testing voltage on tube filament, without the tube

spartan · 1st February 2013, 04:12 PM

I would like to adjust the tube heater voltage without using the tube. The tube rating is 5V/2A. I believe I can use a resistor in its place with the same effect, but I have never tried. Can someone confirm what should be the resistor's resistance and power rating? And if this is a good method?

Thanks!

kevinkr · 1st February 2013, 04:25 PM

Yes, this is a good technique. Use ohms law to calculate the required resistance and power..

At least double the rated power of the resistor based on calculation.

R = E/I where E is the operating voltage and I is the desired current.

P = I x E

spartan · 1st February 2013, 04:33 PM

Hi,
Thanks for the fast reply.
So for the 5V/2A tube it would be a 2.5ohm resistor rated at 20W, that's it?

Osvaldo de Banfield · 1st February 2013, 05:33 PM

Yes, OK, but use a higher wattage resistor, because it may run hot. Also, if the 5V is from a rectifier, be aware with the high voltages at their anodes.

Good luck.

JMFahey · 1st February 2013, 06:00 PM

Quote:

I would like to adjust the tube heater voltage without using the tube.

Just curious, haw are you going to "adjust the tube heater voltage"?
Where's such voltage coming from?
Is it a rectifier tube?
Does it have HV applied to it?

1st February 2013, 04:12 PM	#1
spartan diyAudio Member Join Date: Apr 2010	testing voltage on tube filament, without the tube I would like to adjust the tube heater voltage without using the tube. The tube rating is 5V/2A. I believe I can use a resistor in its place with the same effect, but I have never tried. Can someone confirm what should be the resistor's resistance and power rating? And if this is a good method? Thanks!

1st February 2013, 04:25 PM	#2
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	Yes, this is a good technique. Use ohms law to calculate the required resistance and power.. At least double the rated power of the resistor based on calculation. R = E/I where E is the operating voltage and I is the desired current. P = I x E __________________ "Extraordinary claims require extraordinary evidence." - Carl Sagan

1st February 2013, 05:33 PM	#4
Osvaldo de Banfield diyAudio Member Join Date: Dec 2011 Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina	Yes, OK, but use a higher wattage resistor, because it may run hot. Also, if the 5V is from a rectifier, be aware with the high voltages at their anodes. Good luck. __________________ LW1DSE

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1st February 2013, 04:33 PM	#3
spartan diyAudio Member Join Date: Apr 2010	Hi, Thanks for the fast reply. So for the 5V/2A tube it would be a 2.5ohm resistor rated at 20W, that's it?

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