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Hello I had a derailment I didnt notice that was being powered by Fixed 1. This is an original TIU (No revision number on it). After the derailment I do not get red LED light. I was able to get around this by using an auxilliary power supply and switching to Fixed 2. The variable channels work correctly. I am doing a major layout revision and thought I would check this more closely. This early unit has no fuses I can see. When I meter fixed 2 I get read 0 ohm continuity on both red and black  in to out. fixed 1 shows red continuity but black is open. I thought I read in a long ago post that this revision TIU cant be repaired. Any suggestions on this would be helpful.


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hi you might have a shorted tvs diode on the out out side take cover off and check 4 diodes there is one on each channel output, disconnect one end and check continuity if 0 ohms diode is shorted and needs replaced, your track short frequently causes  these diodes to short! if you disconcert and find the shorted one while disconnected power up and you'll probably find tiu now works, you don't want to operate it like this but is ok for a test! if you need repaired let me know!


I see plenty of TIU that the terminal melts and insulates the connector from good contact on the input terminal.  Of course First TIU had a solder joint not, nut and thread connection.  BUt for later models, make sure terminal nuts inside the TIU are tight.  Any signs of melting plastic means a high resistance point.  G

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