Yamaha DX7 Mk1 Cart Write Issues

Synth Repair
1

Hi, I’m new to synths and I’m having some trouble with my DX7 Mk1- it works and sounds fine, but I need help troubleshooting a problem with a RAM cartridge.

I bought this particular keyboard about eight months ago on FB marketplace; it had been imported from Japan (so it’s 100V for what that’s worth) and the seller had told me that the RAM was corrupted among other things but didn’t provide me with any more details than that. I took it home and reloaded factory patches from my computer and it’s been fine ever since. Battery voltage reads 2.8V so I don’t believe that will be a problem any time soon.

Flash forward to about a month ago and I decided to order a RAM cartridge from a vintage synth retailer just to have a larger library of voices without relying on having my computer nearby. It’s an MAARTISTS M128-X 128 voice cartridge (I really just liked the way it looked, what can I say) but when I finally got my hands on it, my keyboard can’t reformat it- I just get a “WRITE ERROR.” Since I don’t know anyone else with a DX7 (or anything in the same family) I haven’t been able to fully test the cartridge. I already tried cleaning the contacts on the cartridge board and the synth with some rubbing alcohol on a cotton swab to no success.

Are there any good ways to troubleshoot this issue without testing the cartridge on another keyboard? I’ve got a multimeter and some basic soldering experience so I’m not afraid to dig into the guts of either the cartridge or the synth to root out the cause.

Thank you for any help!

2

At 2.8V the coin cell on the motherboard will need changing.

Second the power supply will need investigating for electrolytic cap replacement. All caps in a DX7 are time expired.

Third, if you are using a 100V unit on a 120V power system - the power supply is being overcooked unless you are using it with an external transformer.

or

If the power supply has not been converted, take it to a tech who can do that.

If there is already a data card fault that happened from its time in Japan, that requires the bus and virtually every logic chip in the synth to be examined and fault tested. Mos tech’s will admit defeat when it comes to a bus/ logic failure as it takes too much time to be an economical repair.

If you want to try get a logic probe and a schematic and look for missing logic you can try it, BUT you will never understand how the bus works, you can only look for missing logic operations, or what should be there and isn’t to diagnose faulty parts.

and no, spare motherboards are not available.