EM84 based VUmeter "lines" don't go to zero

[Danko]

Hello!

I have built this circuit:
http://www.jogis-roehrenbude.de/Leserbriefe/Anzeigeplatine/Anzeigeplatine.htm
The problem is, when there's no input signal to the circuit, then there are still lines on the tube.
The lines are a little bit longer than they:
http://www.jogis-roehrenbude.de/Leserbriefe/Anzeigeplatine/Fertig-Foto-EM87.jpg

What could be the problem? Could somebody help me? 🙂

 

[EC8010]

Do remember that "magic eye" tubes are not precision devices. What you're seeing is quite normal...

 

[jane]

Is there any difference if you ground the grid of the magic eyes (e.g. short the 1M2 grid-leak)? If yes, you might try to decrease the value of the grid-leak.

Just my 0.2dB

 

[anatech]

Hi Jane,

Just my 0.2dB

I like that!

EC8010 is right Danko. They were only ever meant for rough signal indication. Good luck on your project! It will look really neat.

-Chris

 

[coresta]

Hi! the NIXIE IN13 or 14 bargraphs look more linear . I've been testing one and linearity is my 0,5 dB 😉 😀

 

[Simpleton]

On my magic eye vu-meter, i simply biase the tube as a grounded cathode, for the fully closed voltage. Works a treat and it's simple! Just about 3 resistors and you're done.

 

[Danko]

Thanks for everyones response!!


If I short the 1.2M resistor, then the signal doesn't get to the tube, so that's not a solution.

I tried to insert a trimm.pot between the cathode and the GND. But when I started to increase the trim.pot's resistance, then lines started to grow longer.

When I turn off the amplifier, the lines are getting longer, when the B+ is decreasing.

Maybe the B+ isn't high enough in my amplifier? Under steady state, when all the tubes are warmed up, the B+ is 320V.