Accidentally shorted an LED on engine - question on repairing it

No telling, best to just get an LED and sky-wire it in and see if it lights.  Each of those ditch lights is driven from a separate output on the RCMC, so it doesn't tell us anything if one is lit.

Lionel's parts listing is not that informative about the locomotive.

@gunrunnerjohn posted:

No telling, best to just get an LED and sky-wire it in and see if it lights.  Each of those ditch lights is driven from a separate output on the RCMC, so it doesn't tell us anything if one is lit.

Lionel's parts listing is not that informative about the locomotive.

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Thanks John! Will try a spare LED laying around and hope for the best. The lack of parts on Lionel's site was slightly less than pleasant XD.

A short may have damaged the board, but how could a short damaged a LED??

Looks like I got very lucky, soldered a temporary wire in and tested the LED, looks like it's still fine

You did indeed get lucky, buy a Lottery Ticket right now, should be a winner.

@lpb007 posted:

A short may have damaged the board, but how could a short damaged a LED??

Pretty simple really.  The LED is directly powered by the RCMC, but the RCMC does NOT have a common AC and DC ground.  So, grounding one side of the LED could have put way more voltage on the LED than is is rated for.  Grounding ANYTHING on modern Legacy or any MTH PS/2 or PS/3 boards is very bad for the health of the boards and the parts.

Thanks John.  I am glad I asked the question. I continue to forget about the grounding issue inherent in this design (i. e. lack of a common ground). SirCaptain dodged a bullet and had a great outcome.  Thanks again for your info.  Pat B.

Well, that "grounding issue" has basically migrated to most of the current electronics for MTH or Lionel.  TMCC and the older modular Legacy still had AC and DC ground common, but around 2010 when the RCMC showed up for Lionel, it lost the common ground.