Jeff Wisnia wrote:

Franc Zabkar wrote:

On Sun, 16 Nov 2008 12:17:08 -0500, Jeff Wisnia
put finger to keyboard and
composed:


Taking another closer look at the schematic in that link you gave me
shows the "arrow half" of the symbol for that diode, but it was very
easy for me to overlook. (And perhaps you too, since you thought I'd
need a 24 volt bulb. G)

Jeff


Yes, I missed it. But even if I had seen it, I would have still needed
to be told that it was a diode.

- Franc Zabkar

But, I think I may have grabbed a bulb from the kid's model RR junkbox
that had a higher voltage rating than the 12-14 volts I thought it had.

Mentioning the successful repair to someone else got me a response that
running a 120 volt bulb off of 240 vac in series with a rectifier is NOT
equivalent to running it off of 120 vac without the rectifier and the
bulb will blow out rather quickly, because its filament is overvoltaged
quite a bit of the time.

I've got to think that one out a few more times before I'm ready to say
yes or no to it. Perhaps someone reading this post can point me to a
cite on the subject.


There was a lot of discussion, and arguments on
news:rec.antiques.radio+phono a while back. Basically, a diode removes
one half the cycle, or applies power for half the normal time. you
have to multiply by .707 to get the equivalent voltage.

240 VAC *.707 gives an equivalent of 169.68, minus the .6 volt drop
across the diode, which leaves approx. 169 volts. Channel Master built
some B&W tvs with a 'dropping diode', and a series filament string
totaling 84 volts.


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