Recently acquired HP330B vacuum tube distortion meter. Since HP part #s from 1950s probably not much help now maybe one of the engineer types on the forum could recommend modern replacements that would work. Meter probably needs to read AC volts up to at least 100kHz (5th harmonic of 20kHz).
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As the tubes 6H6 will allow 4mA i think 1N4148 will do just fine. And
it's the cheapest diode you will ever find!
I agree with Peter about a 1N4148 diode. But just FYI a 1901-0027 diode crosses to a 1N4392. Per my diode D.A.T.A. book it's a 15piv Si. D07 with a 500pS Trr (reverse recovery time) made by Hughes, a division of Hughes Aircraft. (73293) Of course keeping it original is easy since 6H6s are plentyfull and cheap.
Here I was trying to unload some 6AL5...easily adapted to the situation w a new socket.
I've scrounged many Eico and Heath VTVM's -- they used germanium diodes in that type of circuit.
I've scrounged many Eico and Heath VTVM's -- they used germanium diodes in that type of circuit.
HP original diode for sale: Ηλεκτρονικά Ανταλλακτικά και Εξαρτήματα Qservice Electronics - HP - Agilent Repair Part, 1901-0027 Diode
I'd suggest substituting the very fast, very low capacitance 1N4149 (ends in niner). Half of the capacitance of an 1N4148. Buy 20 of them for 8 cents each (!) and test them on your DVM's diode-test feature. Choose the two that are most closely matched. Done.
Mouser sales page
I'd suggest substituting the very fast, very low capacitance 1N4149 (ends in niner). Half of the capacitance of an 1N4148. Buy 20 of them for 8 cents each (!) and test them on your DVM's diode-test feature. Choose the two that are most closely matched. Done.
Mouser sales page
I'm kind of embarrassed. Turns out the unit is a later model which came with the diode modification. But good to know in case there is a problem and they need replacement.
Just wanted to say a quick "thank you" for all those replying in this thread with these diode substitutes. Just a little while ago, I was able to get my HP 334a distortion analyzer up and running thanks to those replies. Its old 1N4392 diodes didn't survive well. Ended up using my last two 1N4148's. I'll check at higher frequencies than I have so far and see how a full calibration ends up.
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