Kord Prophecy - parts/service help needed!

nico88 · Post by **nico88** » Sat Jul 07, 2018 7:11 am

I am currently trying to repair my Korg Prophecy. Does anyone know what the part number or specification is of the MOSFET transistor that it is attached to the heatsink of the ACDC SMPS power supply?

The original problem was the sound output stopped working, and a couple of people have tried to fix the Prophecy and in doing so the SMPS Mosfet transistor has been removed/lost!

All help would be very much appreciated!

Regards,
Nic.

voip · Post by **voip** » Sat Jul 07, 2018 4:50 pm

It might be worth temporarily wiring up external 5V and 12V supplies in place of the KLM-1856 board outputs to see if the rest of the synth works.

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nico88 · Post by **nico88** » Sat Jul 07, 2018 5:37 pm

voip wrote:It might be worth temporarily wiring up external 5V and 12V supplies in place of the KLM-1856 board outputs to see if the rest of the synth works.

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Thanks VOIP, it had power when we first tried to repair it, just no sound being produced from any output. The latest attempt to repair is probably our most hopeful, we work in Semiconductor electronics, so replacing the mosfet should be easy provided we choose the right spec.

voip · Post by **voip** » Sat Jul 07, 2018 6:25 pm

The PSU schematic is missing from the service manual, for some reason. It looks like it's a simple flyback type, as is common in quite a few Korg PSUs. FETs such as 2SK1643, 2SK1501, and 2SK2481 feature in other Korg flyback SMPSU designs of the Prophecy era, and would probably work here, too. Just verify that it's the correct type (N or P channel) for the connections and polarity on the PCB. Also, ensure it's an encapsulated type.

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nico88 · Post by **nico88** » Sat Jul 07, 2018 6:36 pm

Thanks VOIP for your superb response. Very much appreciated.
I will let you know how we get on!
Thanks once again, and have a great weekend.