Kawai K3 Dead, No Display, No Sound

Synth Repair
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1

Kawai K3 – Dead

I have a K3 on the bench and the power supply all checks out. 5V, 12V and -12V all in spec. I have checked the supply voltages on all the PCB’s and the same levels as at the power supply is measured. So the power system is working properly. I checked the RESET line on the 8051 CPU chip and it is being reset on power up. The 3V Lithium battery was dead so I replaced it. So far nothing has changed and the display is dead even though the synth is powered up. I checked the Clock Crystal and 14Hmhz and no issues. I tried the 3 lowest white key press on power on , still nothing. I am quickly running out of options.

Anyone seen this before?

2

If you have an oscilloscope I’d be checking the MPC clock is running, then the RD//WR and PSEN lines as they should be strobing whenever the MPU tries to access anything external. I’m not an expert but did resurrect a brain dead Roland Jx-3p with the same symptoms. Good luck with the repair.

3

There needs to be a reset procedure when you change the 3V battery.

Did you do that?