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Discussion Starter · #1 ·
Sitting and watching several people in a row in the last 24 hours on forums failing to properly understand or follow the instructions for the DCC/DCS wiring modification.

PS3 uses a tachometer to create a speed feedback loop with the controller and motor. If you somehow damage, break, cut a wire, have scratched the stripes on the flywheel, or basically anything that prevents the tach system from working.
Just like a failed tach sensor on a Lionel- or any engine with speed feedback control (EOB TAS) the controller first tries to ramp the motor to full speed because it thinks the motor just needs more oomph to begin spinning. Then, smartly because if the motor was stalled and would be damaged or burned out trying to g full power, the controller cuts power after a timeout period . This to a user looks like a runaway for a few seconds with an abrupt stop not commands by the user after a short period.

ENSURE YOU CUT THE RIGHT WIRE!!
For inserting a DCS/DCC switch or just enabling DCC mode by cutting the correct wire that forms a loop between pins 1 and 2 of the fine pitch 40 pin connector.
The railking line doesn't have a DCC/DCS switch so to operate this loco in DCC I had to clip a gray wire per the instructions.
Cutting the WRONG wire- like the grey wire- that goes to the tach results in runaway.
If you aren't sure, review the below diagram carefully and note on end of he connector has 2 ridges and one end has only 1 ridge. You want the wire that is at the 1 ridge end. Do not go on color alone, position in the connector is more important than color.

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Second part is, you must be EXTRA careful and never allow any PS3 wiring to touch frame ground or anything else.
Modern electronics rectify the AC track power coming in to DC and thus even negative return lines to the PCB from lights, fans, smoke units, motors, coupler, and switches are not at frame ground potential and any short to frame ground injects AC into the DC side of the electronics blowing them sky high.
 

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Not sure why anyone needs to cut wires. If there is no switch its just a matter of installing or removing the jumper.

Pete
 

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Discussion Starter · #3 ·
A lot of people are buying MTH Railking, and being DCS control system demand is insane and supply is zero, people are resorting to DCC.

This is going to come up more and more because Railkings didn't put in switches, color codes are not 100% standardized in MTH production and so people get it wrong and then wonder why, or worse, don't insulate or heat shrink the cut wire or sloppy soldering on a switch and smoke the expensive electronics.

Not sure why anyone needs to cut wires. If there is no switch its just a matter of installing or removing the jumper.

Pete
It's not a jumper like on a PS3/2 board stack or a PS3 tender board, PS3 "Diesel" boards have the 40 pin high density connector and in that, pin 1 and 2 has a wire that sure, if you had the tools and skill could be removed from the connector shell, but the instructions say to cut that wire. The problem is, cutting the correct wire.
 

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Discussion Starter · #4 · (Edited)
DCS/DCC switch details or connection points:

On a true PS3 diesel/electric, you have the main 40 pin harness and it's a black wire that makes a loop connection between pins 1-2 to enable DCS and bus be open circuit (floating) for DCC. MTH did not put a switch into the Railking versions of these engines and so the wire must somehow be modified. Again, the modification is to the 40 pin wiring harness. Yes, this can be a pain as that loop of wire is probably bundled and zipped and buried in the harness of a factory engine. You probably will have to cut zip ties and untangle the harness to ensure you are getting the correct wire and don't cut or mess with the wrong wire. The correct wire is identified as it will be at the end of the plug with only 1 rib and will be across the 2 end contact points that are pin 1 and 2. Do no go by wire color alone, verify and trace that wire to the positions in the 40 pin connector (should be nearest the 8 pin power and motor connector when plugged into the PS3 board).
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On a PS3 steam engine- yes, the boiler board either has a PC style header jumper over 2 pins, or has a switch connected with 2 wires to the same header pins on the tender board. Shorted is DCS, open circuit is DCC
Google pointed me to a picture posted by @gunrunnerjohn in the other forum
Picture by @gunrunnerjohn
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On a PS3 upgrade kit using the PS3/2 board stack set there is a jumper not unlike the PS3 Steam tender board.
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Discussion Starter · #5 ·
Follow up- yes, both people cut the wrong wire on more than one loco. Cutting the correct wire and repairing the grey wire restored correct operation.
 
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