TIU voltage issues

Everything in phase?

If it were me, and going on your description, I would first disconnect all TIU outputs to eliminate any downstream wiring issues. If the problem goes away you know where to look.

If you still see the high voltage, disconnect all other power sources and leave only the source feeding port 2. If you don't use aux power to power the TIU obviously you need to have fixed one powered, just leave all TIU outputs disconnected to the track. See if you still see the high voltage on output 2.

Sounds like you may have an issue with the driver FET's on that channel.

Its definitely the FET as John says   Very common problem on Rev L   Always the variable voltage port   You have the high voltage when measuring but the symptom is more complex   When you apply a load, the voltage will go down to between 0-8 volts  We had one that displayed 45 volts with no load and went to 12 volts with a load   

Its fixable if you are a pretty good solderer    Otherwise a service tech can do it

Finding which FET it is can be tricky, sometimes I just replace all four of them, they're only a buck apiece.

Sorry for the slow reply and thank everyone for the information. I ordered the FETs and I will replace them

Ok, for those of us that are uneducated,,, what is an FET ?

Field effect transistor, one leg applies a bias and controls how much the FET lets pass. And that's about all I remember.

Interesting, a known issue with variable TIU channel. I may run my old 2026 from time to time so I'll keep this in mind when running conventional.

I assume the thumb wheel is controlling the FET bias?

@bluelinec4 posted:

Its definitely the FET as John says   Very common problem on Rev L   Always the variable voltage port

Was it something they did in the Rev L?

@BobbyD posted:

Was it something they did in the Rev L?

Not sure what they did but since we upgraded to all Rev L's we have had 12 failures on Variable ports  Funny thing is we dont use them as variable ports  We have them all set to fixed voltage

We also have been having failures in the variable channels, but ours run up to 8 hours a day every day, so they get a lot of use and voltage run through them.

One problem we do have, when set to fixed, often they revert to variable on their own, which can be frustrating, explaining to those running to check if it has gone back to variable, and walking them through a reset to fixed. Do that 5 times (5 TIU's in super TIU) and it takes a bit.

Ron, since the variable ports will automagically switch back to variable if you select the TR and change the voltage, it can be done by anyone with a remote.

You can also just cycle power to the TIU channel and it'll go back to fixed (until the next time).

It does seem that the Rev. L TIU's have had more specific issues with the variable channel FET's as well as much more frequently eating their 74ACT244 DCS signal drivers.

@gunrunnerjohn posted:

It does seem that the Rev. L TIU's have had more specific issues with the variable channel FET's as well as much more frequently eating their 74ACT244 DCS signal drivers.

That's unfortunate. We gave away our earlier TIU's and bought new "L" models because they were supposed to be better. ☹