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I’m repairing a MTH 30-1409-1 0-6-0 Imperial USRA Steam Switcher w/Proto-Sound 2.0.  The tender was hooked-up to a different engine to diagnose issues with the other engine and fried the good PS2 board (wasn’t me and it happened years ago).  I’ve already spent a lot of time replacing burned MOSFETs, diodes, etc. and decided the board in question is a total loss.  I have two good PS2 3V boards but one is a B&O GP40 Diesel and the other is a NYC 208 Steam.

1)  Are PS2 3V boards interchangeable between steam and diesel? One idea is to download a new sound file into the B&O GP40 Diesel.

2)  The NYC 208 Steam board has different connectors than my repair board or the GP40 diesel board.  The NYC 208 Steam uses HRS (HIROSE) DF3 2mm black connectors, same as PS2 5v.  The other two boards use JST-PH 2mm white connectors.  Perhaps the DF3 black were early runs?  If I can use the NYC 208 Steam board then I will simply replace the tender connectors to JST-PH.

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yes as far as I know they are but there are different size ram in some ps 2 3 volt boards so as long as the ram is enough for your sound file they will work. ps 3 the diesel boards are totally different then steam. the largest ram on p s 2 is 2 meg max, if I remember correctly. if the ram is made by SHARP as marked on top the ic it is 2 meg. you just have to use the  dcs loader program and install the correct sound file for the engine you need

if you give me the item number ill put the sound file on here for you!

ps you can just swap the black and white connectors on the  boards will work the same type just fit the harness a little different you can heat them if your careful to soften the connector so they will come off easier, or if you know how and can be careful very careful a knife edge will pry them up. if you use a heat gun just don't heat the electronics only the soft white or black connectors, I have done it many times!l

email me here is the sound file



Files (1)
here is you steam sound file
Last edited by Alan Mancus

Thank you so very much for the useful and friendly responses!  I will work on the engine tonight and see what happens.  I have to get up for football games early in the morning for my sons so it might not get done tonight.  The tip on the 2 MB Sharp ROM is great and going in my notebook right now.

I couldn’t bring myself to cram the wrong connector into a board.  I have all the connectors and crimps to do the job right.

As a little background, I’ve been helping my father-in-law with repairs for about a year and a half.  He brought a flip-flop based E-Unit to me last summer because I’m a computer engineer and might be able to do something with it.  I fixed it and he brought me another 5. So far I’ve done about 15 but it feel like I still don’t know anything about the electronics.  The hardest by far has been the MTH PS2 5v.

I’m sure to have more questions and thank you again.


Images (3)
  • DSC_9619: JST-PH 2mm Connectors
  • DSC_9613: Work Desk
  • DSC_9617: Supplies
Last edited by tansqrx

great to hear thanks for the response getting back. have you ever had any luck repairing a ps2 5 volt board? yea I installed a ps 2 3 volt board in a challenger about 2 years ago or so and had to switch over to black  connectors. engine had a original 5 volt board That  died as a lot of them due.

been best running engine ever since.

thanks for updating us on your repairs 

I’ve had some success repairing the PS2 5V boards but on average I only get about 20-30% working again.

In order of easiest/most likely to succeed to hardest:

  1. Check the external 5V voltage regulator. It’s a LM2937.
  2. Check to see if the electrolytic capacitors have gone bad. Usually the top vent has popped or leakage around the capacitor base.  Will have to separate boards.
  3. Check for shorted wires
  4. Separate the boards by removing the Kapton insulation tape and MOSFET heatsinks. Desolder the 14 position .100” connection header.  This is by far the toughest because of the no lead solder and many of the pins are connected to large surface areas.  The large surface area acts like a heatsink and makes the soldering iron almost useless.  Use copious amounts of ChipQuick flux, solder wick, and solder sucker.
  5. Put on high power magnifying glasses and start looking for obviously fried components.
  6. MOSFETs like to fail due to static.
  7. Many of the really small SMD components are impossible to source. They usually have a 3 character code such as A7P, A4T, 352A, W2X.  If I’m able to cross-reference, there are usually multiple possibilities and many times out of production.  I’ve built-up a collection random components to experiment with
  8. If there are multiple component failures then the board is almost certainly a total loss. I compare this to a lighting strike where the failure(s) could be anywhere.  I use these to experiment with and soldering practice.


  • Repair #12. PS2 5V board with smoke coming from the capacitor area, as reported by the customer.  Completely dead.  I separated the board and found the 5V regulator wires had shorted and fried multiple components.  I replaced a few MELF DO-213AB diodes with a best guess.  The only markings were stripes which I found varies.  After messing around for a few weeks I gave up.
  • Repair #11. PS2 5V board with sounds but no movement.  Separated boards and found a capacitor loose.  Also found a short in the tender couple board.  Put back together and it worked.


I have more ideas than I have time but here are a few of them.

  • Create test harness for the 14 pin header. Attach to Arduino to run diagnostics.
  • Reverse engineer board test points and create diagnostics.
  • Recreate PS2 test stand (MTH has one for their repair tech) with Arduino, Raspberry Pi, or similar.

Questions for the Community

  • Can PS2 5V boards be swapped between steam and diesel like the 3V boards?
  • Does anyone have an internal pinout for the PS2 5V boards, i.e. the 14 position connector or PCB test points? Board schematics?
  • A common observed failure mode is a constant relay clicking when voltage is applied. I’ve tried several things but none worked.  I assume a relay failure or a transistor/MOSFET not providing enough voltage to keep the relay open.  Additional comments wanted.


Please add any comments.  I’m also working on three PS1 boards so I may start a separate thread for them.

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