Electronics > Projects, Designs, and Technical Stuff

Strange AC current source..("variator"????)

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SK_Caterpilar_SK:
So recently I repaired a old vacuum tube voltmeter. And it has a weird bulb. Apparently its called a "variator" or some sort of thing. When I unscrew it its marked as "NARVA 3-9V 1,4A". According to the schematics (which I will include) its used as a very simple constant current regulator for heating the cathodes of the tubes. Seems like its basically a hot piece of wire just changing its rezistance based on teperature. And the reason im worried is that the wire inside looks almost crackled it has lighter noticeable spots and it looks original from the 1950s.

I tryed to find a replacement "bulb" and I did not. So im wondering if its possible to replace the "hot piece of wire" with a semiconductor current source that does not require much of aditional power to work. AC current source in short. Simply cant find anything at all. Any help is very much appreciated.

amyk:
That would be an https://en.wikipedia.org/wiki/Iron%E2%80%93hydrogen_resistor

SK_Caterpilar_SK:

--- Quote from: amyk on November 10, 2018, 12:27:18 am ---That would be an https://en.wikipedia.org/wiki/Iron%E2%80%93hydrogen_resistor

--- End quote ---

Thanks. Seems youre right. But the problem is that I cannot buy any of thhoose and I heard that you could replace it with some sort of circuitry with semiconductors. It would be nice If I could just replace it with a some sort os a circuit. If it would have been DC powered I would just replace it no question but its AC...

001:

--- Quote from: SK_Caterpilar_SK on November 10, 2018, 08:53:10 am ---
--- Quote from: amyk on November 10, 2018, 12:27:18 am ---That would be an https://en.wikipedia.org/wiki/Iron%E2%80%93hydrogen_resistor

--- End quote ---

Thanks. Seems youre right. But the problem is that I cannot buy any of thhoose and I heard that you could replace it with some sort of circuitry with semiconductors. It would be nice If I could just replace it with a some sort os a circuit. If it would have been DC powered I would just replace it no question but its AC...

--- End quote ---

Is it heater supply? You can use DC power

PA0PBZ:

--- Quote from: 001 on November 10, 2018, 10:15:36 am ---Is it heater supply? You can use DC power

--- End quote ---


+1  I was just going to comment the same.

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