We have a problem with a Star manufactured High Flux Chiller.

The chiller operates on R22 and uses a Danfoss PHTQ expansion valve. The PHTQ is controlled by a Star PCB which has failed and the board is apparently no longer manufactured.

As far as I can tell the board takes a signal from a thermistor in the heat exchanger and the valve opening is controlled by this. I think the logic of the High Flux is that it is almost flooded and the heat exchanger is like an LPR vessel.

Can anyone expand on the operation of the PCB so we can come up with some sort of alternative. At the moment we are not really getting any info from the manufacturer.