I have a MTH Z-4000 Transformer.

How much voltage? My first run Z4000 did the same thing but with a few lighted cars on the affected output track would reduce to zero. It's now used on a track that has lighted lock-ons so the voltage always goes right to zero when in the lowest position.

It runs up to 10-12 volts.

Add a lightbulb load to the output.

Otherwise you are taking it apart and adding tiny surface mount sized capacitors to the power and control board.

@jag8630 posted:

The left lever, dial on my Transformer shows residual voltage when i never move it. any ideas how to fix that.? or what is causing it.

Again, this is semi normal. You cannot "adjust" this out, it is not caused by the throttle pot.

How can I know that? You cannot use a Z4000 transformer with an out of adjustment throttle pot because the system checks the position of BOTH throttles on power on, and will not allow the transformer out of power on self test (POST) until that condition is achieved. Again, the throttle pot much achieve the O or off condition setting to even turn the transformer on and begin using it.

@jag8630 posted:

It runs up to 10-12 volts.

If it is that high, that's more than just a voltage leak, that either is crosstalk between your output channels- remember- the meter is always reading the output and yes, the manual warns never to short the 2 outputs together, but the meter can read voltage if your wiring or track somehow is backfeeding the channel.

Again, does it do this with no wires attached to the transformer?

If so, then it is possible than channel is damaged. That may be a main power control board issue.

Also i do have 6 lighted turnouts.

Vernon is on the right track. Mine would only jump to 2 volts or so. Just high enough to not shut down PS1 engines. Adding a lighted car or lock instantly dropped it to zero.

Yes it does it with no wires attached.

@jag8630 posted:

It runs up to 10-12 volts.

I have several MTH Z-4000s.  For the units that show a low voltage leaking (~2 volts), the lighted lock-on works great.  However, if the transformer shows no lower than the 10 to 12 volts, you will need to open it up and do a small repair.  I had to do this on one of mine.  The bottom screws are Allen style heads and are quite deep (you make need to get a long Allen wrench).  There are gears driven off the handle.  There is a mark (black or red) on the gears for making the alignment, however, I had to readjust so I would get a lower setting.  The risk is setting up the gear teeth too far one way so the manual stop on the handle is not engaging before the potentiometer pot runs out of travel.  This could damage the pot.  This adjustment will also reduce the high end voltage a little bit, but it is not uncommon for these transformers to output 26 plus volts.  Way more than one needs.