# Basic DC power supply from vintage Lionel Z/ZW/KW



## JPCaputo (Jul 26, 2009)

Out of not wanting to spend $150+ for an MRC G 10 amp pack. I made a box to mount on the back of a 190 watt KW with direction switches and breakers. It puts out about 8 amps at 0-18 volts DC.

Total investment, about $30 over the price of the KW.


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## Dan Pierce (Jan 2, 2008)

Depending on what you run, 18 volts is on the low side and if unregulated it could drop with load to even less voltage.
Most steam engines will be OK, but modern diesel/electric need more for 'high speed' operation. Of course if you do not need high speed then this does not matter.


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## Cataptrra (Mar 16, 2015)

If your loco's have sound cards installed, that 18 V IS NOT going to be enough to keep the battery charged that keeps the sound going at low speeds. 

You really do need a power pack that handle much more, if you operate smoke units, lighted passenger cars, additional sound cars or sound installed in the loco, lighting{especially diesels that usually have more lights than a steam loco}, multiple loco lash-ups, or any track side accessories that you might run off the rails, you're going to find that 18 V power will fall really short of your expectations.

*EDIT: "One thing I forgot to mention and this is very important. If the power isn't suited enough to the loco, it may run, but being underpowered can cause the loco motor{s} to overheat, which can also cause your power supply to overheat, and if you don't have any safeguards in place to "shut the power down" under thermal breakdown, this could be disastrous, as your power supply could literally go up in flames and smoke. So make sure your homemade supply has some type of fast acting fuse{s} in line with the rails as well as the ~AC~ feed to it. This will kill the power to everything and hopefully prevent any meltdown or fires."*

Believe me, it's better to invest in a quality, high amperage, higher voltage output{ at least up to 30-35 VDC output and 10 Amps} power pack than one with less power that may end up being a huge disappointment because it can't carry the load you're putting on it.

If running single loco's, unlit cars and no sounds, you may be fine with your home-brewed system, but if you want to run multiple loco's, use the smoke units and have sound, you're going to need something with more amperage and voltage to get the job done. 

Believe me, I know, been there and done this too when I first started
. 
Now I use an old AristoCraft 10 AMP 35 VDC power pack and wireless TE system and it's served me very well for many years {bought new in 1997, same year I started, but after trying to use lower amperage/voltage power systems that just could not cut it}, only thing I've ever replaced is the TE Transmitter and that was very recently and thanks to a member here was able to get a used replacement TE for mine that went out this year in 2016..


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## toddalin (Jan 4, 2008)

You don't need more than 24 volts in this scale and are going to fry lots of equipment if you put 30+ volts to it. (Some stuff may even fry at 24 volts _to the circuit_.)

Also, more "available" voltage doesn't make the sound card recharge any faster/better. The sound cards have an internal regulator and after about 8-9 volts to the rails, the internal circuitry regulates the battery charging voltage regardless of if you put 10 or 22 volts to the rails.

If you are only running your trains at 15 volts, it makes no difference if you have 24 volts or 36 volts "on tap," unless of course you accidently turn it up to 30+ volts and burn out the sound card, which wouldn't happen with 24 volts on tap.


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## Dan Pierce (Jan 2, 2008)

Power pack voltage needs to be higher than what you supply to a controller.

Case in point is the new Zimo system which requires a 30 volt DC supply in order for the command station to supply 24 volts to the rails.

As always, read manufacturers specs.

And as far as sound units go, 18 volts is plenty for all my sound units when I run analog/DC (LGB, Phoenix, Sierra, Zimo). And indoors I do not go as high as 18 volts on the track as I have 4 foot diameter curves.


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## Cataptrra (Mar 16, 2015)

Just know the AristoCraft Ultima Power pack I have is rated 35VDC output with 10AMPS, I use the TE on PWC, I have yet to burn out or destroy anything with it.

As for my sound cards, they are older PSS '97 sound cards. I these have installed in loco's and sound cars, the voltage on the rails DOES, in fact, have a bearing on the recharging of the battery. It states it right in the manual for the sound card which voltage to use and at what time to use it. if I run the trains at a slow voltage level, battery will discharge and NOT recharge until I have at least 12VDC-15VDC on the rails, otherwise sounds will become erratic or not play at all.

So I have to disagree with voltages and recharging of batteries not being an issue, maybe with the newest sound systems, this issue might not exist, but if you use older units{like mine}, could be a very big difference in how they are set up, so voltage could very well mean the difference between a dead battery or one being recharged, along with sound or no sound.


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## toddalin (Jan 4, 2008)

Cataptrra said:


> Just know the AristoCraft Ultima Power pack I have is rated 35VDC output with 10AMPS, I use the TE on PWC, I have yet to burn out or destroy anything with it.


I would suggest that you check your voltmeter.

I have a Crest Ultima sitting on the shelf and just measured 25.65 volts output with no load. This is actually a couple volts more than the older AristoCraft Ultima puts out (which I also had).

As for the Sierra sound card, I convert these to supercaps and am very careful about how much voltage is fed to the battery and at what voltage it starts to feed. Again, check your meter.


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## Dan Pierce (Jan 2, 2008)

My ultimas do not go over 25 volts and with a load will drop to less than 16 volts.
One had the old style rectifier go bad and I replaced it with modern diodes, less voltage drop with a load. The only way to get 35 volts out of these is to rewire the transformer ( it is enter tapped and only used 2 diodes).


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## Cataptrra (Mar 16, 2015)

When I first got my 2 Ultima Power Packs and tested them with a voltmeter, I did get 35VDC on their output connector. 

I haven't tested them lately, I'll have to get out my digital multimeter and see what they're putting out now that they've been used very heavily and see what they show now.

I just took it that the voltage would remain constant from the time they were new until they finally went out to pasture.

Will have to check and let you know what mine are putting out now.


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## Greg Elmassian (Jan 3, 2008)

The Ultima is an unregulated power supply, a transformer, a rectifier, and I believe a small filter cap.

I have never seen a transformer increase in output over time, just less.

Greg


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## Cataptrra (Mar 16, 2015)

Just tested them, one puts out 22.18 VDC, the other puts out 25.12 VDC. For an unregulated power supply, they seem to hold steady on their readings. 

Most unregulated power supplies I've tested always seemed to fluctuate between 1-3 Volts continuously,

So I thought these were regulated since there was no fluctuation in current reading, but seeing I've never opened one up to peek inside at the internal electronics/components that make it up, I can't say for certain.


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## Dan Pierce (Jan 2, 2008)

The Ultima output voltage will drop as current draw is increased as there is no regulation. The big capacitor is there to filter out ripple and ripple will increase as current increases which will give a lower average DC reading. Not a bad thing, it is just how it works.

Great power source for 4 foot diameter layouts, I have 2 in use indoors and a DPDT switch to select this unit with the 27mhz TE or DCC.


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## JPCaputo (Jul 26, 2009)

That's a lot of good information. I am just running basic engines, straight analog control. Smoke and lights as well.

If I as running Dcc or a PWM controller like the crest or similar, I would get a meanwell switching supply and set it proper.

That old 275 watt ZW with the DC adapter is able to run my Bachman Connie, with smoke, lights and several cars around a loop without problem. 

I am not looking for flat out speed, I'm usually running fairly slow to begin with. 


I might change the internals of the rectifier a b


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