Question to our resident MTH tech's about a rear coupler

Hi I would recommend trying a feature reset, sometimes a feature gets scrambled but can easily be reset with dcs remote, i have seen this work many times and correct the problem ! go into advanced ad due feature and then do engine factory restore !

I:\Instruction Manuals\RailKing\Steam\30ST12217I_2666 wPS2 FYS\30ST12217I.PDF (mthtrains.com)

Alan

I'd first check all the wiring from the coupler all the way to the board.  If that all checks out, the board is a likely candidate for the failure.

I'm surprised that the ASC Service Manual doesn't have the location of the coupler FETs for the 5V board.  You'll likely have to do this the hard way, trace back from pin-8 of the 12-pin connector on the PS/2 board and see which FET it connects to.

It is a single chip for both couplers in a difficult position to get to and not easily repairable.  Move the rear coupler wire to the front coupler spot and see if firing the front coupler activates it.  Don't think I have seen a coupler failure on a 5V board.  Not saying not possible, just seems very rare.  G

Thank you guys for the replies.

Alan: Did the reset as per the owners manual this morning....got the 2 whistle blasts confirming the reset had been successful. Everything works fine......except for the firing of the tender coupler!! No change there.

John: Will follow your advice and start the "tracing game" till I find where the coupler wires attach to the PS2 board. Once I have found this spot, the correct FET should/I hope become obvious, and hopefully I will be able to glean enough info from it to identify it, and order a replacement.

George: In my "tracing game" I hope to see where the rear coupler wires connect to the board, and if it is obvious there is a place for front coupler wires (these wires will be missing as this loco only has a rear coupler) I will see if I can swap the rear coupler wires to the vacant spots, and if I can get the coupler to fire open then. Fingers crossed!!!

Thank you guys, and I will report back after the "open heart surgery" on the PS2 board later today. I can tell you I am a bit nervous undertaking this type of surgery, all on my own!!!

Peter......Buco Australia.

@GGG posted:

It is a single chip for both couplers in a difficult position to get to and not easily repairable.  (  Move the rear coupler wire to the front coupler spot  )   and see if firing the front coupler activates it.  Don't think I have seen a coupler failure on a 5V board.  Not saying not possible, just seems very rare.  G

George , since the Allegheny doesn't have an activating front coupler do you just reposition the pin of the rear coupler to what pin number location on the connector ? 

At MTH I made a harness with a 9v battery to test couplers.  Just unplug it from the harness and momentarily plug in the battery and see if the coupler opens.

Afternoon Gentlemen:

YES, YES, YES!!!!!

Houston, we have lift-off!!!!

Took Gunrunner John's advice and started inspecting and testing the wires coming off the soldered tabs that attach to the fine copper coil wires on the underside of the coupler. Found the problem almost straight away.

Even though the brown wire looked well soldered, it wasn't, and had completely broken away from the small blob of solder, but was just sitting there looking like it was properly soldered. Gave it a small tug, and there it was, completely detached from the coil wire connection.

Trimmed the black tube back a little to allow more free length in the pink and brown wires to the coupler, paired the insulation back on the brown wire, and exposed the very fine inner wires. Heated up the trusty soldering iron, tinned the bare wires, and then placed them on top of the existing blob of solder. Held them in place with a small bamboo skewer, and then touched the solder blob with the iron.

You probably can tell which is my attempt at soldering the broken wire, but I wasn't competing in any soldering competition!!!! Bottom line.......the coupler is working a treat again!!!!

Buttoned the chassis back onto the tender shell (making sure not to pinch any of the wires), plugged the tether into the loco, and off it went perfectly!!!! The tender coupler fires opens superbly every time, even on the run.

I am one happy camper, and the Allegheny 2-6-6-4 steam loco is back in full service on the Buco layout.

Thank you Gunrunner John (and GGG) for putting me on the right track (so to speak).

Peter (Buco Australia)

We love success stories.  As a bonus, I even learned something about the 5V board, I didn't realize they used an oddball part to fire that coupler.  I've never had to replace one, so I never went looking for it.

Yes if you placed the rear coupler brown wire into the slot on the 12 pin for a front coupler, then you could use the front coupler button to activate the rear coupler.  In fact MTH used this sequence for some AUX tender set ups.  Rear for main tender front for aux.  Vice a switch.

You always need to test through the harness wires with connector out of the board.  Continuity may work, but carrying a load usually finds the defective joint.  Even bad solder joints under heat shrink at the 2 pin connector can bite you.  G