Question on Bridge Rectifer

dsundblom · 25th July 2007, 08:14 PM

Hi Everyone

This is my first post, I'm a newb here. I have been collecting and restoring tube radios for about 12 years. The last few months I've become very interested in tube audio. A friend built me a single ended tube amp and I built a preamp. Both turned out excellent. I have now started on a phono amp.

My question is about the bridge that I bought for my filament supply. I have 6.3 VAC from my transformer. I hooked up the bridge and have 16.6 VDC with no load or no filter cap. I'm puzzled, this can't be right, right?? Seems to be acting as a doubler.

Thanks in advance. Great forum.

David

KISS · 25th July 2007, 10:34 PM

You probably need a different lesson. Not all AC meters are the same. Most assume a sine wave input. A rectified signal clearly is not a sine wave.

Put your capacitor filter in there and a slight load and things may behave and be closer to 8 volts if I remember my PS design math.

One other thing to watch out for is that selenium rectifiers need to be simulated if you are duplicating earlier designs using this technology. They have a very high series resistance and thus a high voltage drop.

25th July 2007, 08:14 PM	#1
dsundblom diyAudio Member Join Date: Jul 2007	Question on Bridge Rectifer Hi Everyone This is my first post, I'm a newb here. I have been collecting and restoring tube radios for about 12 years. The last few months I've become very interested in tube audio. A friend built me a single ended tube amp and I built a preamp. Both turned out excellent. I have now started on a phono amp. My question is about the bridge that I bought for my filament supply. I have 6.3 VAC from my transformer. I hooked up the bridge and have 16.6 VDC with no load or no filter cap. I'm puzzled, this can't be right, right?? Seems to be acting as a doubler. Thanks in advance. Great forum. David

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25th July 2007, 10:34 PM	#2
KISS diyAudio Member Join Date: Jan 2007	You probably need a different lesson. Not all AC meters are the same. Most assume a sine wave input. A rectified signal clearly is not a sine wave. Put your capacitor filter in there and a slight load and things may behave and be closer to 8 volts if I remember my PS design math. One other thing to watch out for is that selenium rectifiers need to be simulated if you are duplicating earlier designs using this technology. They have a very high series resistance and thus a high voltage drop.

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