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 Post subject: VR-150 how does it work?
PostPosted: Jan Wed 13, 2021 8:58 pm 
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Can someone explain to me how a VR-150 works? What pins do what, what the tube does to the 120VAc?.....


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 Post subject: Re: VR-150 how does it work?
PostPosted: Jan Wed 13, 2021 10:05 pm 
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0D3-A/VR150 - Voltage Regulator
The 0D3-A is a two-element gas filled, cold cathode voltage regulator. It is designed to provide a regulated output of approximately 150 volts. A jumper connected in the base between pins 3 and 7 provides the designer with several possible connections to ensure protection of associate components in case the regulator is removed from the socket. Except for bulb, this type is interchangeable with 0D3 tubes. Also known by US military identifier "VT-139", "VT-139/VR150-30"


https://www.tubesandmore.com/products/v ... -regulator
The tube is not used in A/C circuits.

DM


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 Post subject: Re: VR-150 how does it work?
PostPosted: Jan Thu 14, 2021 12:17 am 
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Here’s a direct link to the tubes spec sheet from the page devilmist linked you to. If you’ve not been to those pages before they can be confusing sometimes with all the advertising they try to get in:

https://www.tubesandmore.com/sites/default/files/associated_files/0d3a.pdf

As he said, the gas regulator should never see AC. It kind of connects across the HV B+ line and serves to drop it to a lower B+ and keep it steady at that voltage over a range of varying load currents. The voltage it regulates down to as well as the range of currents are found in the spec sheet.

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 Post subject: Re: VR-150 how does it work?
PostPosted: Jan Thu 14, 2021 12:36 am 
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The gas mix (and pressure) have an ionization voltage of 150V. As current increases the ion flow increases without much change of voltage. There's an internal jumper that can be wired in series with the regulated B+ to cut off the voltage if the tube is pulled. I've also seen it wired in series with the 115V input to prevent operation with the tube removed.

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 Post subject: Re: VR-150 how does it work?
PostPosted: Jan Thu 14, 2021 1:01 am 
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If the original poster is more comfortable with solid state devices, the VR150 is basically a 150 volt zerer diode....


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 Post subject: Re: VR-150 how does it work?
PostPosted: Jan Thu 14, 2021 7:06 am 
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jim rozen wrote:
If the original poster is more comfortable with solid state devices, the VR150 is basically a 150 volt zerer diode....


You would probably need a 10 watt stud rectifier diode, though.

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 Post subject: Re: VR-150 how does it work?
PostPosted: Jan Thu 14, 2021 8:40 am 
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Pins 3 & 7 are connected to a internal jumper which can be used to open the power supply circuit (either on the 117V primary side or more often in the secondary DC or AC circuit) to prevent operation if the tube is removed from the socket (safety feature). These pins are not allways connected and are not needed for the correct operation of the tube, though a series limiting resistor is allways mandatory. The working is similar to a Zener diode but VR tubes needs a minimum (starting) voltage or they won't fire and there's also a min - max. current operating limits to stay within to keep the tube in his regulating area and not damaging it by exceeding the max. ratings.


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 Post subject: Re: VR-150 how does it work?
PostPosted: Jan Thu 14, 2021 3:21 pm 
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Location: Long Island NY
Quote:
If the original poster is more comfortable with solid state devices, the VR150 is basically a 150 volt zerer diode....


That's a rather superficial comparison. The VR-150 is in a broad class of devices called gas discharge tubes which includes things like neon bulbs and fluorescent lamps. Essentially there is a gas or a mixture of gasses in the tube at low pressure with some electrodes inserted. When the voltage reaches a certain point the gas ionizes and conduction begins. The exact voltage depends on the gas mixture and how the electrodes are treated or prepared.

One thing all gas discharge devices have in common is negative resistance. What this means is, as the current through the tube is increased, the voltage drop decreases. This is the opposite of normal reistance where the voltage drop increases with the current. For this reason, there always has to be some resistance or impedance in series with the device, otherwise the voltage drop across the device would try to fall to zero and the current would increase until the device was destroyed or the fuse blew. But by proper design of the tube and the circuit it is in it is possible to make use of this effect to hold a voltage constant, i.e. a voltage regulator. As the voltage tries to increase, a VR tube presents less voltage drop thanks to its negative resistance. The current through it therefore increases faster than it would through a normal resistor. This tends to pull the voltage down through the load resistor and the output voltage thereby remains more or less constant.

Thing is, in order to achieve this effect at a predictable voltage, the electrodes in the tube are processed and coated with specific materials. The application of AC to them would reverse the current through the tube and damage the coatings on the electrodes, thus ruining their use as DC voltage regulators. If you want to run AC through a gas discharge device, nearly all neon and argon lamps, tubes, and signs have electrodes that are meant for AC operation.

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