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3 replies

Second Radio board burned out in FastTrack O36 LH switch

J Johnny_OOGR Forum Member

All, maybe Gunrunner John in particular, I replaced the TMCC radio control board in a FasTrack O36 LH switch (6-81947), and you can read about the problems it was giving me in Interaction between Lionel CW80 and TMCC/Legacy control topic. The new 2nd TMCC radio board worked great on the bench. Replaced the metal backing of the switch, worked great. Install, but not fastened down, on the layout, worked great. Fastened down the remaining track sections around it, worked great. Fastened down the switch itself - OH, OH! No more function! The straight position seemed unsure of itself, chattering and so forth. Hurried across the layout to the transformer... TOO LATE! When I removed the switch and opened it up, same burned out transistor on the radio board near the connector cable to the control board!

I am VERY reluctant to put in the 2nd TMCC radio control board till I find out why the replacement blew out again.

In another post on this forum about remote radio control updating manual FasTrack O36 switches, there was a comment about +5VDC from the control board of the switch to the radio board. Also a comment about the control board needing to be updated. I found and measured the 7805 voltage regulator on the control board but I did not see +5VDC at its output.

Does anyone have at least a pinout of the control board to radio board cable so that I can see what signals/where the voltages/control go in/out of the radio board?

Again, Thanks to All.

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RC Richie C.OGR Forum Member SUPPORTING MEMBER

The fact that you say the switch was "installed" on the layout, but not "fastened down" and worked great, but then failed only after fastening it down could be a clue as to what could be happening.

By "fastening down", I assume you mean screwing into the track. FT switches need to lie as flat as you can get them and even slight overtightening the screws can cause issues because you may be compressing or distorting an inside component against something else and causing a short. 

If the adjacent track sections screw down fine and there are no issues ("Fastened down the remaining track sections around it, worked great") then I would just leave the switch installed, but not screwed down, and hopefully, that will resolve the issue. It's not mandatory that every piece of track be screwed down. If the track is laid properly, a screw in every 3-4 sections, especially FT which is so stiff,  should be fine.

J Johnny_OOGR Forum Member

Richie C, thank you for responding.

Yes, that is what seems to be happening, i.e. a short of something internal, destroying the radio board. But, the BIG question is: should that happen!?

There is some type of "barrel" (forgive this non-mechanical engineer for not knowing the correct term) around the fasten down hole(s) of FasTrack , and I do not tighten them enough to distort the track, just snug up the wood screw "conical" section to the hole for it.

My layout is being built on plywood, so for the moment I will leave off the metal plate on the switch bottom, leave out another new radio board (until I figure out what could be shorting), and control the switch with an SC2 (besides the manual remote control).

'Til then...

cjackcjackOGR Forum Member DIGITAL SUBSCRIBER

Well…What’s on the top of the radio board that might touch the metal bottom plate when you tighten it down. I would have to be some metal showing on a resistor, etc. Then put a piece of black tape over that part…or better still, put a layer of black electrical tape or gorilla tape over the inside of the bottom metal plate where the radio board could touch it.

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