[Bret L]

On Jul 14, 8:45*pm, John Stone wrote:
On 7/14/10 8:37 PM, in article
, "Bret L"

wrote:
*They didn't have cheap silicon diodes, so you needed tube rectifiers,
not only for HV but bias as well unless you wanted to use a battery.
And a relay to open if no bias voltage was there and bring in a
cathode resistor.

Um, ever hear of a selenium rectifier? Mac, early Marantz, Fisher, Dynaco,
etc all had 'em for bias and dc heater applications. Yeah, they *wore out
after 10 years or so, but by then you had the silicon replacements.

Yes, but they were nasty. But for bias, not so nasty as to be
unthinkable. They were common. They didn't realize how toxic selenium
smoke was then, so it's a case of looking back through a different
perspective.

Cantonwine's battery charger book is very informative on them.

Tungar bulbs were another alternative. They had small ones. You wanted
a relay for protection still, though.