How to wire for using two different transformers (ZW and Dual Power O-27)

[Southwest Chief]

I just got a refurbished vintage ZW transformer for our O gauge layout.

For years we've been using an MRC Dual Power O-27 transformer.

Our layout is a simple two track design with a crossover track.  The crossover is insulated so the two tracks are electrically separate.  The crossover is more for looks as we rarely ever use it.  Track is Ross Custom.

Here's a photo overview:

 

With the ZW, our Lionel Railsound Santa Fe F3 (8100 and 8102) locos do not work the best.  The ZW whistle button triggers the bell instead of the whistle.  And then the bell will not shut off again unless you put the train into neutral.  Our other sound loco (a Williams Santa Fe 623) doesn't play either the horn or bell with the ZW.

These "modern" locos work great with the Dual Power O-27 transformer.

However our vintage Lionel locomotives (Pensy 2825 and Santa Fe 623) seem to work a lot better with the ZW.  The 2825 whistle works a lot better with the ZW.

So I was thinking of how to wire it so I could have both transformers available but obviously not both on at the same time.  Perhaps a DPDT toggle switch?

But for some reason I can't comprehend how to do this for two tracks with a single DPDT.  Maybe use two separate DPDT toggles.  One for track one and another for track two?  But then there is no way to prevent both transformers from sending track power to one of the tracks at the same time...although it should not matter since the two tracks are isolated.

As it is now I have only the ZW hooked up (track one to common 1 and A)(track two to common 4 and D).

Does anyone have an idea of how to wire this to use two different transformers but not both at the same time?

[gunrunnerjohn]

FWIW, you can simply swap the leads for the ZW and get the whistle working.  The indications are you have it wired incorrectly, the U terminal goes to the outside tracks.  The only other way that the bell would be triggered by the whistle switch is if someone repaired the ZW with a diode for the disk rectifier and put the diode in backwards.

As far as the switching, you do realize that all you have to do is switch the center "hot" rail, so a DPDT switch should do it just fine.  The outside rails should be common throughout the layout.

[wallyworld]

I seem to recall that the Dual Power transformer had some unique electrical characteristics as far as output that initially created some issues with some manufacturers equipment. re: sound boards. Someone with more of a electrical background could answer if these two very different types are compatible although they can be put into phase. That would be my concern.

http://dfarq.homeip.net/2011/02/using-old-transformers-with-new/

[Texas Pete]

I have a two-transformer layout, and use single pole, double-throw, center off toggle switches to direct either of them to the various blocks. Since the common/return on both transformers are connected I need to direct only the center rail current. The track power of each transformer is connected to one or the other side taps of the switches, and the center tap is connected to the appropriate block. Each block can then be controlled by one or the other of the transformers or switched off. Simple and it works.

Pete

[lionelsoni]

Amen to what Pete posted.  Notice that, doing it that way, you can have as many blocks as you need or want for only a toggle switch per block.  The scheme he described, which is what I use too, allows you to cross from one loop to the other without the risky maneuver of changing from one transformer output to another, which is particularly unsafe if done between two outputs of the ZW.

But you now have two transformers, each able to run (at least) two trains.  Here is a simple way to have the kind of block control that Pete and I recommend--and to be be able to select between the two transformers as well:  Wire it the layout as already described, but don't connet the two groups of switch terminals directly to either transformer.  Instead, connect each group to the common terminal of another SPDT switch.  Then wire the outer terminals of each switch to one of the outputs from each transformer.  For example, one of these two switches might select the A output of the ZW or the A output (or whatever it's called) of the other transformer.  The other switch might select the D output of the ZW and the other output of the other transformer.

This way you can have two groups of blocks, one group powered from one source and the other group powered from another source.  Each source in turn can be selected to be from the ZW or from the other transformer.  And actually there can be a third group of blocks whose power is shut off, by using the center-off position of the block switches.

[Penny Trains]

Great layout!    I love Plasticville! 

On my bedroom layout I use a DPDT Leviton knife switch to alternate between AC and DC transformers.  It's only a small O31 oval so no blocks are neccessary but it works flawlessly.

Becky

[Southwest Chief]

Thanks for the information.  Explained exactly what I need to do.

A lot easier then I was making it.

 

Oh and the ZW must have a flipped diode since I had the wiring the other way and the bell still activated on the Railsounds equipped F3.

[gunrunnerjohn]

If wired either way activates the bell, I don't know what's wrong, that's mighty odd! :D

If you use a DC voltmeter on the ZW and actuate the bell with the positive lead on the variable output and the negative lead on the U terminal, do you get a positive or negative reading?  It should be negative for proper operation of the whistle.

 

[lionelsoni]

It's the other way around, John--positive on the center rail for the whistle.  The old Lionel schematics all show the diode backwards.

[gunrunnerjohn]

Duh!  I went over and measured it, you're right.  Why did I think it was negative?

[Southwest Chief]

I thought it was weird that the bell only played.

I just flipped the wires and now the horn plays. 

So strange.  Only thing I could think of when testing is that I thought I flipped the wires but in actuallity put them back just like they were

So now the center rail is to the A port while the outer rail is to the first common port.

[lionelsoni]

Those common ("U") terminals are all connected together right inside the case, which is why they are the one(s) to connect to the outside rails of the entire layout (apart from getting the whistle and bell right).

[Southwest Chief]

Wanted to update this.

I used two knife switches.  One for each track.

So I can either run both tracks on the ZW.  Both on the MRC.  Or one on the ZW and one on the MRC.  Pretty flexible system.

Useful when I have a loco with bell sounds that won't trigger using the old ZW but will with the MRC.  And useful when running old classics like our 2525, 623, and 2343, which seem to all run better on the ZW.

[lionelsoni]

It also looks from the picture like your wire is seriously undersized.  The ZW's circuit breaker trips at 15 amperes, which calls for 14 AWG wire, not that the breaker will ever trip if you get the voltages mismatched between the two loops.  So, with that arrangement, it's not safe to use the crossover, at least with the ZW.