Wheel wipers redux; tape player motors ; KF transformers

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.

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 ============

snipped-for-privacy@gannon.edu spake thus:

Congrats on your resourcefulness (and going-against-the-grainness: you know, "thou shalt only use Official Model Railroad Motors in thy locos").

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!

Dan Mitchell:

Would you say the smell had a note of garlic or onions?

Cordially yours, Gerard P.

Like somebody crapped in a toaster and then turned it on.

snipped-for-privacy@gannon.edu spake thus:

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.

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

These are the first things i replace in old radio equipment as they pass a poisonous gas when they burn - not a good thing.

Mine too - and i couldn't agree more!!!

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 ============

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 ============

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 ============

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!!!