testing voltage on tube filament, without the tube
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 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 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 __________________ "To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
 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?
 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. __________________ Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001. Argentine Ham Radio LW1DSE since 1987.
JMFahey
diyAudio Member

Join Date: Mar 2009
Location: Buenos Aires - Argentina
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?

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