MTH TIU Variable 2 - constant voltage

Do you have the port set to Fixed by chance

Actually, even if it's set to fixed, as soon as you use the remote to vary the voltage, it'll drop out of fixed mode and revert to variable until a power cycle on that channel's input.

It sounds like you have a shorted FET in the controls, that's a fairly common issue and you end up with full voltage out.

The port is not set to fixed.  if i have a shorted FET(?) what do i need to do to fix? i doubt i will use the Variable 2 port but still would be interested in why its not working - thanks for the information ad replies - really appreciate this forum

NOTE:  I moved this topic to the proper MTH DCS forum since it clearly is not talking about a traditionally sized toy train rather specifically is talking about the MTH TIU.

@ted K posted:

The port is not set to fixed.  if i have a shorted FET(?) what do i need to do to fix? i doubt i will use the Variable 2 port but still would be interested in why its not working - thanks for the information ad replies - really appreciate this forum

The FET's for the variable channels go down the middle of the board, there are four for each channel.  Usually, only one is bad, but finding it in circuit is tricky.  If I have to remote them to test it, I just use a new component.   I typically replace a pair of them, and if that doesn't work, I replace the next pair.  The FET's are fairly cheap, it's the labor of replacing them that runs up the cost.

is there a specification for the FET's or where can i buy them?  

The FET is the IRFZ44N at Digikey.

@OGR CEO-PUBLISHER posted:

NOTE:  I moved this topic to the proper MTH DCS forum since it clearly is not talking about a traditionally sized toy train rather specifically is talking about the MTH TIU.

Thanks Alan.  I’m sure I’m not alone in preferring to see the thread moved instead of being deleted.

thanks to all for the help - i will try replacing the FET once they arrive from Digikey

@Lehigh74 posted:

Thanks Alan.  I’m sure I’m not alone in preferring to see the thread moved instead of being deleted.

Yeah, but I and the moderators would prefer folks to post in the logical category instead of having to spend valuable time responding to the dozens of alerts we get from members over misplaced postings.

Thank you for pointing this out - i will try to do better in the future - hope it hasn't upset too many people