Polar Mohr 71

Start by unsoldering them and measuring them. Then replace them.

Good advice but the resistor exploded and burnt the discription on the pcb :(

Contact the manufacturer for a circuit diagram or service manual.

The under lying problem is what caused it to "fry" in the first place?

At a maximum voltage of 630v the resister would have to be 400k or greater if the voltage can be applied continuously, to dissipate less than 1 watt. You could guess at double that? It would sure help if you knew what the circuit does. Could it be sensing a drive clutch voltage?

I really don't want to get into this discussion, but I have been fighting a Polar Mohr for the last three years. Mechanically, they are great machines, but their electrical control system is the worst, most obscure that I have ever worked with. To make it worse, their Distributer in the US refuses to provide any technical support. Why are you trying to fix a bad PCB, why can"t you get a replacement from Polar Mohr?

My solution is either dump the machine, or rip out the entire control system and replace it with a modern press control. After all, it is just a mechanical press, no different than a punch press.

The company I work for has many parts for these old polars. We may have what you need in our parts dept. Contact them at parts@absoluteprintequipment.com

the board # is (polar 012188) the resistor and capacitor are in series connected across to pins of connector 70.