all over the place.

In this case I'd still be inclined to suspect some sort of firmware/software problem or something simple like a sticky switch somewhere on the panel.

Fortunately there's a full service manual with schematics available on the web.

https://elektrotanya.com/korg_sp-250.pdf/download.html

I'd suggest downloading it and digging in.

Gary ;)
 
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Hi happyrat1,
I might get stuck in some day soon. I suspect this could be a sw problem ok. If this is the case checking with my scope could lead be around the block for days. Keep you posted.
 
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happyrat1

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Another thing to check for is power supply issues. A few transient spikes on the supply rail can ruin your entire week. :)

Gary ;)
 

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