N_Cook wrote:

nesesu wrote in message
...
On Apr 8, 2:19 pm, "N_Cook" wrote:
If the reverse capability of CuO is only 6 volts how can a 6 disc one be
used for anode/plate supply?

Copper oxide was used for low voltage rectifiers. For anode supply
rectifiers they used selenium. Selenium rectifires were most commonly
seen with cooling fins, but if the dissipation was low, conduction
cooling through the mounting stud was adequate. What you showed could
easily be a selenium type, and selenium has a rating of about 30-50V
per plate so a 6 plate would be good for 180-300V.

The rectifier in the Heath V7-A VTVM was a tiny stud mounted block [~
5/8" cube] and it was rated, IIRC, for 50mA and 150V.

Neil S.

There is no HT capacitor associated with the anode/plate HT, what is the
result of feeding high voltage ac to the anode/plate of a tube/valve? and
then just rectify a small ac voltage for feeding the meter , for testing
purposes


Copper rectifiers were used to convert DC meters to AC meters. Look
at the schematic of old VOM with AC/DC functions. Copper rectifiers
have a very low forward drop, and the use of another type of rectifier
will change the calibration. A silicon diode is not a good replacement
in most circuits. A modern replacement would be an 'Ideal Rectifier'
circuit, using an opamp to offset the forward voltage drop.

http://en.wikipedia.org/wiki/Precision_rectifier has a brief
description. Several semiconductor OEM cover the details in their
application notes. My collection is on another computer right now, but
ON, national, or anyone who makes opamps should have one in their list
of application notes.


--
And another motherboard bites the dust!