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Model Forum / General / Railroads / November 2005Wheel wipers redux; tape player motors ; KF transformers
Dear folks: Well, I asked a question about wheel wipers and got a lot of answers, so I went to inspect one of the worst electrical offenders on the roster, my repowered Life-Like Teakettle. When I did so, I realized that the wheel-back wipers were mostly hitting the plastic centers. I reshaped them a bit and now the engine runs like a top... This engine was repowered using a tape player motor, by the way. I pulled the original brass worm from the cheapo LL motor and pressed it on to the new one, then fixed it in place with epoxy and styrene shims. I mentioned this on rmr a long time ago, saying it hadn't worked well...turns out the electrical pickup was the problem all along. While testing this engine, I also tried out an ancient KF power pack, bought for $1 at the train show last month. Any of you old-timers ever used these? It has a variable transformer (not an autotransformer, however) for speed control, no overload protection, and a pair of (selenium?) rectifiers that get extremely hot...is that normal, or should I replace them with newer parts? Cordially yours: Gerard P. President, the electrically more competent Sparta Railroad > Dear folks: > [quoted text clipped - 24 lines] > Gerard P. > President, the electrically more competent Sparta Railroad Under normal load the selenium rectifiers should get warm, not hot. Perhaps you should replace them with modern silicon diodes. If one of these selenium rectifiers does 'cook' itself, you'll love the aroma! That experience was fairly common back in vacuum tube electronics days! On the other hand, if they're on the outside of the power supply, they look 'neat', with lots of cooling fins. Often they were outside, to allow convection cooling, though some were inside, and heat-sinked to the instrument case. Perhaps you could just leave them in place, and disconnect and bypass them electrically? Dan Mitchell ============ Dan Mitchell: Aroma? Hmm...could you describe this aroma? Cordially yours: Gerard P. > Dan Mitchell: > > Aroma? Hmm...could you describe this aroma? > > Cordially yours: > Gerard P. Hard to describe, but unpleasant and potent! Distinctly different than roasting bakelite or boiling silicon oil (which likely has PCB's in it too). Dan Mitchell ============ Dan Mitchell: Would you say the smell had a note of garlic or onions? Cordially yours, Gerard P. pawlowsk002@gannon.edu spake thus: > Would you say the smell had a note of garlic or onions? [referring to smell of hot components in old power pack] Interesting you ask: I've always associated the smell of ozone (generated by electric arcs, for instance by motors with sparking brushes) with the smell of garlic.  Signature... asked to comment on Michigan governor George Romney's remark that the army had "brainwashed" him in Vietnam—-a remark which knocked Romney out of the running for the Republican nomination—-McCarthy quipped, "I think in that case a light rinse would have been sufficient." (Eugene McCarthy, onetime candidate for POTUS) > pawlowsk002@gannon.edu spake thus: > [quoted text clipped - 5 lines] > (generated by electric arcs, for instance by motors with sparking > brushes) with the smell of garlic. People's sense of smell, or recall of odors, seems to vary widely. They relate all sorts of divergent smells to any one smell. I've encountered this in chemistry classes on numerous occasions. Electronics work creates all manner of odors ... hot soldering irons, solder flux, burnt bakelite or other plastics (insulation, etc.), ozone, burnt selenium rectifiers, contact cleaners, flux remover, etc. Dan Mitchell ============ > Dan Mitchell: > > Would you say the smell had a note of garlic or onions? > > Cordially yours, > Gerard P. A reasonable description, with a touch of burnt plastic for accent. I haven't cooked one off for perhaps 25 years, but it's definitely pungent! Dan Mitchell ============ >> Aroma? Hmm...could you describe this aroma? Like somebody crapped in a toaster and then turned it on. >>>Aroma? Hmm...could you describe this aroma? > > Like somebody crapped in a toaster and then turned it on. Worse! And they will go bad at some point. My other hobby is antique radios, and the universal agreement is to replace or bypass these things because it is only a matter of time before they fry. And, as they age, they pass less voltage, which most likely is not a problem with trains, but is with radios. Best Regards, DAve >Worse! And they will go bad at some point. My other hobby is antique >radios, and the universal agreement is to replace or bypass these things >because it is only a matter of time before they fry. And, as they age, >they pass less voltage, which most likely is not a problem with trains, >but is with radios. Mine too - and i couldn't agree more!!! >>>> Aroma? Hmm...could you describe this aroma? >> [quoted text clipped - 9 lines] > > DAve They don't all go bad, at least not in a hurry. I have some that are over 50 years old that stil work, but perhaps not as well as they once did. The added voltage drop you mention may well be the precursor to failure, as well as the source of the excessive heat mentioned by the OP. Still, it's a good idea to avoid the issue and just bypass them with silicon diodes. The diodes are a LOT smaller anyway, and can usually be located somewhere unobtrusive, leaving the old seleniums just for 'show' (expecially if it's a historic power pack). They often LOOK impressive. Dan Mitchell ============ I have a Scintilla Rail and Power Works, inc. power supply. The selenium's on it are a four bank 4" x 6". I bypassed them but they are impressive. > >>>> Aroma? Hmm...could you describe this aroma? > >> [quoted text clipped - 21 lines] > Dan Mitchell > ============ > I have a Scintilla Rail and Power Works, inc. power supply. The > selenium's on it are a four bank 4" x 6". I bypassed them but they are > impressive. Ya know, if you added a big Jacob's Ladder spark gap on top it would be even more impressive. SignatureSteve >Ya know, if you added a big Jacob's Ladder spark gap on top it would be >even more impressive. Grandpa Munster would be proud!!! >Under normal load the selenium rectifiers should get warm, not hot. >Perhaps you should replace them with modern silicon diodes. >If one of these selenium rectifiers does 'cook' itself, you'll love the >aroma! That experience was fairly common back in vacuum tube electronics >days! These are the first things i replace in old radio equipment as they pass a poisonous gas when they burn - not a good thing. pawlowsk002@gannon.edu spake thus: > Well, I asked a question about wheel wipers and got a lot of answers, > so I went to inspect one of the worst electrical offenders on the [quoted text clipped - 7 lines] > shims. I mentioned this on rmr a long time ago, saying it hadn't > worked well...turns out the electrical pickup was the problem all along. Congrats on your resourcefulness (and going-against-the-grainness: you know, "thou shalt only use Official Model Railroad Motors in thy locos"). > While testing this engine, I also tried out an ancient KF power pack, > bought for $1 at the train show last month. Any of you old-timers > ever used these? It has a variable transformer (not an > autotransformer, however) for speed control, no overload protection, > and a pair of (selenium?) rectifiers that get extremely hot...is that > normal, or should I replace them with newer parts? Nah, leave 'em in; as I remember from my boyhood, selenium rectifiers always ran pretty hot (hence the mega-cooling fins). It's more "prototypical" that way! Signature... asked to comment on Michigan governor George Romney's remark that the army had "brainwashed" him in Vietnam—-a remark which knocked Romney out of the running for the Republican nomination—-McCarthy quipped, "I think in that case a light rinse would have been sufficient." (Eugene McCarthy, onetime candidate for POTUS) |
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