I have for sale a Panasonic FS-A1FX with a 256kB RAM upgrade. The disk drive has received a new belt and a capacitor replacement. The machine has no OPLL FM chip but this also means there is no noise from that chip (and an external FM is much less noisy), of course the OPLL can be added to the board with the ROM (sacrificing the onboard firmware). The price is €300.
If you are interested please send me an e-mail. The address is on my profile page.
