Ensoniq SQ80 Cartridge Bug

I recently purchased a 16-in-1 rewritable cartridge for my Ensoniq SQ80 from EBay. When the cartridge is inserted pre-startup, the keyboard won’t power on. If I insert the cartridge post-startup, the control buttons of the SQ80 stop working completely and I’m unable to load any banks from the cartridge. If I then remove the cartridge, the keyboard returns to the “Calibrating—Do Not Touch Keys” display and freezes. Does anyone have any experience with a similar issue? The seller has offered to replace the cartridge, but I’m worried the cartridge drive might be the culprit. Unfortunately I have no other working cartridges to test the drive with.

Finding someone nearby who has an SQ-80 or an ESQ-1 might be the simplest thing - see if their keyboard crashes when the cartridge is installed. My guess is it is a cartridge problem rather than an SQ-80 problem. The cartridge interface is pretty simple - just a card slot basically - so there’s not much to go wrong there.

Did the seller have a keyboard to test the cartridge on before selling?

That is encouraging to hear. The seller didn’t mention that the cartridge had been tested, but did mention that a very few cartridges had been returned as defective and replaced with working ones. I’m returning the cartridge for another, so hopefully that’ll take care of it.