Models that turn in to kits

Not a complaint... but a repair story.
I picked up a N scale Kato GP50 at a show today, and ran it around a bit on the layout. Noticing it ran rather fast at low voltages and wanting
to confirm there was no decoder inside, I opened the case to take a look. There was a pretty nice drive mechanism, with a circuit board on top for the lights and transfering power.
After putting it on the track to watch how it ran, the locomotive wouldn't move. A couple nudges, and still no movement. Since it's not a bad section of track, I grab the multimeter and check for shorts. Yep, shorted.
So, I start taking the model apart to find the short... I take a screw out on top and the truck falls off, taking a bearing with it. In my attempt to isolate the circuit board, I remove the four screws holding everything together. At this point, my locomotive is now in kit form.
In this form, I've got an idea of how power is transfered to the motor. On the top of the motor, there's a brass conductor that connects to the circuit board. The tricky part is the how the other side gets its power. There's a silver (aluminium?) "box" that attaches to the circuit board, and transfers its power to a brass terminal at the bottom of the motor.
This box passes extremely close to the brass conductor at the top of the motor, and I suspect when I took the shell off to get a look inside the brass conductor contacted the box and caused the short.
This is actually the second time a model's turned in to a kit for me, the first one was a building that had the glue fail due to the high humidity.
Puckdropper
--
Wise is the man who attempts to answer his question before asking it.

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--

Where was the show, Puckdropper?

Frank Rosenbaum
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Illinois Central College in Washington, Illinois. There will be another show there in February, probably the 17th.
Puckdropper
Postscript: Please make sure your message is above the "-- " in your messages. My newsreader cuts off signatures (as per Usenet etiquite) and everything below "-- " is considered the signature.
--
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Puckdropper wrote:

well, then - since you probably haven't seen my sig - which might contain something of interest - I'll eliminate the sig flag (this one time only) so you can visit if you care to...
randy guttery
A Tender Tale - a page dedicated to those Ships and Crews so vital to the United States Silent Service: http://tendertale.com
http://www.glimpsesofmeridian.com Trains, planes, steam and stuff...
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Let me rephrase that so it's clear: Upon posting replies, my newsreader trims the signature. It's considered good Usenet etiquite because of those fellows with 20+ line .sig files. When displaying a message, it displays the signature.

Puckdropper
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Puckdropper wrote:

Sorry. I'll pay more attention next time.
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
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So did you manage to put it back together or is it still in a form of a kit?
IIRC, Kato N GP50 has a similar construction to the GP38-2. While revolutionary for its time it is also a pain in the a$$ to assemble.
The 4 long screws thread into the power pickup and truck retaining plates. There are also plastic insulating "pipes" in 2 of the screw holes through the chassis. Those screws also attach the motor supply straps. One is a brass strip on one side and the other one is that aluminum shield you've mentioned. That shield should be slightly elevated over the circuit board. It should have a Z-bend in its screw tab. There is a brass strip on the bottom of the motor which pokes out through the side of the loco. That strip should be tucked under the aluminum shield and that connect the bottom motor tab through the Al shield to the top circuit board and screw.
Those locos are geared pretty high so they run fast.
Also the circuit board is not a decoder. It only holds the LEDs and resistors for the headlights. Unless it has a custom-made DCC decoder (as I never seen a drop-in DCC decoder board for this loco).
Did the loco come with its original box? If yes then there should be an exploded diagram of the loco on the bottom of the box. That should help out in reassembly.
Peteski
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wrote:

It's back together again, and works again.

Thanks for the information. Everything was as you said.

Actually, they're diodes. With standard bulbs, all they're there for is directional lighting.

The exploded parts diagram was a huge help in reassembling the locomotive.

Puckdropper
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snipped-for-privacy@my-deja.com says...

I may have missed my explanation of the motor contacts in my post, but the pic should make that clear. I have an original parts sheet if that would be any help for anyone.
fl@liner
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snipped-for-privacy@yahoo.com says...

Pay attention to the sleeves that insulate the left side screws from the frame. Also, the motor shield thingie should be away from the contact strip for the upper brush. And...insure that the contact strip doesn't touch anything when the shell is reinstalled. Pic:
http://inlinethumb38.webshots.com/29157/2221819550100678541S600x600Q85.jpg
fl@liner
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snipped-for-privacy@afu.com (fl@liner) wrote in
I took a few extra precautions when assembling the Faraday cage (I believe that's the purpose of the aluminium shell) assembly. The top of the circuit board (except for the screw holes, of course) and the side nearest the shield have been covered with electrical tape. That way, if that tab gets moved it hits insultation.
Puckdropper
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On 19 Nov 2007 18:20:14 GMT, Puckdropper

This tagline has been certified to contain no political rants.
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Thanks for the information. If I decide to install a decoder (only if I upgrade to DCC), I'll do a couple experiments to see if there's any interference. If not, I might just run a wire from the bottom tab.
Puckdropper
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in

Like you already noticed, Kato dropped the shield in all their newer locos. I think it was there for heat reasons rather than for EMI shielding. I also forgot that they used bulbs and diodes on those locos. You're correct of course. Those locos are now around 20 years old!
Peteski
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