No Signal from TIU Variable Channel.

Checking fuse is easy but simple test would be to power the VAR (make sure TIU has power via Fixed 1 or aux port) and see if you have voltage out.  Not uncommon to have a channel go bad though.  G

For the Rev. L, a single channel DCS signal failure is usually the 74ACT244 signal driver.  That's the most common chip I've had to replace for that failure.

But he does not know if the VAR channel is powering up so that is what needs to be checked first.  G

It would be useful to have power on the channel, no doubt about it.   However, since he states he's using it in passive mode, just applying voltage to the output connection should power up the channel if the fuse is good.

G, thank you.  I have removed it from the layout and will power up that channel using the input terminal.  I have a Z-500 to power the TIU.  Will get to it tomorrow or Wednesday.  I have fuses so if no power on output, I'll replace that fuse.  Hope that is all it is.

Check that all the wiring terminal nuts are tight also, no melted plastic connector on that channel.  G