From Tony's Train exchange
Special Application Notes
For BLI Switchers and Proto GP9: We found that sometimes a 12 Ohm 1 Watt resistor (Digikey P12W-1BK-ND or equivalent) placed?between the PowerPax and the programming track in series with ONE of the PowerPax output leads solves the problem. With the resistor installed, all three systems were able to read and write CV values correctly. This may be made as a permanent change to your programming track setup if it does not appear to affect the programming performance of other decoders.
While this DID NOT work for me it might for you. ? But do not put a resistor BETWEEN THE TRACKS OR THE LEADS THIS WILL FRY SOMETHING.
Adding a 12ohm resistor in SERIES with the track circuit being used for programing a loco will reduce the voltage at the decoder (presumably because "PowerPax" has higher output voltage than the specified loco/decoders can handle). This is different to adding a 1000ohm resistor in PARALLEL which will reduce the circuit resistance for acknowledge pulse the decoder creates by pulsing the loco motor when a CV value has been successfully programmed. So these must be solutions for two different problems.
Jan
