TIU What Not To Do

I don't believe that either pin of the aux power is common to any of the inputs or outputs.  There is no continuity to any of the output or input banana pulgs.

Have you checked the internal 20 amp fuse for var #1?

Rod

8 power supplies properly phased..

can we see how you are accomplishing this?

pics and a schematic

John,

I don't believe that either pin of the aux power is common to any of the inputs or outputs.

The problem can occur if a Z4000 handle is powering a TIU channel input and the 14 volt output of the same Z4000 is powering the TIU's Aux. Power port.

If the polarity of one of the two outputs of the Z4000 is reversed with respect to the other output going into the TIU, a short circuit results in the Z4000 itself.

I've never tried that Barry, but that's interesting input, thanks! Obviously, no opto-isolation inside.

When I use the aux power, I always use an isolated power source, eliminates any possibility of such issues.

Guns,

   I agree I always use an independent power supply for the TIU, eliminates problems and opens up options.

PCRR/Dave

John,

When I use the aux power, I always use an isolated power source, eliminates any possibility of such issues

Each of the layout's 3 TIUs are powered by Z500 bricks, scrounged over the years from train shows and starter sets that have "passed through".

The bench TIU is a recently-acquired Rev. L that is powered via a USB connection to the PC. I have another Z500 on hand to test non-Rev. L TIUs.

I've had good luck with laptop power supplies, I have a bunch.  The TIU seems to be quite happy with DC as well as AC.

John,

Marty F. and I found one weirdness when using DC for Aux. Power and AC for channel power on Fixed #1, or vice-versa. I forgot which and the opposite worked fine.

PS2 or PS3 engines came up in conventional mode when attempting a sound file transfer.

I remember something about that, I haven't encountered it.  My operation is strictly AC on the control channels and I used AC or DC on the TIU power.

I do note that the DCS manual says AUX power is 12-22VAC at 1.5A, so I suspect I'm skating on somewhat thin ice.  I believe I looked and the aux power appears to go directly into a bridge rectifier, so I thought it probably wouldn't know if it was AC or DC.

Guns,

   Simple fix, use the Radio Shack power supply to power the TIU, never any problems in this manner, and they are not expensive.

PCRR/Dave

Why buy if you have something you can use for free?

It appears to me that center pin of AUX PWR & BLK Input wire on VAR1 go to the same terminal on the bridge rectifier in the TIU.  This constitutes connecting the secondary of two different power supplies together at this point.  Why is no caution statement necessary concerning making certain both power supplies are correctly phased?  Regardless of transformer used for AUX Input, someplace up the line the primiary of each supply must be in phase. What don't I understand about this subject? 

Are you sure that it's not the black input wire from Fixed #1 going there?  Since you can power from aux or Fixed #1, it makes no sense that it would be associated with the variable channel.

The phasing statement is not actually true.  As long as the other side of the two power supplies never have anything in common, the phasing doesn't matter.

This is the same as running accessories on a layout with a separate transformer.  Even if you share a common, if the hot lead never goes anywhere but to the accessories, it won't create a problem.  That's not to say I agree with the practice, but it's done all the time.

There's microswitch in the Aux. Power port that deselects Fixed IN #1 as TIU power if there's a plug in the Aux. Power port.

Thanks...knew it wasn't a relay but had to be accomplished.