Fixing the 977 Caboose Flagman Buzz - Model Train Forum - the complete model train resource
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Old 08-05-2019, 11:54 PM   #1
Sagas
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Join Date: Dec 2013
Location: Warsaw, ON.
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Fixing the 977 Caboose Flagman Buzz

Below is an article outlining how to quiet the caboose in answer to Cramdens' question in "Photo of the Day". J.B.

"Does your 977 caboose 'buzz'? Well this is normal, but if you want to eliminate that 'buzz' here is a solution submitted by Alex Mendelsohn. (Paul)

Start by carefully removing Mr. Rubber with a small pair of pliers. Gentle lifting will separate the lil guy from the swing arm. Set him aside.

The "rivets" on the 977 caboose are splined pins. They're easily removed by rapidly heating them with a soldering iron. I used a well tinned chisel-point soldering iron of about 75 W capacity.
If you keep the tip scrupulously clean by frequently wiping it on a wet sponge, it won't mark the splined pins with any solder. I simply heated the pins for about ten seconds each, and pulled each one straight out with a pair of needle nose pliers. Easy!

Next I placed the caboose on the bench with the solenoid assembly to my right. I then snipped the wire that leads from the uninsulated truck; I cut it about 1/4-inch back from where it's staked to the solenoid coil. That way, there's no strain on the coil termination itself.

By the way, Gilbert expertly left a tiny "service loop" at the truck. That's a nice touch which gives the stranded wire an extra measure of flexibility as the truck swivels. Don't pull the wire too tight and crimp that little loop.

I left the original lamp wiring in place and clipped the wire leading from the insulated truck (opposite end of caboose) where it terminated on the solenoid. This left the solenoid isolated; the original wiring has one end of the solenoid connected to the uninsulated truck.

Next I installed a "block"-style full wave bridge rectifier next to the lamp, using a small piece of double-sided tape to hold it in place.

The rectifier I had in my junkbox was rated at a hefty 15 Amps. It was originally intended for use in a power supply for a 100 W stereo amplifier! It measures about 1.25 inches square and perhaps 3/4 of an inch high--including the terminals. Overkill, but who cares?

You could substitute four discrete 1 Amp diodes (such as 1N4001 or 1N4002 types) for the preassembled bridge (I described this in my notes for the reversing handcar). But, if you purchase an insulated bridge, as mine was, so much the better. By the way, some bridge rectifier assemblies have a metal base. If you get one of those, take care to insulate it from the circuitry inside the caboose.

Now, solder the lead from the insulated truck to the "AC" input terminal (either terminal will do) on the bridge. These terminals are sometimes marked with a little squiggly sine wave symbol; sometimes they're marked "AC". Solder the stranded wire from the uninsulated truck to the other "AC" input on the rectifier block.

Then wire the (+) and (-) outputs from the bridge to the solenoid. Polarity doesn't matter.

That's all there is to it. Reassemble the caboose. It's not hard to do. I found that the splined pins simply press-fit back into place without the need for any adhesive or heat.

Put the flagman back on and press him into place. Place the caboose on the track and apply the throttle. You'll find that the flagman is now stable and quiet! However, there is a caveat.

You MUST now run your caboose on AC!

It will not work on DC trackage.

By the way, I initially tried using a simple single diode half wave rectifier and a 100-microfarad electrolytic filter capacitor, but the solenoid didn't like half wave DC. It chattered. The bridge is the way to go."
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File Type: jpg Fix For Flagman Jitters.jpg (40.1 KB, 53 views)
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Old 08-06-2019, 12:21 AM   #2
shaker281
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Join Date: Jun 2019
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Awesome! Thank you for this. Not sure that the dis-assemby of my 979 is the same, but this is a (big) step in the right direction.
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Old 08-06-2019, 08:54 PM   #3
cramden
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Thanks Sagas for finding the article. I couldn't remember where I saw it ,but knew I had read it.
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Old 08-07-2019, 06:24 AM   #4
shaker281
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Quote:
Originally Posted by cramden View Post
Thanks Sagas for finding the article. I couldn't remember where I saw it ,but knew I had read it.
I never doubted you. And what AmFlyer said about it probably being a diode bridge made perfect sense too.
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Old 08-07-2019, 07:07 AM   #5
mopac
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I saved the article and will get to it someday.
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Old 08-11-2019, 11:20 PM   #6
goldinhands
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Join Date: Mar 2016
Location: Chicago Suburbs
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Scales Modeled: "S" Gauge
You can by bridge rectifier's from a good electronic supply house like Mouser or Digikey and then you won't need individual diodes. I like to use the square type and as Sagas said then you can tape them in place with double sided tape.
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