On 6/28/06, Spehro Pefhany <speff@interlog.com> wrote:
> At 08:29 AM 6/28/2006 -0700, you wrote:
> > > I replaced one of of the (series string) bulbs with a (carefully
> > > insulated) 1N4007 to knock the voltage down to 70% of line and get several
> > > years lifetime 24/7.
> > >
> >
> >
> >Which reminds me... Some projectors use 70V lamps. I assume they get the
> >70V by half wave rectifying the 120VAC line.
>
> That would give you ~85VAC. It also might be prohibited because of the
> unpleasant input waveform. Maybe they regulate the voltage fed to those bulbs.
>

Are you referring to film projectors?  They use a transformer for the
bulb voltage. I believe this is to keep noise out of the audio
preamplifier.  I found this out when I made an SCR dimmer for a
projector.

Regards,
Mark
markrages@gmail
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