ESQ1 Keyboard multiplexer

Hi Everybody,
I’m French sound engineer new on this forum working on a US ESQ1 plastic model which has been plugged directly on 220 Volts…All the fuses were burned and a lot of power supply capacitors looking like cakes going out of the oven…
Now, I’ve been fully recap the power supply, change the ROMs with newer 3.5, the synth boots normally, the display and all the front panel switches works fine but since I touch on any keys on the keyboard it turns every times on soft ERROR 01.
Does anyone knows how I can test the IC 138065002B keyboard controller ?
If it doesn’t work is there an equivalent to this ship since the original is out of stock ? Does this multiplexer datasheets exists ?
Thanks to all for your help.

You can test the keyboard controller with a logic probe or oscilloscope. The keyboard ports on the chip
should be pulsing high and low as it’s scanning the keyboard. The data from the chip is then sent to the DUART chip. (U6 - 2681). The keyboard controller chip is a Rockwell R6500 cpu similar to the 6502 as used in older computers. It was a factory programmed chip and is probably obsolete. If you need a replacement you will probably have to salvage another ESQ1 or SQ1. A gentleman ( Rainer Buchty ) was working on reverse engineering the keyboard chip but the link on his website no longer works ( I’m also looking for a keyboard controller chip for an SQ1 plus. Both Syntaur and Buchty currently have none is stock.

Thanks for your answer Pat, I’ll follow your advice and will turn on my Schlumberger this weekend to check the 6500 input/output.
But I’m sure it exists a solution to switch this old keyboard chip with a new IC, there’s no thousand way to encode a keyboard instead Ensoniq synth system.