# how to check out ZW transformer?



## mywong23 (Feb 5, 2014)

I'm looking to buy a ZW.
I'm new to this forum, but have not yet found the correct search words
to find threads that could instruct me how to test a ZW.
(hopefully someone will post what search parameter to use.)

or instruct me what I can do with a multimeter to check if ZW is ok.

I read that carbon rollers and power cord are common things to replace.
but I could do that after I buy the ZW.

the ZW asking price is $90.

thanks to this group in advance.
mike wong

[email protected]

***********************************************************

btw, I'm planning to add a steam locomotive to my Lionel childhood set with Santa Fe diesel.
I bought a O gauge track pack. now I'm looking for another set of 022 switches, and a 2-6-4. with other questions that I'll post soon.


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## gunrunnerjohn (Nov 10, 2010)

Welcome to the forum Mike.

There are a couple of common replacements required for PW transformers like the ZW or KW.

Power Cord: This is very frequently required.
Carbon Rollers: Another very frequently required replacement, usually on the inside handles.
Rear Screw Terminals: These were cheaply riveted and work their way loose with age, replacement terminals are readily available.

To check it out, I'd take along a decent load and test all four outputs under load with a voltmeter. You can also check the whistle switch if you have a load on it, you should get a DC offset on the output when you hit the whistle switch.

If it needs work, I'd also try to bargain on the price a bit, ZW prices have come down significantly lately.


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## servoguy (Jul 10, 2010)

First thing is a good visual inspection. Take out the 4 screws that hold the top cover on and inspect the rollers and everything else.


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## GeraldNuss (Dec 31, 2013)

Listen for the hum. Unlike the rollers or the cord it is not easy to fix.


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## servoguy (Jul 10, 2010)

If it doesn't hum, it is not working at all. Now a loud hum might want to be avoided, but it really shouldn't indicate anything wrong with the transformer. All transformers hum.


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## mywong23 (Feb 5, 2014)

my findings:

the transformer has white lettering stamped on the bottom plate ZW (R)

1) original power cord looks in decent condition, pliable the whole length.
2) bulb under green ON cap was burnt out. replaced and now lights up with power.
3) carbon roller for the AU circuit is fairly worn;
the other three rollers are in fairly good cond.
4) the U terminal nut and post above the A post is missing.

5) there is faint hum - heard if press my ear onto bakelite case.

6) put multimeter on AU, BU, CU, DU posts: no voltage reading with handles in any positions  
7) put multimeter on AB, BC, AC, AD, BD, CD posts: no voltage with handles in off position.
however slight varying voltage readings when handles moved in various positions.

no wires appear to be hanging loose or unsoldered.

any other suggestions ?

I can post a photo if needed.
the carbon tracks seem normal for the amount of roller wear.

ps: the box has blue lettering printed: 11-55 and ZW 1 7 4


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## gunrunnerjohn (Nov 10, 2010)

Top suspect is the circuit breaker, as this would affect the voltage output from all the channels.


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## GeraldNuss (Dec 31, 2013)

Right, all transformers hum. But when they are loud enough to drive you from the room it is a little unnerving.


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## mywong23 (Feb 5, 2014)

1) with John's suggestion about checking circuit breaker, I thought I'd inspect the circuit breaker. I noticed one leg of the circuit breaker contact holder was broken, but since the other side's leg was unbroken, electrical continuity is unaltered and the operation of the breaker's contacts is still OK. 

at this time, I replaced the busted bulb in the "red" socket.

Eureka! 
now I detected variable voltage on each of the AU, BU, CU, DU circuits !!!
So it appears that a functional bulb has to be in the red socket for the variable circuits to have power.

***************************************************
HOWEVER,

3) is there supposed to be any voltage between power posts? i.e.: AB, AC, AD, BC, BD, CD? as I do not detect any voltage in any of these.


