Are you in Poland? I'm taking one of my Keithley 197s apart for parts and I can send you my 1972 GPIB board for little. There are many dying electrolytic capacitors in it so I consider it is beyond economical repair, and I already steal it's CPU to recover an K617.
Just to cover the shipment from Switzerland (likely 9 euros) and maybe additional 10 euro to cover the bother to pack it up and for the trip to the post office.
Nevermind, just realized that you managed to fix it. Hope it can be a permanent solution.