Strange mixer inputs

[Harry Bissell]

Alas, a filament can be a fragile thing... but they are actually good
non-linear resistors... slow, but good. Usually at least a 10:1 range can be
gotten without trouble... cold = low resistance, hot = high. Wein Bridge
oscillators often use a lamp as a "vca" for amplitude stability.

I've often considered them for industrial apps... but if I send a serviceman
into the BIG 3
(US Auto MFG) and he says "Bad Light Bulb..." my career is over....

Maybe they need Industrial DIY ????

:^) Harry

tomg wrote:

> I've used lamps for all sorts of things. They suck up current
> like a sponge. Any time I work on a transistor amp I use
> one of these..
>
> http://www.xavax.com/efm/guitar/warlock/page_006.html
>
> Once you get used to it you can set amp-bias by how
> brightly it glows. I've actually seen lamps used as emitter
> resistors instead of a .33 @ 5 (10) watts before. It's sort of
> a current limiting resistor.
>
> BTW I know about the broken link on page 4. I'll get it all
> fixed someday.
>
>  -tg
>
> ----------
> > From: KA4HJH <ka4hjh at gte.net>
> > To: synth-diy at mailhost.bpa.nl
> > Subject: RE: Strange mixer inputs
> > Date: Monday, October 04, 1999 4:16 PM
> >
> > >Apparently, these big monitor speakers have a fuse and a mini light bulb
> for
> > >protection. The fuse was fine, but one of the light bulbs was marginal!
> I am
> > >not sure electrically what the light bulb is being used for, but the
> problem
> > >was tracked down to that and replacing it did the trick!
> >
> > Sounds like a ballast. Non-linear thermistor.
> >
> > There was a guy whose model train kept derailing and shorting out his
> > electronic throttle, frying transistors, blowing fuses, or tripping
> > breakers constantly. He was too lazy to fix the track, but
> > fortunately a friend suggested putting a 12V taillight bulb in series
> > with the throttle. Now every time there was a short the filament
> > heated up from the increased current, increased its own resistance,
> > and limited the current enough to prevent anything from blowing.
> >
> > Don't know if that's what's going on here but it's a good story.
> >
> > Terry Bowman, KA4HJH
> > "The Mac Doctor"
> >
> > ICQ: 45652354