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In the Forum: Melquiades Amplifier
In the Thread: Gas voltage reference 0A2 tubes.

Post Subject: New Jersey, what exit?Posted by floobydust on: 1/19/2009

Hi all,

Just joined the cat house... funny seeing the mention of some old stomping grounds here... like Bendix in Red Bank, NJ... they were one of my accounts back in the late 70's. As some of you may know, the U.S. Army's electronics center was just up the street from Bendix, about a mile north... Fort Monmouth (also one of my accounts from way back). In between them was Atkinson & Smith, the best place for military surplus electronics, you can only imagine why... literally tons of mil-spec goodies for pennies, like Jan 807 tubes for 95 cents back in the late 60's and early 70's, all compliments of US taxpayer $$ after tube technology was being phased out. The parts supply was wonderful, sockets, resistors, capacitors, tubes, transformers, switches and tons more... all at rock-bottom dirt cheap prices. I miss the place.... Mr. Smith sold it back in the mid 80's... I was there buying some remaining bits and pieces when he told me. I still have some parts stock from those days even now.

Case in point, I have many of the OA2 and OB2 gas VR tubes, mostly NOS Jan-spec Sylvania. These are excellent tubes in general. Also note that these have some small amount of radioactive gas in them and is clearly marked in the printing. I've used these for decades as shunt regulators in preamps and if treated well will last a very long time. They are most stable if you regulate the current flow. Running them too hot will certainly shorten their life span and their voltage will drift as they burn out. Using too large of a bypass capacitor will also shorten their life span as the igniting voltage is quite a bit higher than their regulating voltage and internal arcing with higher currents from the large bypass capacitors will damage them.

As for the 5651 (A and WA), these are not designed for shunt regulation but for a tight spec reference tube and much lower voltage than typical shunt regulators. Again, staying within the narrow current range (1.5ma ~ 3.5ma) is critical for best performance. I've used these over the years as well with very good results. You can find some good background and classic regulator circuits in older ARRL handbooks... mid-50's.

Regards, KM

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