For the past few years My Ensoniq VFX-SD has been giving me the Keyboard Calibration Error prompt with increasing regularity. I found that if I left it on for a while and let it warm up I could restart it and it would calibrate and start up. That strategy no longer works, and now it will not pass the Keyboard Calibration Error prompt. The keybed was replaced decades ago. Even so, I checked the cable between the two boards and resoldered the joints (even though they looked good). I’ve tested all the voltages on the power supply boards as per the service manual and all are within spec. The battery has been replaced in September of 2010 and its current voltage reads 2.9VDC. I’ve cleaned all of the ribbon cable connections with Caig Deoxit D5. The inside of the unit and all of the circuit boards are visually pristine and there are no obvious bad appearing components. Any suggestions as what my next step would be?