voltmeter hookup

 I've gotten my dad's old trains out of the boxes that have been stored for 50 years and building a layout at 74 years of age.I have two old ZW transformers from the 50's and I am trying to find out if  I can hook up a voltmeter to monitor the output. Also, do I need to have a circuit breaker on the ZW's. If either of these can happen, then I need a wiring diagram. This is my first time an a forum.

Original Post

Welcome to the forum Dundy.  Sage advice and experience is on it’s way... lots of it here.  The gear you describe is about average age around here it seems,   Someone will have the info you seek.  You are correct, fast breakers are always recommended along with bi-directional TVS diodes for additional electronic protection should you go down that road in the future.  Once you learn about command control it’s addicting.  Enjoy the forum.  Enjoy the journey.


Ammeters are wired in series, voltmeters in parallel. A quick search for TVSS and circuit breaker will glean a plethora of information.

A search for "1×AC 20V Analog Panel Volt Voltage Meter Voltmeter Gauge 44L1 AC 0-20V" on eBay will connect you with one I bought. You didn't mention an ammeter, but IMHO it is no less useful than the voltmeter.



Photos (1)

Welcome, Dundy! 

My first suggestion is to do a thorough inspection of the ZWs.  THIS IS THE MOST IMPORTANT STEP!  Most transformers of that age need a little TLC, or at the very least a good visual inspection of the power cord, internal rollers, and internal circuit breaker testing.  With a faulty (cracked) power cord and/or faulty breaker, the risk of a fire is real.  If the rollers are bad, you can do permanent damage to the coil windings of the transformer.  If you are not comfortable with making the repairs yourself, it is worth every penny to have a trusted repair guy do the work.

A gentleman named, Kent S has a wonderful website with a very detailed walk-through of the inspection process (and repairs if needed) for a ZW.  Click this link to go to his webpage:   http://www.tranz4mr.com/ZW_Checkout.html

I'll second Gilly's advice on the meter wiring above. 

The transformer's internal breaker is to protect the transformer, and not necessarily the wiring or trains on the track.  That can be accomplished though -  the best practice is to also install a circuit breaker in-line with the power to the track.  Will you be running conventional postwar trains or more modern trains with command control?  Modern trains that have sensitive electronics (circuit boards) also require TVS (transient voltage suppression) diodes installed between the common terminal and the hot/power terminals.

Dundy posted:

The info. so far has been very,very helpful. I forgot to mention that I am O gauge, running the Conventional way. Also, where can I buy DC ammeters & voltmeters. Where should the circuit breaker be placed?  Thanks again.

Conventional O gauge is typically AC, not DC. Certainly your ZW is all AC.

FWIW the DC versions are also readily available on eBay.

Dundy posted:

The info. so far has been very,very helpful. I forgot to mention that I am O gauge, running the Conventional way. Also, where can I buy DC ammeters & voltmeters. Where should the circuit breaker be placed?  Thanks again.

The in-line external circuit breakers can be placed in series on the power line (A, B,C, and D) in the same way as the ammeter in the diagram above. 

I’m addition, it should be noted that a bad internal breaker can not be covered by 4 good external in-line breakers. Why? Because theoretically, you could have 4 in-line breakers rated at 10 amps all handling loads of 9 amps. The total current draw on the transformer would be 36 amps, far more than the transformer can handle with out damaging itself. 

Lube everything! Oil and especially clean out old grease before it grinds up a gearset.  (Old grease hardens, chunks into grit & will do damage)..Lots of lube choice and cleaning threads.(motor oil is ok for now)  NOT WD40, you may clean grease and stuff with it but it is not a suitable lubricant here.

To use two ZWs together safely you also must phase them together to avoid overvoltage (like double it) and some other issues.

There is a Lionel made video on "phasing two or more trasformers to be used together" I suggest watching.  It is pretty informative about about the whole process of changing wall plug AC to low volt, and ac cycling, etc.. Not too long and just involved enough to "really get it" on ac vs dc .  (Even if you don't use both, you will learn and brush up, Mike is easy to listen to imo.)

There are also quick and easy approaches and higher tech ways of checking.  You could just learn the easy way (both shown) but you won't learn why you are doing it.

You need a low volt range meter for it to be worth it. Don't bother with a 120v meter for use with our usual 5-25v.  I look for a 25-50v face

Put transformers on a power strip that has a breaker.

Internal breaker is really for the transformer. So fuse or breakers as noted on outputs, and with ZWs I'd stick to 12g stranded wire to amp meter, then again to the track, or as a "bus wire" to multiple 14g drops from track. (1 long & fat to feed multiple short & thinner wires; for best distribution)

Clean the old track well, consider new. It really does make things run better.

Please read up on a few modern choices here before you buy.  In fact, ask about everything & talk about everything. It will save you from yourself even when you're sure your right

"Still trying to not shoot my eye out"


"Nursing insomnia one railcar at a time"

My aroma therapy? Smoke Pellets.


Add Reply

Likes (1)

OGR Publishing, Inc. PO Box 218, Hilliard, OH 43026 330-757-3020