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## Kwikster (Feb 22, 2012)

mywong23 said:


> 3) is there supposed to be any voltage between power posts? i.e.: AB, AC, AD, BC, BD, CD? as I do not detect any voltage in any of these.


You should not see voltage on those combinations. The U terminals are the common (ground) and are the only ones to complete a circuit. All the others are voltage outputs.

Carl


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## servoguy (Jul 10, 2010)

You will see voltages between the A B C and D terminals depending on the positions of the controls. Put all the controls in different positions and make your measurements again.

If the circuit breaker is bad (open circuit), and you put a bulb under the red lens, you will get voltage measurements between A B C D and U. However, the current is going through the light bulb, and so if you try to use the transformer to power a train, you will likely burn out the light bulb. I suggest you replace the broken circuit breaker with a 15 amp automatic resetting automotive breaker.


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## mywong23 (Feb 5, 2014)

Kwikster said:


> You should not see voltage on those combinations. The U terminals are the common (ground) and are the only ones to complete a circuit. All the others are voltage outputs.
> 
> Carl


I was told by a Lionel trained tech that there should be a fixed DIRECT voltage measurable between AB, BC, CD, AC, BD, & AD. 
even *when the handles are at an OFF position. *

the VARIABLE voltage circuits are AU, BU, CU, DU. these are variable - as controlled by the 4 handle power positions. 

********************
sidenote: this matches what my LIONEL RW transformer instruction guide says.
the amount of fixed voltage is stamped on the transformer terminal plate.

the tech said that even though the voltages may not be printed on the ZW terminal plate, the fixed voltages have to be present. otherwise something is wrong.....


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## servoguy (Jul 10, 2010)

"I was told by a Lionel trained tech that there should be a fixed DIRECT voltage measurable between AB, BC, CD, AC, BD, & AD."

In a word, the Lionel trained tech doesn't know how ZWs work.


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## servoguy (Jul 10, 2010)

Simple logic to confirm that the voltages between A B C and D are not zero. Set the A lever for 12 volts and the B lever for 8 volts. You should see 4 volts between A and B.


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## gunrunnerjohn (Nov 10, 2010)

I'm glad I'm not the guy that told you about the voltages between the outputs, because whoever he is, he has no idea what he's talking about.


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## mywong23 (Feb 5, 2014)

servoguy said:


> .... I suggest you replace the broken circuit breaker with a 15 amp automatic resetting automotive breaker.


I do plan to replace the existing circuit breaker with a modern version.

unfortunately, that is not the main issue at this time. 
the tech now has his opportunity to actually bench test the ZW.
we'll soon see if his previous statements were true or not.


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## mywong23 (Feb 5, 2014)

gunrunnerjohn said:


> I'm glad I'm not the guy that told you about the voltages between the outputs, because whoever he is, he has no idea what he's talking about.


hey, my inexperienced logic concurs with you guys.

however, I did check my RW instruction guide and tested voltages between posts A, C & D (with the power handle in OFF position).
There is fixed voltages that correspond to what is printed on the terminal plate and instructions....

but then a RW may have been designed and engineered totally different than a ZW-R......

I will post the tech's findings.


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## gunrunnerjohn (Nov 10, 2010)

If you look at a ZW, all four rollers are on the same core. Each roller feeds one of the A, B, C, and D posts. If all the rollers are in the "off" position, there should be no voltage in any combination on those output. Ignore stray capacitance that fools digital meters, connect a light bulb across the output in question and then measure it.

You can measure voltage between the outputs if they're set at different voltages, the voltage you read will be the difference between the settings.

If your tech gets any different result, it's time to get a new tech!


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## servoguy (Jul 10, 2010)

There are no fixed voltage taps on ZWs, Type Vs, Type Zs, or VWs. There are fixed voltage taps on most of the smaller transformers.


