MTH PS3 Help w/Diagnostic with steam engine that does not run

Large board in the tender is the main board. The smaller boiler board takes commands from the main board in the tender. It's possible to kill one or the other board and not both. Your symptoms are pointing more to a dead tender board. Boiler board may or may not be ok. If the drawbar connectors are loose the locomotive will not power up, but I assume you have already checked that.

Since you have the PS/3 test set, I suggest testing each of the two boards separately.  I presume if you have the test set you also have the "golden" boards that allow you to individually test the steam set?

Truthfully, I'd be looking very closely at the wiring with these symptoms before I started replacing boards.

Yep, I’d be looking at wiring, …especially grounds,…the later PS3’s with the 3/2 option are poorly grounded. On the bench, let a continuity tester be your friend, ….

Pat

Thanks all, for the quick response. I have many questions please bear with me.  I checked the wiring for continuity from pickups in the  engine to boiler board & thru the harness to tender board,hot & ground. Especially ground. I see no pinched wires, loose plugs. Questions on the test unit. When golden boards are mentioned. Do they mean a known or new  good board ? Does the engine being tested have to be loaded in my DCS unit.? Lastly I have the harness's for the tender P150 &151 But I don't have a P154  Tdr SW jumper to be installed at P77 on the tender board is that one needed ?  I do have 1 new tender board but hesitate to install it  don't want to see magic smoke.

The PS/3 test set needs a set of "golden" boards, they're loaded with a special test software load.  You can use any PS/3 boards and just load the test chain files.  I bought mine when I got the PS/3 test set in 2013.

It would be unusual for a bad boiler board to take out the tender board, normally the enemy of the boards is pinched wires, shorts to ground, etc.

You don't need the golden board if the boards are good.  If they are bad you will know it.  the only time I use a Tender golden board is to test the boiler board if the tender board is bad.

Frankly, PS-3 can be more complicated to isolate and ground check don't always work.  Missing the PS-3 course puts you behind pretty significantly.

Test the boards following the instructions, if they work.  You have wiring, drawbar issue.

What amperage is the engine drawing?  If you have power to the tender board and no sounds/lights in tender even if engine is dead, you have a bad tender board.  If tender board is good, but engine still dead, your not getting AC to the tender.  G