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.
This particular analyzer is one of RIGAS’ favorites to work on (i.e., repair).
Here is a list of some of our checks that we perform before we release your analyzer for shipment:
- Noise on range X1 should be minimal (±1 count)
- All ranges should be correlated (especially those with an optional range trim board)
- Response to certified calibration gas should be equal to or better than factory specifications
- When TP5 = 5 VDC then [a] the display reads 100.00,  analog output is either 100mV or 1V or 5V (depending on jumper configuration,  isolated current output = 20 mADC
- Analyzer is clean
- Insulation is re-glued
- Frayed wires are fixed
- Plexiglas is grounded
- A/C power switch leads are coated with “liquid electrical tape” to prevent inadvertant electrical shock to the end user
- Ribbon cables are pristine
- Rear terminal strip has a sticker that shows what functions are on what terminals
- Zero pot (potentiometer) is greater than 50% (the higher the number here, the less contamination in the analyzer tubing)
- It needs to look good again (paint job if necessary)
- Flame safety circuits MUST work properly
- Backpressure regulator works as designed (and controls at a very reliable value)
- There’s a bunch more, but we don’t want to bore you with the entire list!
Give us a try by calling us at 877-616-0600.
Description: This is an isolated signal analog output card used industry wide. The analyzer’s potentiometric output (DC volts) signal drives the signal for the 4-20 mADC card (usually 0VDC input = 4 mADC output & 5 VDC input = 20 mADC output). The term “isolated” refers to the fact that the output signal is not referenced to earth ground and is therefore much less susceptible to interference from other voltage sources. Milliamp signals are very useful when running long signal loops (on the order of tens of feet to thousands of feet long; note that total loop resistance has to be less than 850 ohms).
Where used: 400A,755,755A,755R,870
Static sensitive: This board is not very susceptible to ESD but handle it with some ESD protocols.
Replaces: Rosemount 620433 (in kit p/n: 621023)
Compatibility: RIGAS has released its compatible version of the OEM board. Some nice enhancements were included:  hook-type test points,  better labeling,  heat sinks,  zero & span potentiometers can dual configuration (i.e., adjustable from the top or from the front).
Please specify potentiometer type when ordering. Choices:  end adjust or  top adjust
Typical failure modes (after many years of service):  total failure: most likely due to the fullwave bridge rectifier or output opamp.  non-linearity: most likely due to the charge pump circuit.  inability to calibrate: most likely due to the charge pump circuit.  noisy output: output opamp is failing –or– input signal is noisy –or– board mounted isolated power supply(ies) are failing –or– loop resistance is very high –or– it could be that your mADC reader (DCS, DAS, etc) is misbehaving.
Repairable: Yes! Call us at 877-616-0600 for an RMA number.