Series connected stabilizer valves: questions
 

I have three 'known-good' 0B2 stabilizer valves. The 0B2 has a stab. voltage of 85 v. ± 1v. depending on its current and a striking voltage of about 130 v.
The idea is to connect three 0B2 valves in series to produce a stabilized voltage of 255 v. (255 = 85 x 3) from a 350 v. input voltage.

I used 220 kΩ resistors from the 350 v. to the two 'lower' valves to meet the striking voltage requirement and a 4k7 Ω resistor from the 350 v. to the first 0B2. Yet configured as a '255 v. stabilizer', the current drawn from the 350 v. supply is far less than my calculations predicted ??? - so as a '255 v. stabilizer', it doesn't work. The wiring is correct; my arithmetic makes sense - so what part/s of all this do I have wrong or do not understand?

All replies will be appreciated.

Al.

Re: Series connected stabilizer valves: questions
 

The 0B2 is 108V nominal, not 85V - what datasheet are you looking at?

Re: Series connected stabilizer valves: questions
 

The calculation for these valves is about 5mA for each valve + the load current from memory, so 220k for the lower valves is too much I think, each lower valve is only getting around 0.75mA or the middle valve is getting around 1.5mA, the lower one nothing.

Andy.

Re: Series connected stabilizer valves: questions
 

Hi Al, I may have some 280 or so volt stabilisers, a bit bigger than the OB2 valve though; but may handle a greater current.

Ed

Re: Series connected stabilizer valves: questions
 

Skywave,

First thought, apart from the obvious that they are 105 volt regulators, is do they all fully light when powered? You probably do not have enough voltage headroom to start with. Getting series regulators to strike and pass burning current can be a bit of an art, especially three in series...

You do not show your calculations so what current do the pull from your supply and what were you expecting?
Working on what you have and assuming they are all 'lit', 350 volts in and 315 volts 'regulated' out, so 35 volts drop, using your 4.7k limit resistor should see about 7.5mA? It might be necessary to actually add a small load to make it stable. A 100k, 1 watt resistor will load it by about 3mA.

So questions are, what stabilised voltage do you want and what current does it need to be?

Alan

Re: Series connected stabilizer valves: questions
 

There are circuits with diodes as well as resistors which put the regulators in parallel for firing and then in series for running. However, your first job is to use 85V regulators instead of 0B2.

Re: Series connected stabilizer valves: questions
 

0B2 data sheets with graph/formula etc:

http://www.mif.pg.gda.pl/homepages/f.../127/0/0B2.pdf

Lawrence.

Re: Series connected stabilizer valves: questions
 

Sorry about that: I made a silly typo. :-] That's what happens to me when it's late at night / early morning and my frustration level has exceeded a certain threshold. I am using 0B2 valves. I would also like to add that connecting stabilizers like this in series is something I've never done before.

Apologies to all who were similarly confused.

Al.

Re: Series connected stabilizer valves: questions
 

I might be inclined to go the wimp's way and buy some zeners :shrug:

B

Re: Series connected stabilizer valves: questions
 

Having now reviewed my above thinking, etc. I can now see that that thinking was clearly in error. I really shouldn't do things like this when its very late at night and most of my brain cells have gone to sleep! (Especially with voltages of these magnitudes. :devil:) But enthusiasm being what it is . . . :-) However, with a bit of a re-calc., etc., things are now working as they should.

350 v. in; 1k5 series resistor; 150 kΩ resistor from stabilized rail to anode of 2nd. valve; similarly, 220 kΩ resistor to anode of 3rd. valve. That puts about 1 mA start-up current into each of those two valves to initiate the striking voltage. The voltage across each valve is then as it should be. Current through the valves is approx. 20 mA.
On test, Vstab is 322 v. no-load; 320 v. at 20 mA. That is more than adequate for what I have in mind.

Al.

Re: Series connected stabilizer valves: questions
 

Bazz: using Zener diodes for this application. I ruled that option out on two grounds:
1. Past experience showed that the temp. coefficient of H.V. Zeners seriously degrades the stabilized voltage;
2. I have more N.O.S. 0B2 valves in stock than I am ever going to need.

Al.

Re: Series connected stabilizer valves: questions
 

Surely you only need the start up resistor to the second valve down, the two in series below have a total breakdown of much less than to 350V in, it can be quite a big resistor too. Or one across any valve.

Re: Series connected stabilizer valves: questions
 

Ooh, I didn't know that... good job that I have kept my sizeable stash of gas regulators, as I still have to finish off the re-build of my HRO.

B

Re: Series connected stabilizer valves: questions
 

What about trying an OA2 & OB2 in series, as used by HP in the 412A Voltmeter to provide 255V.

David

Re: Series connected stabilizer valves: questions
 

To avoid that problem, use a longer string of lower voltage zeners. Distributes the dissipation as well so you can use lower power ones.

Re: Series connected stabilizer valves: questions
 

Pat Hawker's "Technical Topics" offers this: it also works if replicated across a chain of series-connected glowtubes so each one 'sees' rather more of the supply-voltage until they are all ignited.

Re: Series connected stabilizer valves: questions
 

Thanks for the further replies: several ideas there that are new to me.
And on that sub-topic of 'things new', how about this . . .

I tested several 0B2 valves - they've been in my possession for decades and are all 'N.O.S'. They all carry the brand name Haltron and are all marked CV1833. All of them - except one - met the published spec. for an 0B2. The one that didn't performed excellently as 115 v. stabilizer. :o
I am not aware of any B7G-based stabilizer valve that has that voltage. :-/

Any ideas to explain that? :shrug:

Al.

Re: Series connected stabilizer valves: questions
 

255 v. is less than my stated need.
The production of that -ve. L.V. rail looked like something new to me - at first. But when it's re-drawn in a 'conventional' style, it then appears to be not new at all. Many have been the times I've struggled to understand cct. diagrams drawn 'American style', which, when 'translated', then become understandable.

Al.

Re: Series connected stabilizer valves: questions
 

I guess you wanted 3x108V (324V) instead of 3x85V (255V).

HP often used the 5651A 85.5V reference tube for the voltage regulation with either a valve or transistor based series regulator.
The 5651A has a lower current rating than the 0A or 0G series voltage reference tubes.

Not sure about the 115V one, the last faulty VR tube I found had a crack from one of the pins, I'm sure it lit up at first but I didn't check the voltage until until another fault occurred, the neon must have slowly escaped or mixed with air as the instrument warmed up. :shrug:

David

Re: Series connected stabilizer valves: questions
 

Where is the dividing line between lower and higher voltage zeners where the tempco deteriorates?

Since my last post I recalled that one PSU I built for my HRO HT used 3 zeners (75V ?) to control a MOSFET, thereby reducing the power level and thermal load on the zeners.


B