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## mywong23 (Feb 5, 2014)

picked up the ZW today 
as we all suspected there are no fixed voltage taps, as Servoguy and my RW confirm, these exist only on smaller transformers.
The tech now also concurs...



servoguy said:


> There are no fixed voltage taps on ZWs, Type Vs, Type Zs, or VWs. There are fixed voltage taps on most of the smaller transformers.


___________________________________

so this ZW-R has 4 variable voltage circuits. however the tech measured *each output to be 27V*. he could not explain why they are higher than usual 20-21V. 
activating the whistle, bumps up voltage additional 4V.

the tech changed the carbon rollers for the two main circuits AU & DU, as the rollers for BU & CU were hardly worn.
he had also changed couple broken terminal posts.

the circuit breaker was left unchanged; as it still functions, even though one of two legs is broken. (I will replace this later)

********************************
to summarize, the ZW-R has been taken apart and put back together. the tech says it works fine, but warns about running full throttle, as the 27V is higher than normal.

looking forward to setting up a small test layout this weekend...

what do you guys think about the 27 volts?


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## servoguy (Jul 10, 2010)

The 27 volts is probably indicative of either very high line voltage or a meter that is out of calibration. Buy yourself a meter at Harbor Freight for $8 and check it again. Check your line voltage also. It should be 120 volts or at least close to 120.

If the output is still 27 volts, better check the wiring inside the transformer, but I know the transformer circuit pretty well, and I don't come up with any way that 27 volts could be correct.


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## servoguy (Jul 10, 2010)

Did you check the BU and CU outputs also?


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## gunrunnerjohn (Nov 10, 2010)

Did you put a load on the circuit you're testing as I mentioned over a week ago?


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## mywong23 (Feb 5, 2014)

gunrunnerjohn said:


> Did you put a load on the circuit you're testing as I mentioned over a week ago?


today is Saturday and just set up a short track loop for the first time.
unfortunately, with any load (e.g. engine or even a lighted caboose by itself), the ZW throws a red light short as soon as power is turned on. 

the same occurs on any of the four circuits: AU, BU, CU or DU.
(no red light short noticed if no cars are on the track)

I disconnected the ZW and hooked up a RW transformer, which ran the train fine 

*****************************

ps: without load, voltage readings using an analog multimeter are closer to specs, than what the tech reported (27V). 

note: the digital multimeter blew a fuse during original testing  
new replacement fuse did NOT restore function - still dead. (fuse has continuity) hence use of analog MM. 
guess I'm having bad case of Murphy's Law....


****************************************
*****************************************

afternoon UPDATE:
talked with tech,
he thinks the circuit breaker is the cause.

I had noticed from the beginning, that one "leg" of the thin, U-shaped piece that holds one of the circuit breaker 
contacts was broken. because the other leg of the U shaped metal was ok, I assumed the circuit breaker would still
function, and I could change the breaker at a later time. I guess I can no longer wait.....

do any of you know if those two .25" round contact points are supposed to be in contact in normal, non-shorted,
situations? I'm now also guessing the U shaped piece might be bi-metallic, to work like thermostat, either keeping those
contact points touching or separating them if a short occurs....

right now, power off, the contact points are NOT touching.

I am learning....

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***************************

further update:
with some testing on my part.

discovered the contact points should be touching at rest. 
as train runs if I keep the contact points touching.
as soon as they separate, the circuit breaks.

tech just called back; saying the ZW-R used an updated circuit breaker than what was used in the ZW....


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## gunrunnerjohn (Nov 10, 2010)

Personally, I just replace the breaker in the PW-ZW with a 10A automotive cartridge type, a much more reliable breaker.


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## M. Mitchell Marmel (May 11, 2018)

gunrunnerjohn said:


> Personally, I just replace the breaker in the PW-ZW with a 10A automotive cartridge type, a much more reliable breaker.


