Testing a Motor Driver board DCDR K-line RS-3

Two of the pins on the 4 pin connector go to the track. The other two go to the motor. Make sure you can measure from the connector to the rollers and frame or  check for AC with the engine on the powered track and voltmeter on the red and black wires. Might just be a burnt wire.

Pete

Tested and check out fine.  Also got correct voltage readings at the rectifier output.

Have you tried running it in conventional? I would think if it smelled of burning it would be obvious on the board if it was the DCDR. As for your previous question, you could replace this with a Cruise M. The fact that you have no lights means it could be the R2LC or power to it.

Pete

The no lights seems to exonerate the DCDR, nothing on that board would turn out the lights.  I'd be looking to test the R2LC in another locomotive.  If that's good, look for a cooked trace on the motherboard.

Got It!  Tried GRJ's idea first (shoulda thought of that meself) and found the R2LC worked fine.  When I first started this, I assumed all of the AC current went into the DCDR, was rectified to DC, and then fed to the rest of the components.  Now I realize that all of the AC goes to the Motherboard and from there is distributed to the rest of the components.  Duh.  So I took a closer look at the board (691PCB10B1) and found that some of the laminate that covers the traces was 'bubbled' but no burned areas.  I scraped some off and found the trace to be bright and shiny but in putting a meter on one section (the first trace from the AC input), found 0 resistance.  I carefully soldered a small wire to replace the trace and voila, she powered up.  I kept it under power for a few minutes with no burning smell or other fault.  So now my question is this:  do I replace the mobo or let my repair stand?  Do you think it was a poorly made mobo or was there a short that caused the trace to fail?  And why is the pressure switch of my new heater only working intermittently?  (You don't have to answer that one.)  Thanks in advance for all advice.

Bobby

The motherboard should be OK now. This is a problem with some of K-Line engines. Instead of wiring the pickup rollers together, they use the motherboard traces to connect them together. Those traces are not big enough to handle the current for the whole engine under load should one roller lose contact with power. The solution now is to connect all of the pickup rollers together with the red wire to the 4 pin connector on the DCDR plus the red wires to the motherboard. 

The big problem with the K-Line MB was that when the locomotive derailed, sometimes a roller was on the outside rail, and the other on the center rail.  Then the MB becomes a fuse.  That is much more likely to have been the cause of the problem.  The fact that it derailed and then you got smoke suggests the above scenario.  Truthfully, the trace that I've found cooked on the K-Line MB should have easily been able to handle the couple of amps of the locomotive in normal operation, just not when you connect it across 10 or more amps direct from the transformer.

That is likely what happened but if the rollers had been wired together the wire would have been the fuse, one with a higher rating, rather than the circuit board.

Pete

Correct Pete, if the rollers are actually wired together with the typical #22 wire, it usually manages to trip the breaker before cooking the wire.  I think K-Line was trying to be "neat" with the wire layout and didn't think through the operational issues.  I have taken a few passenger cars apart, and even one locomotive, where the wire was indeed fried from a derailment.  In the passenger cars, the wire looked more like #26 or #28, so it was no surprise that it died.  The locomotive was running on a layout with parallel 180W bricks, so there's no mystery why there was enough current to fry the wire.

Took your suggestion and added the 'jumper' wire between the pickups.  She's running like a champ now, thanks to everyone's help.  Gosh, what a great day; I even fixed the house heater.  Happy hollerdays, and thanks again.

Bobby