I do wish people would put a link to all the threads they post on each Amiga board

Brilliant, thanks for the info Anthony: I dug out the schematics and posted the following on amibay:
Pin 25 is connected via a diode (d800) to +5v - that could have gone.
Pins 8, 10, 11, 12, 21,22 and 23 are connectedt through pull up resistors in RP802 (220 or 330 ohm) to +5v
Each pin on the connector is connected through a ferrite bead (EMI1800-1817)
The schematics say the diode is a 1N914, for what it's worth...