10A, eh? (makes note) Most of the replacements I see on the Bay have 15A, but I'm always willing to be told different, particularly when dealing with little Gomez Addamses at the museum... ;-) 

On the subject of loads, what would you recommend as a good test load? And how long do you keep the load on? I'm going to be doing repairs, maintenance and such on my ZW fleet over the winter...  

Mitch


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## gunrunnerjohn (Nov 10, 2010)

Well, the actual output capability of the PW-ZW is really more like 220 watts, PW transformers are rated at input power. If you're drawing 10 amps from it, it's getting pretty warm and you're pushing it's limits. Add to that a 10A thermal breaker will run for a very long time at a moderate overload, so it's really supplying a peak of 12-13 amps for minutes before it would trip.

At one time I used to rebuild PW transformers, and when testing with a continuous 10A load on a ZW, the transformer got what I'd have to consider uncomfortably warm after 15-20 minutes. The 10A load also drops the output voltage considerably.


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## Norton (Nov 5, 2015)

A fuse might be good option at home but maybe not at a public layout. How many times are there derailments? Once a day or once a month? If its more like once a day then fast breaker would be better. ZWs have a 15 amp breaker because it has a single winding capable of that much current. A 10 amp fuse would presumably be installed in each individual line.

Pete


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## sjm9911 (Dec 20, 2012)

M. Mitchell Marmel said:


> 10A, eh? (makes note) Most of the replacements I see on the Bay have 15A, but I'm always willing to be told different, particularly when dealing with little Gomez Addamses at the museum... ;-)
> 
> On the subject of loads, what would you recommend as a good test load? And how long do you keep the load on? I'm going to be doing repairs, maintenance and such on my ZW fleet over the winter...
> 
> Mitch


I always like this page for transformer repairs. 


Tranz4mrâ€™s ZW Page ï¿¼


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## M. Mitchell Marmel (May 11, 2018)

gunrunnerjohn said:


> when testing with a continuous 10A load on a ZW,


How does one build a 10a load? Keeping it reasonably simple, mind.  

Mitch


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## Millstonemike (Aug 9, 2018)

Three 4.7 Ohm resistors in parallel (~1.56 ohms) will draw ~10 amps at 16 V. The three resistors would dissipate a combined 150 Watts. So you would need a minimum of 50 W resistors.. Here's 100 W resistor source. eBay likely has the similar offerings.

I imagine it might make a difference if the 10 amps is drawn from one ZW output versus spreading it out over three outputs? For testing, you can put the three resistors in parallel on one ZW output or split them up between three outputs.

Having said that, John would have empirical data on the ZW's voltage drop at 10 amps. And the member Tranz4mr has extensive experience rebuilding and testing ZWs. I'd wait to here from him. I asked him to add his wisdom here.


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## Millstonemike (Aug 9, 2018)

mywong23 said:


> picked up the ZW today
> as we all suspected there are no fixed voltage taps, as Servoguy and my RW confirm, these exist only on smaller transformers.
> The tech now also concurs...
> 
> ...


Might first guess would be a short on the primary winding causing it to draw higher current. That would translate to higher voltage on the secondary windings.


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## T-Man (May 16, 2008)

May I suggest upgrading the circuit breaker, and adding the diodes for the whistle. Rollers and cord should be routine.


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## gunrunnerjohn (Nov 10, 2010)

M. Mitchell Marmel said:


> How does one build a 10a load? Keeping it reasonably simple, mind.


Kent is a great resource and does really nice work.


M. Mitchell Marmel said:


> How does one build a 10a load? Keeping it reasonably simple, mind.


I do it the easy way, I have this coil from an oven. I just clip on appropriate places to get the load I need. I usually clip one lead in the middle and then parallel two leads out a ways on either side for the other side of the load, that way I use more of the windings to spread the heat dissipation. As long as I don't let this fall over on the bench, no danger of burning anything. I'm sure I'll never kill this with any transformer I'd ever have to test!


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## M. Mitchell Marmel (May 11, 2018)

Hum! That IS clever, John!


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