[John Stone]

On 7/14/10 8:48 PM, in article
, "Bret L"
wrote:

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.

You're backtracking. Fact is, seleniums, not tubes, were the most common
rectifier in 50's and 60's consumer electronics for bias and heater
supplies. And a large chunk of companies used them for B+ rectification as
well. Series wired tv's often had a pair of big ones in voltage doubler
configuration. Another example being your beloved Marantz 7 which used a
half wave selenium stack for B+ and a full wave bridge for heater supply.
I've never seen tubes used in consumer products for bias rectifiers. As for
them being nasty, yeah, they stunk like hell when they blew up which wasn't
very often. As for toxicity, I don't know of anyone who was ever
injured-much less died-from a selenium rectifier. Do you? German companies
like AEG and Siemens made tons of selenium bridges for use in radios and hi
fi gear. The stacks were well sealed to keep the stink contained if they
blew.