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Dagwood 6th November 2011 12:42 AM

Voltage Doubler ?????
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Hi All

I'm planning a passive pre amp but would still like to see some glowing glass:D so plan to add a EM84 Vu meter (The Site for Electronics, Microcontroller, Tubes, Forum, PCB, Circuits, Onlineshop

I have a transformer with a 100v output and would like to use a voltage doubler to get close to the 250vdc needed using the design below. (option a)

My question is could I use a EB91 (6AL5) in place of the silicon diodes?


TonyTecson 6th November 2011 02:41 AM

6AL5's are low current diodes...try it an find out....

how much current do you need, i believe 10mA is obtainable....

Dagwood 6th November 2011 08:57 AM


I only need 3mA

Tried it today, seems to work fine though output voltage varies a fair bit between the 6AL5 and the EB91's I have? they are all used stock so I'm guessing the variance is due to age.

Anyone else used these??

barrymagrec 6th November 2011 12:17 PM

The difference in voltage between different valves is probably exacerbated by the relatively high peak current. You may only be taking 3mA but assuming even modest value caps the conduction angle will be very low and the peak current quite high - could even exceed the peak rating of 54mA for the EB91.

diecast 6th November 2011 02:30 PM

250v the easy way
When I made a level meter using that circuit I used a DC/DC converter I found on eBay designed as a power supply for nixie tubes - I powered that and the filament in the magic eye tube from a 12v wall wart.

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