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Old 14th August 2013, 08:08 PM   #1
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Default Someone Told Me This Wouldn't Work?

Hey anyone,
Someone told me this bias supply wouldn't work. Something to do with the secondary center tap? First are they correct? And if they are correct can anyone tell me why?
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Old 14th August 2013, 08:17 PM   #2
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There is only one lead connected to your transformer, thus current cannot flow.
You'll figure it out
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Old 14th August 2013, 08:47 PM   #3
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First, its a bias supply so I don't need current. And second, everything to the left of the 80 volt input is the original circuit. All I want it to do is bleed off the positive voltage to ground to keep the DC out of the transformer.
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Old 14th August 2013, 08:54 PM   #4
dfy is offline dfy
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Surely one of the leads on the secondary is connected to ground (probably via what you call the original circuit)?
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Old 14th August 2013, 09:07 PM   #5
DF96 is offline DF96  England
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Quote:
Originally Posted by mr2racer
All I want it to do is bleed off the positive voltage to ground to keep the DC out of the transformer.
If you are saying what I think you are saying then this is unnecessary. DC in a transformer winding is only a problem when it is unbalanced by DC in another winding. Half-wave rectification of a secondary is fine. Applying DC to a transformer is a bad idea. Taking DC from a transformer is fine, as the primary will balance it away. The result will be a little DC on your mains supply, but a bias supply will not create a problem.
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Old 14th August 2013, 09:10 PM   #6
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The transformer secondary center tap is connected to ground. The negative bias supply is connected to the output tube grids. And the positive 'waste' is connected to ground. When I say to the left of the 80 volt input I mean the left hand diode and to the left of it. That is the original circuit.
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Old 14th August 2013, 09:14 PM   #7
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Thanks Dave. On another thread someone told me, and it was seconded, that a half wave rectifier was a bad idea even for the bias supply. So maybe I'll just leave it the way Dynaco designed it then.
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Old 14th August 2013, 09:24 PM   #8
DF96 is offline DF96  England
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It is very likely that someone will pop up here disagreeing. I have had this argument before!
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Old 14th August 2013, 09:46 PM   #9
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In that case I side with you and Dynaco! But as drawn would the circuit work?
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Old 15th August 2013, 03:32 PM   #10
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Of course it'll work but it also will change nothing. What is your intention? To present the transformer with a more balanced load? Then you must also add a capacitor. At these power levels (few milliwatts) this is an exercise in futility.
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