Hello Mr. Ohle,
in the past we worked on a case where an other customer had problems similar related to yours where our older GPIB boards work with older Stanford Research Systems instruments, but our newer GPIB boards failed; at least not without some modification in the connection between the board and the instrument.
The workaround was to place a 270 pF capacitor between pin 10 (ground) and pin 17 (DAC) of the instrument's GPIB connector/cable.
Maybe that will help in your case too, but please keep in mind that NI is not reliable of damages which may occur at your device, GPIB board or computer based on making this kind of modification.
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Kind Regards,
Heiner Illig
NI Germany