Potentially Silly TMCC Feeder Wire Question

A PW-ZW has all four ground posts bused together, so you only need one connection.  Do NOT parallel PW-ZW outputs!  There will result in a direct short of the windings between the two wipers, and there's no fuse or breaker protection for that configuration!  Doing this will pretty quickly cook something in the transformer, and when you overheat the windings and burn the enamel coating off the windings, the transformer is junk!

Follow the red lines, if you were to connect the A & B posts together, note the current flow!  Note that the circuit breaker isn't anywhere in the current path!  It's the same situation for any of the A thru D posts, the circuit breaker in in the common U path.

I am not sure about the wiring for the ZW. But in general, using modern command control electronics with old postwar transformers is not a happy idea. The old transformers had very slow protection in the event of a short. Probably too slow to protect your TMCC or Legacy base. A modern Lionel 180W power brick is $80 on the used market. These have fast acting circuit breakers. Older 135 watt bricks can be had for $45. 

I know lots of folks are happy with their old ZWs. And as long as you never have derailments with shorts, there is no risk. But otherwise I'd keep a spare command base handy.

Don

Re: " I'd keep a spare command base handy" ,,, how is the Command Base in the circuit for a short on the track?

Thanks everyone! hat confirms what I suspected. I'm now up and running, however there is some sort of transmission issue in the TMCC commands, creating somewhat erradic running or functions on all locomotives I've tried. (new/clean fastrack, and analogue everything runs fine)

The wire from outside rail to command base is fine, and actually soldered on the track side. Could aging batteries in my remote control be the cause of this? (or the 9v in the tenders if they locmotives have them, I can't remember)

Sorry for the questions, I'm quite competent I swear, but for some reason the O scale regularly gives me trouble

The power brick is a good idea if that eliminates problems, I'll get one on the shopping list...

Dale Manquen documented the output circuit of the Legacy base years ago, see below.  I don't see how most happenings on the track would be a factor here, there is no continuity for large transients to affect the base.  Also, I truthfully have not heard any issues with track transients killing the command base.

@jpcanton posted:

The wire from outside rail to command base is fine, and actually soldered on the track side. Could aging batteries in my remote control be the cause of this? (or the 9v in the tenders if they locmotives have them, I can't remember)

 The battery in the tender is ONLY there to support the sound card with momentary power interruptions, it has nothing to do with TMCC operation.

The remote batteries can cause issues, Obviously changing them should be high on the troubleshooting list.

@jpcanton posted:

Could aging batteries in my remote control be the cause of this? (or the 9v in the tenders if they locmotives have them, I can't remember)

The 9v battery is there to keep the sound going if track power is interrupted.  It's most useful when running in conventional mode where you turn track power off to change directions.

When the batteries in a Cab-1 remote get weak, the red knob stops working well and eventually stops altogether.  Typically the button functions will still work.  If you find the speed hard to control, maybe needing to hit the direction button to stop since turning the knob won't do it, that is the classic weak battery symptom.

I used postwar ZW's on my layout with success. You NEED some type of fast acting fuse protection on the hot side from transformer to track protecting the electronics in the newer engines. You can always use a TVC on the hot to ground posts on the transformer as well for any power spike/surge.

John Will can chime in here as he has more knowledge on this subject than myself but this is how I operated my old layout for many years.

A fuse does not protect electronics, only transformer and wiring. The TVS is needed for electronics protection.

Well, batteries in the remote are swapped, the signal wire from track to command base is checked, and I still have issues. After more testing the throttle is a problem, but often the locomotives don't seem to be receiving function commands. (including just getting the things running)

The red light on the command base blinks like crazy anytime I give a command/input, so I suspect the remote is ok. And it is  on new batteries after all. The commands just don't seem to get to the locomotive. The layout is a single fasttrack oval of ~8x18 feet with one siding, with practically new and clean track, (plus all works ok analogue) so I can't see signal range being the culprit.

This might be the moment where I need to order a legacy setup, unless anyone has another idea?

Also- a big thanks to you all for the help! This is a wonderful forum...

It's possible the command base track frequency has drifted and it's marginal at certain points on the track.  You might be able to revive it by tuning the command base frequency.

See this post: TMCC Command Base not working

A fuse does not protect electronics, only transformer and wiring. The TVS is needed for electronics protection.

An in-fuse on the hot side from transformer to track will blow with a derailment, hence no power to the track, hence protecting the modern engine on that track.

Like I said in a previous post, I successfully used postwar ZW’s to operate my TMCC trains with no issues. I used 10 amp fast blow 2 mm glass fuses and never blew an electronics board on an engine, hence I protected the engines if something went wrong.

Hi all,

After spending another day stressing this, and remaining convinced I have a bad command base, I think I have discovered the problem: the house! The outlet seems to have an open ground, which I wouldn't have known since we are currently at my in-laws for quarantine. If I remember correctly this would skewer the signal?

Now the only problem is the whole room is setup with similar outlets, so I may need to wire in a new fixture or run an extension cord to a nearby bathroom with GFCI

Fingers crossed, I'm hoping to have results tonight!

Actually, the "house ground" is only used because it's convenient.  You can also tap off the command base and just run a long wire between the tracks of the carpet the layout to serve the purpose of the earth ground.  You can connect to either pin 5 of the serial connector or the outside barrel of the power supply connection.

Probably the easiest way to connect to the earth ground might be to use a 3-wire to 2-wire adapter and connect to the ground connection on the adapter.

Whoops. I fumbled the point. I should have said "protect your engines" but had the command base on my mind and said that instead. I love the ZW as much as anybody. But I am poor and can't afford to be frying engines or anything else. If you read through the electrical forum here, the protection theme runs through it like a river. But then I run DCS exclusively and those TIUs have well-documented failure modes. So maybe I am more (excessively?) sensitive to the protection issue.

Don

Hi all, just to close out the thread, it was indeed the house not the trains. I rand a grounded extension cord to the bathroom GFCI, and everything worked like it should right out the gate. A lesson in thought for me, as I was going sideways trying to diagnose the train equipment!

Re: "The outlet seems to have an open ground"

That's why I have an outlet tester in my tool box.  That problem is more common than I would like even in commercial venues that should be compliant with electrical codes.

JP, I'm curious ... if you loop a 3-wire extension cord around your layout before plugging it into an ungrounded outlet, do you have a good enough signal?   Slightly simpler than tapping Pin 5 or the ground prong of the power brick.