US Hobbies GP-7

[ScaleCraft]

usually low voltage bulbs are wired in series with the motor, with dropping diodes.....your schematic doesn't make sense.

[R.K. Maroon]

My theory is that it is a novel method of getting constant-brightness headlights. The power distribution system had an AC voltage on it at all times. The inductance of the DC motors would block most if it, but the AC capacitors would pass it. The switch is indeed just to reverse the direction of travel. The operator had some reason to keep the polarity of the rails fixed -- perhaps to support a signalling system. It's not likely anybody would do anything like this today, but there were all sorts of ingenious systems back in the early days, as a perusal of old Model Railroaders will indicate.

No proof -- just a theory
Jim

[ScaleCraft]

I re-iterate. The drawing makes no sense.

I did mention the possibility of originally being AC, but since the motor shown in the schematic and the photo is permag, no AC input UNLESS there is abridge and filters, none of which exist. Well, caps but wired for lights.
AC power to field wound motor would have had no effect with the switch as wired. Either armature or field need to be fixed to rails, then reverse the other.

So, was this originally AC track power, now DC motored? Or was there a bridge on the shelf we have no idea what was for?

[ScaleCraft]

went all the way back to the beginning of this thread, saw a photo of an original chassis that looks like the current chassis under discussion, and the comment that your chassis is production and not scratched.

Motors are the same, which eliminates the idea that this engine was AC powered, field wound motor. Could have still been AC powered I suppose, with bridge rectifiers and all, but why.

And if at some point the rectifier was removed and loco rewired, set up to run on straight DC, then why leave the lighting the way it is?

I mean for constant lighting, three diodes (paralleled) would give you .75V per device, and 2.25V total to wire your 222 bulb across, but the lights are not apparently wired that way.

Stranger still.

[ScaleCraft]

So you are thinking a low power high frequency AC component on top of the DC supply to pass through the caps and light the bulbs.

Interesting theory, and I can't imagine the fiddling to come up with that supply and load.
Possible.

And probably a bunch of locos so equipped by original builder.

When it would have been so simple to use six diodes in each motor leg, two sets of three opposing, 2.25V bulb across them. Lights on before the motor started turning.

Of course, the upside to that design in this loco is lights would have all been on when the HF supply was on.

Still cannot imagine.

Too bad Barry is gone, he could have added that to his handbook on DCS.

[webenda]

My theory is that it is a novel method of getting constant-brightness headlights. The power distribution system had an AC voltage on it at all times. The inductance of the DC motors would block most if it, but the AC capacitors would pass it. The switch is indeed just to reverse the direction of travel. The operator had some reason to keep the polarity of the rails fixed -- perhaps to support a signalling system. It's not likely anybody would do anything like this today, but there were all sorts of ingenious systems back in the early days, as a perusal of old Model Railroaders will indicate.

No proof -- just a theory
Jim

The circuit makes perfect sense Maroon. HF Constant lighting was common when I was into HO. There was even a commercial HF Lighting unit available. As for a DIY circuit, here is one (the output capacitor keeps track DC voltage out of the HF Lighting output transformer just as the capacitors in the locomotive lighting circuit keep track voltage off of the lamps, as you said.)



Diodes don't work for lighting when there is no power to the track. HF Lighting solves that problem.

When DCC appeared, HF Lighting disappeared, the technology was forgotten, waiting for newbies to discover it in old model trains and puzzle over it.

[R.K. Maroon]

Thanks, Wayne -- That's really cool. It would be fun to breadboard it up and give it a try, but I should have done it before I ripped the circuit out of the two locomotives.

DId you find that circuit somewhere or did you gin it up yourself?

Jim

[ScaleCraft]

I did note that the circuits shown do not allow for directional lighting. Seems a backwards step unless you are used to Lionel with e-units with non-directional lighting (factory) and full lights in neutral, power on.
Of course the OS3rd adds to that.

[webenda]

Thanks, Wayne -- That's really cool. It would be fun to breadboard it up and give it a try, but I should have done it before I ripped the circuit out of the two locomotives.

DId you find that circuit somewhere or did you gin it up yourself?

Jim

Yes is the answer to both questions. The individual sections of the HF Lighting supply can be found in many books, on data sheets for the 555 and transistors and in Forrest Mims III's many publications.

Forest Mims III: http://www.forrestmims.org/
The 555 oscillator can be found here: https://en.wikipedia.org/wiki/555_timer_IC
The darlington pair amplifier can be found here: https://www.electronics-notes.com/artic ... n-pair.php
The transformer is found here: http://www.tslrr.com/hifreq.htm

Wayne Roderick wound his transformer for 8 volts output (rms? Peak? Trail and error for bulb brightness?). He also added feedback for voltage control. Voltage control seems like overkill for this application [opinion.]

[webenda]

I did note that the circuits shown do not allow for directional lighting. Seems a backwards step unless you are used to Lionel with e-units with non-directional lighting (factory) and full lights in neutral, power on.
Of course the OS3rd adds to that.

Yeah! Whoever installed the lighting circuit failed to include a switch to turn off whichever light was rear (short hood forward or long hood forward.)

[ScaleCraft]

Ah, but they added a polarity switch. One would have thought another switch on the other side would do it, especially in the "day" without dcc and all that. Heck, I use switches still for smoke (if the morons...err...customers want it), volume, and one even for simple/compound on articulated Mallet chuff.