RIGAS has expertise with this multi-loop controller. It has been used in various applications; the one it was designed for is boiler control. The application that we used it on (and serviced it on) was CEMS (continuous emissions monitoring).
On the CEMS application, the controller handled analog rescaling (for daily automatic re-calibration offsets), solenoid valve control, and some limited threshold/alarm logic.
RIGAS rewrote Rosemount’s original program to be friendlier when it came to entering cal gas values. It is called the “Plus 10″ program; essentially, the original program was moved up 10 rungs on the ladder and 10 lines of code were inserted just to handle calibration gas constants (and ‘yes,’ we had to put GoTo links in place of the old constants cells).
We have some parts (very limited though) and know where a few old GPC1500s are. We would buy them from our customer, refurbish the units, and resell them to you with a warranty.
If you’re looking for a quick fix – try replacing the battery. That could cure a whole host of problems.