Help in indentifying an old HO engine...

Randy or Sherry Guttery wrote:


The ordinary PC power supplies need a solid load on their logic power (5 or 3.3Volt) in order to stabilize the regulator. With no load on the logic power all sorts of bad things happen.
David Starr
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David Starr wrote:

What would e an effective "...solid losd..."?
Incandescent bulb of appropriate voltage? Resistor just disappating heat?
I'm looking to use some older PC PSes to provide power for slow motion switch machines from the 12 v. leads.
Thanks.
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jJim McLaughlin wrote:

yeah, you have the idea - some current to keep the output filters bled off so the regulating circuit can keep control. Without sufficient "load" the supply could drift slightly high - the regulator - in trying to bring it down - would come close to completely shutting down - and when a load would hit - it would take a bit for the regulator to react...
Lab quality supplies often use "active sinks" - i.e. pass elements to a minus supply to "suck down" the filters really fast when needed. Most lab supplies I'm familiar with are rated to "sink" roughly 10% of the current they are designed to supply.
Back to your question - use a resistive load that consumes enough current so that your powered device doesn't overload the supply while working - yet enough load so the supply is stable when the switched load is cycled off and on... A little trial and "tweak" can determine good enough values...
best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
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Randy or Sherry Guttery wrote:

Thank you!
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jJim McLaughlin wrote:

I'd go for 1 amp or more on a PC supply. That's maybe 50 LEDs, or 15 6-volt incandescent lamps, or a 5 ohm resistor. The 5 ohm resister will get hot, 'cause 1 amp times 5 volts is 5 watts. I'd go for a 10 watt or larger resistor to keep the heat down.
David Starr
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David Starr wrote:

Yes, which is why I installed load resistors permanently across all three supplies... "bleeder current" is about 5% of rated load... *usually* that's enough to keep it happy... obviously with a seriously inductive load - it wasn't happy and all. IIRC it came out of a large hard disk cabinet - which is why the +12V is so "beefy"...
best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
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Looks like a good test well run. 0.6A is right in the ball park.
As somebody pointed out, wheels slipping is full load and is above the load you'd normally run at. Temperature rise is the usual metric used in specifying the load rating. Total temperature counts when your defining the limits.
Try the test with the engine blocked on a piece of track.
--
Fred Lotte
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Yes, I forgot about that problem. If you take the motor apart, you should 'short out' the magnet with a piece of iron to minimize the loss of magnetism. As David points out, 1 amp is high.

Another way to count the turns is to cut the coil and count the pieces. I've heard of this being done on much larger motors with 'random' windings.
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Fred Lotte
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On 11/18/2007 7:06 AM David Starr spake thus:

With all due respect, I seriously doubt that. The reason is that I had my own motor-rebuilding experience yesterday: helped a friend fix his kitchen exhaust fan.
When I pulled this unit out, it was *completely* covered in very thick, very sticky kitchen grease. Had to wipe it off with turpentine just to find the damn mounting bolts for the motor.
Long story somewhat short: while the insulation on the supply cord was completely gone and had to be replaced, basically dissolved in the grease (soldered new cord on and used heat-shrink tubing to insulate it), when we pulled out the field coil, it was completely intact. We're guessing this motor dates back to the '40s or '50s; after cleaning and reassembling, it runs as well as a brand-new one.
The field coils were completely intact. So if a motor in a grease-filled airstream can survive that long without the windings deteriorating, I reckon an HO locomotive stored in a box somewhere is going to suffer no such decay.
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message

the grease

plastic
free-run
way too

4-5amps is very high for that type of motor. It may someone in the past lubed it with the old Lionel parafin based grease. The problem with that stuff is over the years, if the gears aren't used regularly, it hardens up and essentially turns into candle wax. If you push the throttle up in an attempt to get the motor to move the gears through that stuff, you can pull enough current to burn out the windings.
Clean the old stuff out completely and try some Lubriplate (if you can find it) or Labelle 106 grease. If the current draw doesn't go way down, there's probably already damage to the windings.
Len
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Athearn used to market two different drive systems for their diesels back in the 1950s; the cheap ones with the "rubber band" drive, and a more expensive geared system as well. This looks to me like the more expensive of the two systems, but I can't be sure because I couldn't afford the "good ones" back then!
Pete
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On Fri, 16 Nov 2007 17:10:00 -0600, Randy or Sherry Guttery
I was looking through my old MR's today and I found this in the Jan 1994 60th Aniversary Issue. They asked their readers what was the most profound change in the hobby over those 60 years. One reader reponded:
"Athearn's introduction of the HO scale diesel in 1954 (under the Globe name), in my opinion, changed the industry overnight in three ways. First, it forever legitimized the use of styrene plastic for locomotives. The detail of the engine exceeded everything else at the time, incluing metal castings. Second, its low cost but high appeal probably introduced thousands of budget-minded people to the hobby. Third, many a die-hard steam modeler probably found a sudden need for diesels on their pikes with this model! More amazing is the fact that the Athearn F7 will have been in production for 40 years in 1994 and is still a great-looking, low-cost, popular model. Happy Birthday Model Railroader and Athearn F7." L. Ivan Potoski, Henderson, NV.
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