Vintage Synth Repair

Hi folks,

My old trusty DX7-II FD, with the E! add-on board, has been entombed in my basement (shame on me) for a good several years. I've recently brought it out a couple of times and powered it up, but am having some issues.

I get no sound, either from the A/B outputs nor from the headphones jack. As far as I can tell, most of the buttons seem to work when in edit mode, but in play mode, the only non-functioning aspect that I can tell is that I am unable to select voices (1-32 or 33-64) using the main rows of buttons. The single/dual/split buttons seem to work as I recall, and the A/B button will switch between the 1st and 33rd patch, but I can't select any other sounds using the numeric buttons.

Amazingly, I am still able to load a soundbank off of a twenty-plus-year-old floppy, so I guess the disk is operational too.

Since all of these buttons appear to work fine in edit mode, I figure there is some software/firmware glitch going on somewhere. I am returning to this since the last round of trying it a couple of months ago (part of the reason it's sat in the basement is my being very busy in this part of my life with other responsibilities!) I recall doing some web searches at the time and finding a PDF of the service manual somewhere. However, I don't recall seeing any "reset" instructions.

Anyone got any ideas?

Much appreciated in advance,
Chuck