AZ1 voltage doubler
I have one power transformer secondary 125VAC not center tapped but I want to do a voltage doubler to get 250VAC, could I do an artificial center tap like attached schematic? the schematic resistor values are for power transformer for heaters and can be 100R 1/2W or 220R 1/4W, they will of course consume a little extra current from the transformer (32mA when using 100R resistors at 6.3V) so what resistor values and power to draw the minimum current?
N.B. Information taken from Valve Wizard site The Valve Wizard
TIA
Felipe
I have one power transformer secondary 125VAC not center tapped but I want to do a voltage doubler to get 250VAC, could I do an artificial center tap like attached schematic? the schematic resistor values are for power transformer for heaters and can be 100R 1/2W or 220R 1/4W, they will of course consume a little extra current from the transformer (32mA when using 100R resistors at 6.3V) so what resistor values and power to draw the minimum current?
N.B. Information taken from Valve Wizard site The Valve Wizard
TIA
Felipe
Attachments
Use this standard voltage doubler circuit. http://hyperphysics.phy-astr.gsu.edu/hbase/Electronic/ietron2/voldoub.gif
Voltage doublers work best with SS diodes. The reason is the large capacitance needed in the doubler stack. The setup is 2X 1/2 wave rectifiers back to back.
You can use vacuum diodes, but a large inductance and a large reservoir cap. have to follow the doubler stack.
The AZ1 is directly heated. You need 2 bottles and 2 CT filament windings. The plates are connected in parallel and the CTs provide the cathode connections.
You can use vacuum diodes, but a large inductance and a large reservoir cap. have to follow the doubler stack.
The AZ1 is directly heated. You need 2 bottles and 2 CT filament windings. The plates are connected in parallel and the CTs provide the cathode connections.
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In this case the cathodes cannot be connected together, as you can see from the schematic.
You could use two separate rectifier tubes, though. How much current do you need?
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Note that an auto-transformer generally will not provide isolation from the mains since they only have a single winding, and as such they should only be used in conjunction with an additional isolating transformer for safety.
I am still confused. Are we helping with an AC heater supply, DC heater supply or DC high voltage supply? Did the OP think that adding an artificial resistive centre-tap would somehow double the secondary voltage? What on earth has an autotransformer got to do with it?
What exactly is the OP trying to achieve? What exactly does he have to start with in the form of components, transformers etc.?
What exactly is the OP trying to achieve? What exactly does he have to start with in the form of components, transformers etc.?
The OP said he wanted to double the AC voltage (125 up to 250 VAC), and made the erroneous suggestion with the resistive centre-tap. An auto-transformer was suggested as a solution, but I felt that even if it was not the most suitable solution for the OP's needs, there should be a warning about the potential use of auto-transformers (since others might later pick up on the suggestion).
I agree, a much clearer picture of what the OP wants to achieve would be helpful.
I agree, a much clearer picture of what the OP wants to achieve would be helpful.
No for heater, I want to double the DC voltage after the AZ1 for B+, power transformer is 125VAC 100VA not CT. Attached pic how I use now the AZ1 hybrid Graetz with two diodes UF4007.
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A "full wave" doubler should have 2 identical diodes. A half wave "doubler" could be constructed from 1 SS and 1 vacuum diode. However, the ripple freq. in the resulting rail will be 1/2 of the AC mains freq. That places an additional burden on the remainder of the PSU filter.
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All you need is an AZ1 with two separate cathodes, or two AZ1.
Post 17 is not a voltage doubler. Some people might call it a voltage halver.
Forget about all you have seen and read about resistive CT for heater supplies. This is irrelevant to your current problem. You don't need a CT, and a pair of resistors don't really provide a CT anyway.
Post 17 is not a voltage doubler. Some people might call it a voltage halver.
Forget about all you have seen and read about resistive CT for heater supplies. This is irrelevant to your current problem. You don't need a CT, and a pair of resistors don't really provide a CT anyway.
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