Powering on HM85 Magic Eye

[Mahdi Al Husseini]

Hi there,

I've recently gained an HM85 tube that I would like to power up in a project, at this point time, purely for aesthetic purposes. I am having a difficult time deciphering the corresponding schematics, pulled from radiomuseum.org. If someone could assist, it would be appreciated.

Al

[HuggerMugger]

Pls check to see if it is equivalent with EM85. Maybe heater voltage different.

 

/M

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Virusfritt. www.avast.com

[Mahdi Al Husseini]

Hi,

Thanks for the response. It appears to be fairly different from the EM85, but essentially the same as the UM85 (with variations to the heater). I have attached both schematics for your reference

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[John Rehwinkel]

> I've recently gained an HM85 tube that I would like to power up in a project, at this point time, purely for aesthetic purposes. I am having a difficult time deciphering the corresponding schematics, pulled from radiomuseum.org. If someone could assist, it would be appreciated.

Pins 4 and 5 are the heater, and pin 3 is the common cathode. There's a built-in amplifier triode you can ignore (grid is pin 1, plate is pin 9). The display section has a deflection electrode on pin 7 and the target on pin 6. Hook the target to 160-250 volts or so and it should light up. Varying the voltage on pin 7 will change the amount of the target is illuminated. The diagram shows how to use a low level (0 to -13V) signal to control the display by using the triode, just hook the triode plate to the deflection electrode, and to your B+ supply via a high-value resistor (470k is what the diagram shows), then the low voltage signal at the grid will be amplified to control the deflection (this is how the tube is used in a radio to show tuning: the input comes from the radio's AVC voltage).

- John

[Mahdi Al Husseini]

Thank you John, this is immensely helpful

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