• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Tube magic eye with em84-sensitivity?!

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#4
I have just had a play with the circuit in the link.


http://www.solderingpoint.com/projects/indicator_tube/indicator_tube.php

This is my new modified version..😀 (sensitivity is much better)

I modified the pin out for a different EM tube type..

C1 is now 0.047uF

Its running from the preamp input/volume control as the article says you can mod for a FET however it seems to be OK..

Regards
M. Gregg
 

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#5
NB

I did think about using a super-alfa pair (Darlington driver)
However I think the gain might be to much..YMMV 😀

Remember to use a polypropylene High voltage input cap!

You can drive the preamp section from a LV supply..depends on what you are doing..


Regards
M. Gregg
 
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#6
I guess,

the problem with this sort of thing is the 250V Dc for people not using tube circuits..

So just a few ideas you could use a nixie tube supply..

Or play with a few ideas.(I haven't tried these circuits)

High Voltage DC-DC Converter Single Transistor Oscillator Circuit

Practical Transistor Circuits

Remember you still need to know what you are doing..
Shock hazard!

You could remove R4 in the circuit and feed the preamp with 30V DC <<<adds safety ...and the tube from a converter..
Which is similar to what you posted..the board is 12V DC in with a nixie type supply..so it makes the HV DC. Post 3#
I guess if it works its cheaper to just buy the board.. 😀

Regards
M. Gregg
 
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#8
Tony,

If you do run the preamp without R4 remember to remove the zener (D1)..🙄
Just thought about it..I assumed you would already know about it!
Reference post 4#

Regards
M. Gregg
 
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#11
Tony44 said:
We need schematic (circuit) percent instead em81 have em84.🙁
Click to expand...

This is what I would try,

I would de-solder the tube socket from the board and hard wire it in like this then give it a try..if it doesn't work you can just put the socket back as it was for EM80..

NB its at your own risk..I do not know the circuit on this board.

Try it with these resistors in place first.
You could put a 10K from the board to pin 6.
Also a 150K from the board to link pin 9-7

Regards
M. Gregg
 

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