Changing AC heaters to DC

bereanbill · 15th May 2009, 10:57 AM

Is there any way to change heaters from AC to DC without adding a filament tranny ? Can I rectify the AC winding and the drop the voltage back to 6.3V ?

woody · 15th May 2009, 11:28 AM

You will have to take care of the current rating of the transformer.

If you have a 1A 6.3v transformer and use a full wave rectifier
and a big cap you should get ~ 6.8v dc . 6.3 x 1.41 = 8.82
but you will lose ~2v in the bridge rectifier more important
is that your avaliable current is now ~ .5A not 1A.

andRookie · 15th May 2009, 11:37 AM

It should not be any trouble. Just recitfy the ac, filter it with a CRC and adjust the resistance to get the right voltage. Be careful to calculate the power dropped over the resistor and make the margin like 50% or so. The resistor will be hot anyhow, but just control that it is not too hot when operating the circuit.

A big powerresistor or one of these resistors that you can mount on a cooling device might be an idea.

ErikdeBest · 15th May 2009, 02:14 PM

Hi Bereanbill

What are you trying to achieve? In some cases making DC out of AC can give more problems than solutions - and one such case is plain rectification and CRC filtering. Have a look at this site

If you are, for example, having HUM problems using AC I don't think you will solve them by simply rectifying and CRC filtering it.

Wavebourn · 15th May 2009, 05:59 PM

I use a Shottky diodes to rectify 6.3V getting 8V, or 12.6V getting 16V, then use a N-MOSFET and NPN transistor with one Zener and couple of resistors to regulate it. Why MOSFET? because it works down to zero volt drop-off.

Wavebourn · 15th May 2009, 06:32 PM

Here it is:
http://www.diyaudio.com/forums/showt...78#post1828878

15th May 2009, 10:57 AM	#1
bereanbill diyAudio Member Join Date: Jan 2009	Changing AC heaters to DC Is there any way to change heaters from AC to DC without adding a filament tranny ? Can I rectify the AC winding and the drop the voltage back to 6.3V ?

15th May 2009, 02:14 PM	#4
ErikdeBest mostly thinkerer diyAudio Member Join Date: Mar 2003 Location: Maputo - Mozambique	Hi Bereanbill What are you trying to achieve? In some cases making DC out of AC can give more problems than solutions - and one such case is plain rectification and CRC filtering. Have a look at this site If you are, for example, having HUM problems using AC I don't think you will solve them by simply rectifying and CRC filtering it. __________________ my surname is indeed 'de Best': neither misspelling nor snobbism! Ask SY!

15th May 2009, 05:59 PM	#5
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	I use a Shottky diodes to rectify 6.3V getting 8V, or 12.6V getting 16V, then use a N-MOSFET and NPN transistor with one Zener and couple of resistors to regulate it. Why MOSFET? because it works down to zero volt drop-off. __________________ If I disappear suddenly, that means I finally created a time machine and pushed wrong button that brought me to Stalin's Russia. In any experiment any result is the result. Even if it is negative.

15th May 2009, 06:32 PM	#6
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	Here it is: http://www.diyaudio.com/forums/showt...78#post1828878 __________________ If I disappear suddenly, that means I finally created a time machine and pushed wrong button that brought me to Stalin's Russia. In any experiment any result is the result. Even if it is negative.

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15th May 2009, 11:28 AM	#2
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	You will have to take care of the current rating of the transformer. If you have a 1A 6.3v transformer and use a full wave rectifier and a big cap you should get ~ 6.8v dc . 6.3 x 1.41 = 8.82 but you will lose ~2v in the bridge rectifier more important is that your avaliable current is now ~ .5A not 1A.

15th May 2009, 11:37 AM	#3
andRookie diyAudio Member Join Date: Apr 2006 Location: up north	It should not be any trouble. Just recitfy the ac, filter it with a CRC and adjust the resistance to get the right voltage. Be careful to calculate the power dropped over the resistor and make the margin like 50% or so. The resistor will be hot anyhow, but just control that it is not too hot when operating the circuit. A big powerresistor or one of these resistors that you can mount on a cooling device might be an idea.

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