Voltage doubler using PSUII?

[Brit01]

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...$$$

[piano3]

Hi, I'm not sure that putting transformers in series,rather than separate windings on the same one is recommended.

[piano3]

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.

[Brit01]

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 ....

[piano3]

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!

[Merlinb]

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.

[Brit01]

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.

[piano3]

Uruguay! Goodness,that really is exotic. Must be fun though!

[Brit01]

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!!

Must be fun though!

And boring. Nothing to do here. (but build valve amps!)

[leadbelly]

#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?