Firstly could someone confirm it is a CuO rectifier
Yes I can confirm that it is a Copper Oxide rectifier ! If I can find the right box probably have a new one kicking around. Made by Ferranti if I recall. Antique Radio may have some data on it !
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Baron.
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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.
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.
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seems these testers drove the valves to be tested with ac as very difficult to get a regulated DC supply over the required ranges, wheras for well enough regulated ac, only required different taps on the mains transformer.
It is my understanding that both Selenium and Copper rectifiers look the way they do not for cooling but for how the materials were assembled. Just an FYI.
They only work half the time. :) Here's a (not the best) schematic as far as I've gotten things traced for an old piece of medical gear:
I'm not sure what you would call this topology; a self-rectifying oscillator?
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Tim Mullen
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