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Background, I recently was modifying an engine with various parts I was able to source. I had on hand 3 different LCRU 2 boards and an ERR Sound Commander 1.5 and all the cabling. What I ran into was the dreaded works in conventional, but the sound commander goes into conventional mode when the system is working from TMCC. I saw previous threads on the serial data buffer using an emitter follower circuit, but decided there must be a way since all 3 LCRU boards did the same thing. Then I found the secret- R33, Lionel used a 10K Ohm resistor between the processor and the output data pin connector. 10K is extremely safe to ensure not blowing the processor pin, but at the same time, very limiting drive wise for any serial data device attached that basically must have some sort of low impedance buffer. So all I did was swap that 10K surface mount resistor for a 1K (borrowed from a broken and parts robbed lionchief remote) so at least I'm using genuine Lionel parts when I mod.

The factory (R33) resistor was labeled 103 (10K), the replacement is 102 (1k)

LCRU 2 resistor mod [R33)

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  • LCRU 2 resistor mod (R33): Modifying the serial data out resistor (R33) from 10K to 1K
Last edited by Vernon Barry
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Again, given that I had 3 different LCRU 2 boards on the bench, 1 was in the AEC switcher, the other 2 were straight from Lionel Parts I bought (because they happened to be the cheapest ones) 691PCB1001 but all 3 used the exact same 10K resistor for R33. I modified all 3 boards and tested them. I also didn't mention, I also used a brand new ERR Railsounds commander http://www.3rdrail.com/err-3rd...lSoundCommander.html and it too was not driven properly by the factory LCRU 2 and the 10K resistor. Just sharing, this wasn't a one off test, this was pretty much a smoking gun that if you have or consider using an LCRU 2 (and why not mod that old engine and add TMCC?) well, to get sounds working, this is a pretty sure bet mod.

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  • 341957691PCB1001: Notice for the smoke output the smaller TRIAC just above the white optos
  • 262066108583256: This is the one in the AEC switcher, it has the larger TRIAC (unused in the switcher) typical for smoke units
Last edited by Vernon Barry

Also, while on the topic to consolidate mods- Taken from here https://ogrforum.com/...ector-pinout-diagram

gunrunnerjohn posted:

The LCRU has a positive output from the lighting triac.  It will require a .01uf capacitor across the light output to trigger the triac using just an LED.

 That explains why I was frustrated with my LED headlight mod not lighting, so when I started probing and the extra capacitance from my body (finger) touching the positive lead of the LED it flickered and came on as long as I was touching.

 

Last edited by Vernon Barry

Yes, I bought them in November, but no, it was after the sale. Sadly, I was knee deep in my learning of lionel parts and systems used and was completely unaware of what the LCRU2 was at the time. I did place and got a good order in during the sale, but didn't prep or know enough in advance to know all the boards I wanted to play with.  Oh well, $50 isn't too bad for what this board does and is. Perfect for slapping in that old 20XX series tender and loco to give you TMCC. My particular project is a 2035, but looking for other fun locos that are not of great collectors status, but good runners and worthy of spending a few $ on.

Makes perfect sense, the sound boards have an opto-isolator on the input serial data, and a 10k resistor doesn't provide enough current to drive it.  Good to know, I confess to having never tried this, but I'll remember this if I decide I want to.  Of course, my go-to solution is always not to modify the factory board if possible, so I'd probably use the serial data buffer.  It would work the same with the LCRU2, just have to find the 5V source to power it.

R2LC Serial Data Buffer Schematic

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  • R2LC Serial Data Buffer Schematic

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