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Old 1st September 2010, 10:54 AM   #1
Brit01 is offline Brit01  United Kingdom
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Default Voltage doubler using PSUII?

Attempting to use PSUII to create a voltage doubler.

I have to 28V (3 amps each) trannies I will put in series and use a voltage doubler.

I calculate 28+28= 56 volts
56 *1.4 = 78.4

78.4 * 2 = 156 volts.

I cannot seem to get a simple circuit to work from 78.4 volts.
Maybe I'm expecting too much from the draw of 800 mA of current needed.
I tried using low resistors and high capacitance but the psuII drops negatively and gives me around 20 volts! What am I doing wrong?

Better to work it out manually?

Can I get 100-150 volts to supply 800 mA from these 2 trannies?

Maybe better to buy a new 110V tranny. But...$$$
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Old 1st September 2010, 12:21 PM   #2
piano3 is offline piano3  United Kingdom
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Hi, I'm not sure that putting transformers in series,rather than separate windings on the same one is recommended.
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Old 1st September 2010, 12:35 PM   #3
piano3 is offline piano3  United Kingdom
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If you want to get high voltage from 2 low volt secondary transformers then run the low voltage secondary of the 2nd one as a primary from the low voltage secondary of the first one. I often use transformers backwards without any problems so that I can get nearly 400V from an off the shelf control panel transformer. You can expect that the V out will not be quite as high as the V in. If you want to reduce it further then use a low value reservoir cap(a microfarad or so) so as not to waste power. Or, you could then use a doubler if you wanted.
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Old 1st September 2010, 12:46 PM   #4
Brit01 is offline Brit01  United Kingdom
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If you want to get high voltage from 2 low volt secondary transformers then run the low voltage secondary of the 2nd one as a primary from the low voltage secondary of the first one.
220/28- 28/220 = 220V.
How much loss would I expect?

Think I'll be looking for a used 220/110 step down tranny. These are common and supply high amps.

Great to run 6080 and 6AS7 @ 100mA with 100volts or so at the plate.
This would dissipate 1 watt of power no through a 100 ohm? So a 2 watt 100 ohm cathode resistor should be fine I think.

Looking to start my first OTL. Will start with 1 channel and a couple of tubes first.

Maybe a modified futterman with floating power supplies as used in the M-60. Not sure how I will implement it yet but ....

Last edited by Brit01; 1st September 2010 at 12:57 PM.
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Old 1st September 2010, 01:12 PM   #5
piano3 is offline piano3  United Kingdom
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The loss is a bit difficult to predict and I presume mainly comes about because of a resistive drop on a winding which is not usually a source.Ask one of the big guys;I find DF96 very helpful. If the transformer is high VA I would expect the problem to be less. Where exactly are you? You seem to have a great problems sourcing transformers!
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Old 1st September 2010, 01:25 PM   #6
Merlinb is offline Merlinb  United Kingdom
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I just tried it in PSUII without problems (see attached).

Using 470uF capacitors, at 800mA load current the DC voltage is 131V with 8Vp-p ripple. The ripple current in the transformer is 3Arms, which nicely matches your real transformers.
Attached Images
File Type: jpg Doubler.jpg (115.3 KB, 155 views)
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Old 1st September 2010, 01:26 PM   #7
Brit01 is offline Brit01  United Kingdom
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Yep I'm down in Uruguay.
I even get strange looks in the electronics shops when I ask for 400V caps!!
Have to source most of my parts from ebay. 80% get through customs in small packets.

There are some locals that make power transformers but at ridiculous prices and I and dubious about their amperage ratings.

There are some good power rated step down trannies made for playstations etc.

I see in the atmosphere M-60 power supply they use a 50+50 tranny with RCCCCC set up for the floating supplies. 1 x 1ohm resistor and a series of high value capacitors in parallel following but unfortunately PSUII does not allow me to do this. 'Illegal operation" it says.
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Old 1st September 2010, 01:42 PM   #8
piano3 is offline piano3  United Kingdom
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Uruguay! Goodness,that really is exotic. Must be fun though!
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Old 1st September 2010, 02:00 PM   #9
Brit01 is offline Brit01  United Kingdom
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Goodness,that really is exotic
Lol. Not quite. Don't imagine Brazil!
It's way down south.

Some palm trees around but with British like winters!!

Quote:
Must be fun though!
And boring. Nothing to do here. (but build valve amps!)

Last edited by Brit01; 1st September 2010 at 02:05 PM.
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Old 1st September 2010, 03:40 PM   #10
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#1 I have to emphatically disagree with piano3: it is far preferable to use 2 identical transformers with secondaries in series than to do a back-to-back with those same identical transformers. Back-to-back is best done with dissimilar transformers, so that the larger one can handle the extra magnetizing current.

#2 Using a 3A rated transformer with a doubler and expecting only 800mA is quite reasonable. As for why it isn't working in PSUDII; have you really gone over all the settings you have in PSUDII? Are you focusing on the start up transient too much? Maybe we should be focusing on that?
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Last edited by leadbelly; 1st September 2010 at 03:44 PM.
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