I was running two trains on parallel tracks,with both trains going different directions on separate Z4000 transformers and TIUs.
As one train was approaching the other, the first train had two or three cars derail and enter the approaching trains right away. When the approaching engines hit the derailed rail cars, the lead engine derailed. That set up a sequence where one engine and its cars were on one transformer track and the other engine and cars on the second transformer track in a derailment configuration. I believe that connection caused a spike (TVS) to go back to the transformer that was supporting the approaching engines. I can't swear that the red lights on both transformers came on, as I was more focused on turning each transformer off. After re-railing everything, I turned both of the transformers back on powering the TIU's and tracks and all seemed normal.
After about two hours operation, the Z4000 transformer, supporting the engine that derailed started to act up. When I started the two engine lash up, only the lead engine would start. I went back to the power strip and turned off the TIU and transformer and then restarted both. That didn't help getting a normal lash-up restart, so I moved both engines to another portion of the layout and they started as a pair and ran normally. That isolated the problem to a Z4000.
Then I went back to the Z4000 that was giving me a problem and when it was turned on, and as each throttle was advanced, it worked correctly. The light bulbs on the output channels of the TIU all illuminated. Then I turned the Z4000 off, and restarted the Z4000 again, however; this time moving the throttles had no effect on the LED readings of volts & amps and the light bulbs on the TIU output channels remain unlit, while both amp and volt readings both remained at zero. I turned it off again. On the next start, neither of the LED lights illuminated for volts or amps,and neither of the throttles would produce volts when advanced. Instead, I got a steady red light indicating a short, and a green light indicating the Z4000 was on and the cooling fan was still working.
Basically, what I have now is a Z4000 that will power the cooling fan and a short indicated by the constant red light with no amp or volt LED lights or output power. I removed all wiring to the Z4000 and the results were unchanged. Lastly, I used a different power source to plug the Z4000 into that was on a different house circuit, that was in phase, and still no change.
I know the TIU has built-in fuses to protect the TIU and trains from short circuits. The fuses are accessible by removing the TIU cover. If the Z4000 is also protected from shorts through the 12 amp circuit breakers, which never tripped or were manually reset, along with a red light circuit indicating a short, is there additional TVS protection internally that resets itself after a short?
I realize that the ability to use the transformer immediately after the train collision and for additional hours should indicate the transformer was protected and the short never damaged the A4000. However, it's hard not to suspect that the transformers inability to function now is not related to the short. I just want to make sure that I shouldn't have to use Mouser TVS fuses with a Z4000 and the Z4000 failure is just a coincident. Regardless, the Z4000 has to go back to MTH for repair.
Has anyone else had this type of Z4000 operation or failure? Does anyone know more about the Z4000 TVS protection?
Thanks, Moke Mike
