0B3 Glows Orange

Rob11966 · 31st May 2009, 12:03 PM

Hi all,

I am playing around with a bunch of 0B3 tubes (brand, Electronic Enterprises) and they glow orange. I was under the impression that the 0b3 had a blue/violet glow. The tube seems to be regulating OK. Does anyone know if this particular brand glows orange or do I have a problem with the tube?

Cheers,

Rob

barretter · 31st May 2009, 12:12 PM

You don't have problem : the colour of the glow depends on the mixture of gases inside the valve. Most British 85A2s that I've come across glow orange.

Rob11966 · 31st May 2009, 12:34 PM

Thanks Barretter - Then I do have a problem as I am looking for that violet glow!! I achieved this briefly when I removed the shunt resistor and powered up the tube. It flashed blue, popped and then tripped the circuit breaker

Unfortunately it does not glow at all now. Looks like I might have to look for some sylvanias.

Thanks again for the information.

Rob

barretter · 31st May 2009, 01:17 PM

Do you mean series resistor? There should always be a resistor from the raw supply to the anode of the regulator valve. What are you using the 0B3 for? Direct supply of regulated voltage to a circuit or as a voltage reference in a more complicated regulated supply. If you're using it in the first role you can only supply a maximum of 30mA to the circuit from a single 0B3.

kevinkr · 31st May 2009, 02:14 PM

Barretter is right, you pushed that tube into the arc region of operation which destroyed it. The regulated output voltage is a function of the gas mixture and the geometry of the tube. My understanding (perhaps mistakenly) is that gas mixture and pressure plays the dominant role.

I would be more concerned about the functionality that the tube provides than the color of the glow. All of the 10 or so OB3 I have on hand IIRC are orange glow types.

Rob11966 · 31st May 2009, 09:08 PM

Yes Barretter, the series resistor, sorry. I have about 20 of these tubes and wanted to see just how long the tube would last without the series resistor - not long. I am planning to use it as part of a bias circuit, so current draw wont be a problem.

Hi Kevin, you are correct of course but I was hoping for both functionality and looks. Obviously, the tube mentioned above now has neither.

Rob

barretter · 31st May 2009, 09:37 PM

Well you're going to have to have a minimum current of 5mA otherwise the valve will extinguish. Are you using them to feed screen grids?

Rob11966 · 1st June 2009, 03:39 AM

Yes, will have a power across the output of the tube in order to satisfy the minimum current draw. Interestingly, with respect to these tubes it was my understanding that they could supply a higher current to the circuit as long as the maximum current rating (in this case 30mA) was not exceeded through the tube. Some designs that I have seen show these tubes being used to supply circuits well in excess of the tube current rating, with the series resistor used to limit the current through the tube - I don't think that I have got this wrong but at least for my circuit, it's academic as the bias current is very small.

chrish · 1st June 2009, 05:56 AM

Hmmm, what are you building now Rob

Colt45 · 1st June 2009, 06:12 AM

I've got some ST shaped sylvania and.. dunno, some other brand. They glow a kind of purpley white.. not as purpley as an 0D3, though.

Then I've got a couple raytheon -GT types, they glow orange (and reg more like 95V rather than 90ish..)

31st May 2009, 12:03 PM	#1
Rob11966 diyAudio Member Join Date: Jun 2007 Location: Australia	0B3 Glows Orange Hi all, I am playing around with a bunch of 0B3 tubes (brand, Electronic Enterprises) and they glow orange. I was under the impression that the 0b3 had a blue/violet glow. The tube seems to be regulating OK. Does anyone know if this particular brand glows orange or do I have a problem with the tube? Cheers, Rob

31st May 2009, 02:14 PM	#5
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	Barretter is right, you pushed that tube into the arc region of operation which destroyed it. The regulated output voltage is a function of the gas mixture and the geometry of the tube. My understanding (perhaps mistakenly) is that gas mixture and pressure plays the dominant role. I would be more concerned about the functionality that the tube provides than the color of the glow. All of the 10 or so OB3 I have on hand IIRC are orange glow types. __________________ www.kta-hifi.net

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31st May 2009, 12:12 PM	#2
barretter diyAudio Member Join Date: Apr 2003 Location: West Yorkshire, UK.	You don't have problem : the colour of the glow depends on the mixture of gases inside the valve. Most British 85A2s that I've come across glow orange.

31st May 2009, 12:34 PM	#3
Rob11966 diyAudio Member Join Date: Jun 2007 Location: Australia	Thanks Barretter - Then I do have a problem as I am looking for that violet glow!! I achieved this briefly when I removed the shunt resistor and powered up the tube. It flashed blue, popped and then tripped the circuit breaker Unfortunately it does not glow at all now. Looks like I might have to look for some sylvanias. Thanks again for the information. Rob

31st May 2009, 01:17 PM	#4
barretter diyAudio Member Join Date: Apr 2003 Location: West Yorkshire, UK.	Do you mean series resistor? There should always be a resistor from the raw supply to the anode of the regulator valve. What are you using the 0B3 for? Direct supply of regulated voltage to a circuit or as a voltage reference in a more complicated regulated supply. If you're using it in the first role you can only supply a maximum of 30mA to the circuit from a single 0B3.

31st May 2009, 09:08 PM	#6
Rob11966 diyAudio Member Join Date: Jun 2007 Location: Australia	Yes Barretter, the series resistor, sorry. I have about 20 of these tubes and wanted to see just how long the tube would last without the series resistor - not long. I am planning to use it as part of a bias circuit, so current draw wont be a problem. Hi Kevin, you are correct of course but I was hoping for both functionality and looks. Obviously, the tube mentioned above now has neither. Rob

31st May 2009, 09:37 PM	#7
barretter diyAudio Member Join Date: Apr 2003 Location: West Yorkshire, UK.	Well you're going to have to have a minimum current of 5mA otherwise the valve will extinguish. Are you using them to feed screen grids?

1st June 2009, 03:39 AM	#8
Rob11966 diyAudio Member Join Date: Jun 2007 Location: Australia	Yes, will have a power across the output of the tube in order to satisfy the minimum current draw. Interestingly, with respect to these tubes it was my understanding that they could supply a higher current to the circuit as long as the maximum current rating (in this case 30mA) was not exceeded through the tube. Some designs that I have seen show these tubes being used to supply circuits well in excess of the tube current rating, with the series resistor used to limit the current through the tube - I don't think that I have got this wrong but at least for my circuit, it's academic as the bias current is very small.

1st June 2009, 05:56 AM	#9
chrish diyAudio Member Join Date: Oct 2003 Location: Sydney	Hmmm, what are you building now Rob

1st June 2009, 06:12 AM	#10
Colt45 diyAudio Member Join Date: Feb 2002 Location: Canada	I've got some ST shaped sylvania and.. dunno, some other brand. They glow a kind of purpley white.. not as purpley as an 0D3, though. Then I've got a couple raytheon -GT types, they glow orange (and reg more like 95V rather than 90ish..)

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