Like was mentioned in a previous discussion - yes, the PM42 needs a power supply to actually detect a short and operate, however since relays are used there should eb continuity between the input and output with no power applied to the board. The power is neeed to activate the controlling electronics to actually detect a short and pull in a relay, opening the circuit, or switching it for a reverse loop.
Default trip setting is 3 amps though, too much for a PowerCab, and the settings can only be changed via Loconet. If you MUST have circuit breakers on a 1.7 amp system, NCE has CP6 which uses 1 amp light bulbs. IMO the money is better spent on the AUto-SW so you never ever accidently program all the locos on the track. It automatically directs the PowerCab output to a seperate programming track when you enter programming mode. You can do this with a toggle switch as shown in the instructions, but you can also forget to throw the toggle. If you find you need more power and upgrade to teh SB3a Smart Booster, then you cna add individual power district short protection since it's more likely that you will have other operators using a second or third throttle. Plus 5 amps is enough to cause damage in some cases, so restricting any portion of the layout to 3 amps or so is good protection even in a solo environment.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Do you have a separate power supply connected to pins 3 and C? The PM-42 requires an independant power supply.
Regards,
John
"You are what you eat," said a wise old man. Oh Lord, if it's true, I'm a garbage can.
Are you sure you have the rails ocnnected to the right pins? The PM42 is really just relays which have the contacts mechanically closed unless there is a short. In other words, a PM42 not even connected to anything should show continuity between say 4 and E.
As to the usability with a PowerCab - not really. The PM42 needs a Digitrax throttle to set the trip current levels. The default is beyond what the PowerCab can produce. Even having breaker districts with the 1.7 amps of the PowerCab is kind of pointless.
Hello all, Just got my PM42 installed & wired, I have check my wiring 4 times to diagram provided. I did use both grounds b & x returning to power supply. Board lights up and I have power in from booster to pins 4,7,8,11,12,15,16,&19. There is no power to rails out of the pm42. I only have 2 outputs currently installed to rails and the other 2 are disconnected. No power on any output. Any ideas? I have another PM42 that I can test with if necessary. Also I was told By shop I could use NCE power Cab With PM42, From posts this looks untrue?