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Old 2nd October 2006, 04:22 PM   #1
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Default Gas-Rectifier power supply

Hi!

I decided to make universal, high voltage, power supply with adjustable output voltage and this is wath I came up to... (It supposed to be power supply for the audio line amplifiers).
It is a virtual battery with the adjustable output voltage. I didn`t wanted to use "active" regulation, nothing fancy...


The MOST interesting part of this design is that I used "gas stabilizer" russian tube (SG3S), for voltage reference and an old, full wave rectifying gas tube (AX50 - Philips miniwatt).
I never used AX50 and I disovered that when this tubes deliver more then 90-100mA it starts to shine nice blue light. When i load it with 120mA and more the whole tube shines out A WONDERFULL AND MAGICAL blue lite!!! So:
Did anyone used this tube and why the blue light starts at 100mA and more... Is this normal for all gass rectifiers? BTW maximum anode current of the AX50 is 275mA.

I`ll take a picture of this construction in next couple of days, this is the schematic, for now.

I tried it with my (EI)ECC82 line amplifier and it is very quiet and my preamp sounds much better.


CHEERS!
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Old 2nd October 2006, 04:23 PM   #2
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AX50
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Old 2nd October 2006, 04:35 PM   #3
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The AX50 looks like an 83 rectifier. A bright blue glow is normal. The only thing to watch out for is warm up time, 30 seconds or so should be enough.
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Old 2nd October 2006, 05:33 PM   #4
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Ok, but why the blue light starts at 100mA and more? If the current is less then 100mA, there is no blue light but it works ok. Is this tube wasted(broken)? I got two of these beauties and they act the same way...

I would love to get that blue glow with my line amplifier (about 40mA).
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Old 2nd October 2006, 07:19 PM   #5
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anyone?
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Old 2nd October 2006, 07:31 PM   #6
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Can this be an explanation:

hard vacuum

A fuzzily defined pressure range of vacuum. The fundamental way most people seem to use the word is as arbitrarily vacuous - having a low enough density for any phenomenon relying on low pressure. Density in vacuum can be measured in either particles per cubic meter or in a pressure measure, such as atmospheres, Pascals, or millimeters of mercury.

For reference, here are some quantitative measures of vacuum:

low vacuum 105 - 103 Pascals
medium vacuum 103 - 10-1 Pascals
high vacuum 10-1 - 10-4 Pascals
very high vacuum 10-4 - 10-7 Pascals
ultra-high vacuum (UHV) 10-7 - 10-10 Pascals
extreme-ultrahigh vacuum (EHV or XHV) < 10-10 Pascals
space-vacuum 10-15 Pascals
highest man-made vacuum (circa 2002) 10-10 Pascals
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Old 2nd October 2006, 07:33 PM   #7
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Or this: ( I do not know much about it, this is just from a debate on a forum in Norway)

"1) FLUORESCENCE. This type of glow is normally dark blue. It can appear outside the anode, on the glass surface inside the bulb, and as spots on other parts inside the tube. The spots may have the appearance of stains. With very used tubes, you can sometimes see a faint stain on the glass, at the position where the fluorescence appears. In most cases, you will find it with power tubes. It results from electron bombardment on glass taking place within the tube. It generally has no negative effect upon the performance, and in fact, tubes displaying this phenomenon are particularity good with respect to having a high vacuum. Mesh plate tubes will display this blue glow under high Anode current, since these have holes in the Anode, letting electrons pass. You may also see it in tubes like EL34, or 6550, which have holes in the anode. These holes are for adjusting the grids during production. Typical for this kind of glow is, that if you hold a conductive surface against the fluorescent spots, (if on the glass) the spot will change it's shape. (The electrons take a different path)"
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Old 2nd October 2006, 08:33 PM   #8
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Quote:
You may also see it in tubes like EL34, or 6550, which have holes in the anode.
Yes I know but I think that`s not a issue here.
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Old 3rd October 2006, 02:34 AM   #9
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The tubes are most likely fine. I experimented with 866s for a while and noticed the same behavior. At low currents the glow was barely visible but then after a certain point they really lit up.
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Old 3rd October 2006, 02:32 PM   #10
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We are talking about "gas" rectifiers here. There is intentional "gas" inside the tube so there is no "hard vacuum".

I use the word "gas" in parentheses because the "gas" is often Mercury vapor. This is obvious because the Mercury condenses into a liquid at room temperature. In some tubes the "gas" actually is gaseous Argon, Xenon or a mixture of "inert" gasses. Each of these gas mixtures have different "glow" properties. I have been using 3B28's (Xenon) to replace 866's (drop in). These have no toxic mercury, but no blue glow. There is a very pale violet glow whrn operated near max current. They do not radiate noise that mercury tubes do either.

It is important to understand that the "gas" is present to lower the on resistance or voltage drop across the tube. At low currents the tube functions as a normal rectifier tube, the "gas" does not ionize. As the current (and voltage across the tube) increases the "gas" will ionize and conduct heavily, reducing the losses through the tube. This happens on a cycle by cycle basis. The glow that you see is the gas ionizing in a fashion similar to a neon light.

The ionization point is controlled by the vapor pressure of the gas inside the tube. The vapor pressure is closely related to the temperature of the tube. These parameters are set up when the tube wqas designed and manufactured.

If the gas is too hard to ionize, the tube will have a higher voltage drop, but be able to handle more PIV. If the gas is too easy to ionize the tube will glow at a lower current, but it will be possible to ionize the gas in the reverse direction, which is a really bad thing for a rectifier tube!

I am not familiar with that particular tube, but this behavior is probably normal.

The oddball exception to this rule is the 0Z4. This is a gas rectifier that has NO HEATER! It was developed for 1940's vintage car radios. Most are in metal envelopes, but glass versions can be found. This tube was intended to operate with a square wave voltage source, but operation at low power with a sine wave is possible. The directionality of the current flow through the gas was controlled by the (rather odd) electrode shape. These tubes require a minimum current to operate (30 mA) Operation below this value will cause early death. Max on the later versions is 110 mA.
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