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Old 14th November 2007, 07:45 PM   #1
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Default Model train throttles?

I was just reading through one of my model train mags, and it made an offhand reference to how 50's era DC model train regulated throttles were made with tubes, whereas of course now solid state analog and digital controls dominate. It had actually never occurred to me before that this would be the case, since trains run on low voltage DC.

I think such a throttle would be the cat's meow for the layout I am planning to build. Do any of you old hands have any schematics in your old files, or know of where to find them?
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Old 14th November 2007, 09:11 PM   #2
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What if you had quite narrow (and frequent) pulses of 100V DC applied to a 12V motor? I'll bet the motors would be very responsive.
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Old 14th November 2007, 09:26 PM   #3
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Yes; nice tease. And?
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Old 14th November 2007, 10:10 PM   #4
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When I was young I inherited my grandfathers huge train collection. I had several train controllers that varied in age from old (probably late 1930's) to new (late 1950's). They all were essentially low voltage variacs. The output was AC and went from zero to about 18 volts. Even at a young age I used a monster Lionel train transformer to "test" things.

The Tektronix model 504 scope had a switching power supply that used a 6DQ6 for the switch element. I haven't seen the schematic in years (like 20 years).
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Old 14th November 2007, 11:33 PM   #5
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Quote:
Originally posted by tubelab.com
I had several train controllers that varied in age from old (probably late 1930's) to new (late 1950's). They all were essentially low voltage variacs. The output was AC and went from zero to about 18 volts. Even at a young age I used a monster Lionel train transformer to "test" things.
Yup, tubelab is correct about the variac controllers. I too inherited a Lionel train set as a kid (worth many, many $$$ today) and used the variable controller to experiment. Every year after taking the train set of out storage, I would carefully clean the tracks and sand the contacts clean so the locomotive would get enough juice to make it all the way around the track.

Don't ask me how, but more than once I put my tongue across the "hot" rails !!!

Thus, I became an engineer...

-- josť k.
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Old 15th November 2007, 01:19 AM   #6
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Is it a mere coincidence that Jose and I are both engineers at the same facility? My introduction to electronics came when the scissors met the wall outlet. The sparks were too cool. The glowing hairpins on the train tracks came later.
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Old 15th November 2007, 01:24 AM   #7
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Quote:
Originally posted by korneluk

Don't ask me how, but more than once I put my tongue across the "hot" rails !!!

Thus, I became an engineer...

-- josť k.

Hehehe, I once had the marvellous idea to put the wires of the 14VAC outlet of my train transformer in my mouth.. The worst electric shock I ever had, and I've had quite a few since..
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Old 15th November 2007, 01:25 AM   #8
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Quote:
The glowing hairpins on the train tracks came later.
Ahhh...childhood

Ya know,I still have a train set out in the shed.. Hmm.
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Old 15th November 2007, 01:43 AM   #9
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Here's the PS snippet from a Tek 504.

This is starting to look hard. How about just a tube rectifier feeding some VR tubes in parallel, with a pot to shunt voltage? Can they be paralleled safely?
Attached Images
File Type: jpg tek 504 ps.jpg (63.0 KB, 290 views)
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Old 15th November 2007, 02:16 AM   #10
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In my ignorance, I would imagine that the important thing is the current feeding the locomotive. The tracks and wheels make intermittent, generally not very good contact, so I would think that voltage regulation is not very much use. A variable CCS supply might work best, maybe? Doesn't sound like a very good application for tubes, though.
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