> People have had the same problem with connecting the PS/2 I-PAC or J-PAC with an
> adapter. At least for the Ultimarc products, they actually sell a custom USB cable
> that works because their older encoders auto-detect PS/2 or USB. I'm not sure about
> the Hanaho Hotrod. Is Hanaho still in business?
I think Hanaho went defunct back in '07 or '08. IIRC they had some legal trouble with Capcom just before disappearing.
I don't recall ever hearing of a fully workable PS/2-USB adapter for a HotRod from back when I owned one. We used to have a HotRod support site here on MW back in the day and it was a really common question. RB's suggestion of a modern encoder sounds like it makes the most sense.