[sdiy] Tubes in Synths [ was : Harry's Nightmare! ]

[John L Marshall]

I guess the circuit designer wanted a constant 105 volts drop from plate to
screen grid. Unusual design but it obviously works.

For those that want to work with tubes there is only (MHO) one definitive
text on the topic "Radiotron Designer's Handbook" by the Amalgamated
Wireless Valve Company Pty Ltd, Australia. This book was reproduced and
distributed by RCA in the 1930's to 1950's. It is available in used
bookstores and on ebay.

John
----- Original Message -----
From: Ingo Debus <debus at cityweb.de>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, November 10, 2001 8:45 AM
Subject: Re: [sdiy] Tubes in Synths [ was : Harry's Nightmare! ]


>
>
> harry wrote:
> >
> > We are talking REALLY tiny... the glass would stop it cold. Now if
> > you were to chew on one of them... you'd cut yourself...
> >
> > H^) harry
> >
> > John L Marshall wrote:
> >
> > > I check five reference books, there was no mention any radioactive
additive
> > > in zero tubes. The amount added to neons is not enough to be concerned
> > > about. Worry about all the fat in the brautwurst. The fat tastes sooo
good.
> > > Doesn't your 0C3 look really cool?
>
> Harry and John (and Doug too, who replied privately), thanks for
> clarifying. I was a bit worried because this amp is from the fifties or
> sixties, when people weren't so worried about radiation as they are
> today. As I bought it about 10 years ago, I thought it was a tube
> rectifier and it sure would go bad soon because of the bright glow.
>
> Next question is, why did they use this tube? Looking at the schematic
> (it's attached to the side of the amp chassis), it is used to drop the
> 405 volts to 300 volts for the power tubes' grids. The 0C3 is in series
> with the power supply, not like a shunt regulator in parallel with the
> load. Why didn't they use just a resistor divider?
> >From there the 121 volts supply for the preamp stages is derived,
> through a 10k resistor.
>
> Ingo
>
>