Issue with Variable Channels

@Yank2304 posted:

I am helping a friend with his TIU and his fixed 2 input shorts out and no power to the track - def an issue with the TIU - Changed all the fuses and issue still happens

however every other output works - fixed 1, variable 1 and variable 2.

My issue with - with this particular tiu - his variable channels which are NOT set to fixed - power up without instructions via the remote on the track page of the remote.  Once I vary the voltage - that’s when it goes to variable - but on every other tiu I have - my variable channels are always at 0 volts unless I modify the voltage via the remote.  Any suggestions?

#1 dead short on any of the 4 channels is most likely a failed output TVS diode. Easy to repair and fix. Cut the leg of the suspected shorted diode and if the short on the input clear- replace that TVS diode.

#2 Being the variable channel does work and vary the voltage, this is simply a setting issue for that channel. Simply reset the TIU to factory defaults and the problem goes away to how you "expect" it to work.

Thank you the detailed response.

Can you help guide me the location of the affected diode and where I can buy a replacement?

Topic on the TVS diodes 1 for each channel

https://ogrforum.com/...0#146001355087073240

Another post with an original picture thanks to @gunrunnerjohn

https://ogrforum.com/...7#129533723648698317

Fixed channel 2 is D501

Again, thanks to @gunrunnerjohn for the original picture in the previous linked topics.

And his picture again, with an edit highlighting D501 for Fixed2

Offically, MTH parts and Sales has TIU parts, however, this being generic, you can get the TVS diode from many electronic parts suppliers and even the auction sites. Oops, forgot the link https://www.mthpartsandsales.com/

Keyword search TIU on MTH parts

However, just google the part number and you would find tons of suppliers 1.5KE33CA

If replacing tvs, it's recommended to go with higher voltage rated (36 or 39 instead of 33) 

Wow extremely helpful - thank you everyone!!