SP250 with damaged amp board

[Alan3666]

Hi, can anyone please help?

I bought a Korg SP250 on Ebay sold as no power parts only.

It was in great condition, used as a church piano, looks like new.

I opened it up and was surprised to find the amp board was badly damaged. I think someone has yanked the keyboard off its stand while the audio cables were still plugged in. The printed circuit board is split and cracked all around the jack sockets.

I contacted Korg but they simply responded saying part was obsolete.

Can anyone suggest a supplier, or has anyone a spare even if its damaged.

I'm pretty sure the components on this one should be good.

Any help or advice appreciated.

Alan

[voip]

Ouch! The bad news, as you've already found out, is that replacement boards aren't available from Korg or Korg parts stockists, although it might be worth searching eBay from time to time for spares. An entire SP250 was recently sold for less than the list price of a replacement board. The good news is that the board appears to be a single layer printed circuit board, so it might be possible to piece it together again, although it will be a labour of love!! If any components have been damaged, try to get replacements. Try and piece together the broken bits of PCB and carefully superglue them together, applying glue from the topside only. Leave for at least 24h to allow the glue time to harden properly. Rejoin the broken tracks with solder, using wire to bridge larger gaps. Replace broken components, and hope for the best.

.

[Alan3666]

Ouch! The bad news, as you've already found out, is that replacement boards aren't available from Korg or Korg parts stockists, although it might be worth searching eBay from time to time for spares. An entire SP250 was recently sold for less than the list price of a replacement board. The good news is that the board appears to be a single layer printed circuit board, so it might be possible to piece it together again, although it will be a labour of love!! If any components have been damaged, try to get replacements. Try and piece together the broken bits of PCB and carefully superglue them together, applying glue from the topside only. Leave for at least 24h to allow the glue time to harden properly. Rejoin the broken tracks with solder, using wire to bridge larger gaps. Replace broken components, and hope for the best.

.

Thanks for the encouragement. I may have to resort to rebuilding but I'll park that for now.

Its a real shame. The keyboard looks mint. I have a Roland stage piano which I think sounds great but it looks very plain. Whereas the Korg looks like a piece of art. I owned an MS2000 for a while (why oh why did I sell that?) and it also looked good, with real wooden cheeks.

Anyway, I'll get there. I bought this for my son. He's a doctor working in Edinburgh and during these strange days he's keeping pretty busy, so I've got some time to get it going.

Al

[Alan3666]

So I managed to get hold of a replacement Amp Board but the vendor advised that it was only producing sound on one speaker. I installed it and sure enough only right hand side speaker is working. However both Audio Out channels are working and left and right headphones are good. Looking at the schematic in the service manual I reckon the fault on this card most likely to be the power amp chip but it looks like someone has already replaced this judging by the solder. I'm waiting on a scope arriving then I'll be able to trace some signals along both channels and see if I can id fault.

If its not the power amp then it could be the equalizer chip that sits before the amp. I hope its not that. I dont fancy de-soldering all those pins.[/img]

[voip]

Sounds promising. Good luck.

.

[Alan3666]

So when the scope arrived I found good signals on audo left and right and same on the headphone paths.
On the speaker paths I could trace the right audio from R74 through the EQ chip into the amp chip and out to the connector CN6, but the left speaker signal stopped at R75.
I have now removed the amp chip. I can now read a good signal at both R8 and R9 when I play a note on the keyboard. R8 and R9 are the resistors that feed left and right signal from the the EQ chip into the left and right input to the amp chip.
I've ordered a replacement chip.

I've also sourced another Amp Board as a backup.

Alan

[Alan3666]

Last update

Chip replaced all working.

Now have a good spare amp board



Alan

[voip]

Great to hear it's now working :-)

.