I've got a set of MTH HO scale Norfolk and Western passenger cars that have "flicker-free lighting". They have been flicker free for several years now, taking up to five minutes or so for the lights to go out after killing the power to the track. Now I notice one of the cars flickers as it rolls over turnouts, and the light goes out immediately when I turn off the power. If I remember correctly, there's two capacitors on the circuit board on these things (I could be wrong). Is it likely the cap just went bad? Or more likely to be a solder joint? Can you test a capacitor with just a cheap Radio Shack analog multi meter?
Mike C.
Look carefully at the capacitor. It should have a flat top (depending on the kind of capacitor of course) If the top is buldged it needs to be replaced.
I have had good luck replacing bad caps on the older style flourscent flat screen monitors. The caps are in the lighting circuit not the data circuit. Separate board entirely. Newer LED screens do not have these caps.
I have some dead motherboards with buldged caps, but I did not try to replace those, real motherboards are a lot mor fiddley than simple lighting ballasts.
Of course I have seen other caps fail... sounds like a firecracker or maybe an ashcan when they go off. You will need to change your pants after that.
ROAR
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wobblinwheel Is it likely the cap just went bad? Or more likely to be a solder joint?
Is it likely the cap just went bad? Or more likely to be a solder joint?
My vote is for a bad wire connection. Which might be a solder joint. Or it might be one of those little press-on plastic thingys that we see on DCC decoders.
But, as Lion points out, a visual inspection of the item should also include the capacitors. Ugliness is definitely a cause for further thought.
Can you test a capacitor with just a cheap Radio Shack analog multi meter?
Sure. Apply a charging voltage long enough for it to charge. Wait "five minutes", and put the meter probes on it. It should read close to the charging voltage. And "slowly" go down as the cap drains through your meter. "Slowly" is in quotes, based on meter resistance.
Ed
Capacitors certainly can fail. Lion covered it pretty well. If there's any sign of gunk leaking out, or the case is bulged - it's shot. The gunk that leaks out WILL eat through circuit board traces so it must be cleaned up when replacing the capacitor.
The explosive failure usually only occurs if you overvolt the cap (put say 30 volts through a 16 volt capacitor) or hook up a polarized capacitor backwards. Load of fun if done in controlled circumstances, not so much fun if it happens inside a finely detailed model.
--Randy
Modeling the Reading Railroad in the 1950's
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If any device on the printed circuit board that has a wire going through the circuit board, the solder around it should be shiny. If the solder has turned gray where it touches the wire, that is probably a loose connection. Easy fix. Just touch a hot soldering iron to the wire for just a few seconds. That should liquefy the solder and repair the connection.
wobblinwheel I've got a set of MTH HO scale Norfolk and Western passenger cars that have "flicker-free lighting". They have been flicker free for several years now, taking up to five minutes or so for the lights to go out after killing the power to the track. Now I notice one of the cars flickers as it rolls over turnouts, and the light goes out immediately when I turn off the power. If I remember correctly, there's two capacitors on the circuit board on these things (I could be wrong). Is it likely the cap just went bad? Or more likely to be a solder joint? Can you test a capacitor with just a cheap Radio Shack analog multi meter?
Those caps sound like keep alive but not sure without a photo.
Sounds like a defective connection. The keep alive is not doing it's job.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
I endorse what Randy and Lion said.Most cheap caps use a liquid paste as the dielectric, and these have a tendnecy to dry up or leak out over time. When they fail, it causes the caps to blow up, or bulge, or leak around the edges. (This does not apply to the really small caps which look like two legs off a round package the size of a dime/quarter. Those are aluminum based)Solid caps are the best. But they are pricey.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
Capacitors can go bad for sure. I remember in the 1960's when they sold car radio filter kits to filter out the ignition noise from the radio, it was nothing but a huge capacitor circuit. I saw many of the them swollen up and cracked as an auto mechanic because they were installed wrong.