Obscure, I know. :)
I looked through my GE "Essential Characteristics" book and only found two. 6HJ8. 6AS8. Huh. I thought there'd be more of those. Doesn't seem like an unreasonable thing to want. Anything I missed?
There are a number of compactrons that seem to have it. High current filaments.
The 6JU8 is a 9 pin quad diode with 4 independent plates and two pair of tied cathodes.
The 6BF8 is a 9 pin sextuple diode with 6 independent plates and one cathode.
Obscure, I know. :)
Easy:
There's also a couple tetrodes (12EM6, 6FA7), and who knows how many industrial and European or other designations are missing that you'd need to search with a different character to find.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website:
The Philips/Mullard code for that specification would be EAF8n, where 'n' is a number (or EAL8n if it is a power pentode), but I don't recall ever finding a valve with that designation. There were a few EBF8n, with double diodes but a common cathode.
Another alternative is to diode-strap the triode section of an ECF8n, there are plenty of those and some of them have separate cathodes. Join anode to grid if you want it to handle a lot of current, join anode to cathode and just use the grid as the diode anode if you want low stray capacitance, join grid to cathode and just use the anode if you want to use it on high voltages.
-- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
Cool, thanks!
The 6BY8 has a wimpy pentode and a beefy diode. The 6HJ8 has a beefy (transconductance is OVER 9000!!!) pentode and a wimpy diode.
Yo, Adrian,
Welcome back. You've been sorely missed.
Cheers
Phil Hobbs
I seem to recall there being some gotcha in using a triode strapped to a diode but I can't remember what it was. I read it was done sometimes by radio mfgrs in the Great Depression to save some pennies.
An even more obscure tube was the Loewe 3NF with three triodes but also some resistors and capacitors in the same envelope
Jist add a resonant circuit at the input and a speaker at the output and you had a complete single tube receiver :-)
What was it used for ? A 6 input OR gate in diode resistor logic ?
That configuration (common cathode, six anodes) was common in mercury filled rectifiers. A single tube rectified the three phase AC feed into DC capable of feeding trams and trolley buses.
Thanks. I've been lurking all the time, but haven't felt competent to comment on these new-fangled semiconductor whatnots.
-- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
There may be some disadvantages compared with a dedicated diode, but it does crop up in some commercial circuits where the requirements are not too onerous. Obviously the dissipation of a grid used as an anode is very limited and so is the reverse voltage rating of the grid-cathode insulation.
The extra capacitance of having an unwanted anode could be a problem in some circuits. It isn't a good idea to leave it floating, so it either has to be strapped to the cathode or to the grid - and either of those will result in extra unwanted capacitacnce compared with an equivalently-rated diode.
-- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
Also a number of triple triode Compactrons with independent, a pair, or all three, cathodes in common (typically TV color matrix amps).
The ones with other components inside, were a German tax dodge. It's amazing what lengths people will go to to avoid taxes. :^)
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
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