Transformer Leg Connection Question

mark845 · 5th August 2006, 06:27 PM

Hello All,

I am building a small tube amplifier where I need a B+ voltage after bridge rectification and CLC of 200 - 250 VAC. I cannot find a transformer manufacturer who makes a 75 - 0 - 75 VAC or single 150 VAC secondary. If I used a transformer with a 150 - 0 - 150 VAC secondary and only connected up one leg of the secondary, would there be any problems? Note that this transformer will also have a filament secondary.

Brian Beck · 5th August 2006, 06:45 PM

With a 150-0-150 transformer, you don't need a 4-diode bridge. Just ground the center tap ("0"), and use two rectifier diodes in a full-wave configuration. Connect the anode end of a rectifier to each of the 150 windings, and tie together the cathode ends (marked with a line). At that same point connect your CLC filter. Depending on several factors, you should get somewhere just over 200 volts. There are many references to power supply design if you do some searches.

If you are a newbie, I hope you will spend some time looking at the permanent high voltage safety thread here.

mark845 · 5th August 2006, 07:09 PM

Thank you. Yes, I did not think about a full wave rectifier circuit. I will try this because I have a 125 - 0 -125 VAC transformer already in the breadboard circuit. Actually, this voltage is on a very low end of circuits I have built.

sorenj07 · 6th August 2006, 02:31 AM

If you're working on building a PSU then I can't recommend Duncan Amplification's PSU Designer II software more. You have to make careful measurements of your PT, unloaded voltages, and (unplugged) impedances of all the windings, but once you do, it's great.

http://www.duncanamps.com/psud2/index.html

5th August 2006, 06:27 PM	#1
mark845 diyAudio Member Join Date: Jul 2006	Transformer Leg Connection Question Hello All, I am building a small tube amplifier where I need a B+ voltage after bridge rectification and CLC of 200 - 250 VAC. I cannot find a transformer manufacturer who makes a 75 - 0 - 75 VAC or single 150 VAC secondary. If I used a transformer with a 150 - 0 - 150 VAC secondary and only connected up one leg of the secondary, would there be any problems? Note that this transformer will also have a filament secondary.

5th August 2006, 06:45 PM	#2
Brian Beck diyAudio Member Join Date: Dec 2004 Location: South Florida, USA	With a 150-0-150 transformer, you don't need a 4-diode bridge. Just ground the center tap ("0"), and use two rectifier diodes in a full-wave configuration. Connect the anode end of a rectifier to each of the 150 windings, and tie together the cathode ends (marked with a line). At that same point connect your CLC filter. Depending on several factors, you should get somewhere just over 200 volts. There are many references to power supply design if you do some searches. If you are a newbie, I hope you will spend some time looking at the permanent high voltage safety thread here. __________________ Brian

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5th August 2006, 07:09 PM	#3
mark845 diyAudio Member Join Date: Jul 2006	Thank you. Yes, I did not think about a full wave rectifier circuit. I will try this because I have a 125 - 0 -125 VAC transformer already in the breadboard circuit. Actually, this voltage is on a very low end of circuits I have built.

6th August 2006, 02:31 AM	#4
sorenj07 diyAudio Member Join Date: May 2006	If you're working on building a PSU then I can't recommend Duncan Amplification's PSU Designer II software more. You have to make careful measurements of your PT, unloaded voltages, and (unplugged) impedances of all the windings, but once you do, it's great. http://www.duncanamps.com/psud2/index.html

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