I know this is a dangerous practice, but obtaining a transformer to make a vacuum tube power supply in my country is prohibitively expensive. So i have to go for transformer less psu. I am just making a very simple TUBE tester to check if the grid voltage is really controlling the plate current. Now this requires both + and - power supply. I should be able to completely cutoff plate current by making grid negative. I am presenting my design of power supply. Have anybody designed something similar? Correct me if some flaw in my design.enter image description here

  • \$\begingroup\$ I think you swapped the +96V and the -96V. How much current do you expect to get out of this? \$\endgroup\$ – Elliot Alderson Apr 18 at 18:00
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    \$\begingroup\$ Transformers aren't hard to come by, go find an old product and rip one out of an old unit. It might be more difficult to find 1:1 or the like but probably worth it \$\endgroup\$ – laptop2d Apr 18 at 18:08
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    \$\begingroup\$ The X-type capacitor is designed to fail short. I don't think you would want that behavior, placed as it is. Perhaps a Y2 here? \$\endgroup\$ – jonk Apr 18 at 18:09
  • \$\begingroup\$ Yes, X class should go between live and neutral. Shouldn't a Y class go between Live and Ground? \$\endgroup\$ – Greenonline Apr 18 at 18:13
  • \$\begingroup\$ I have corrected the +/- markings now thanks for pointing out. I capacitor fails short the the 100mA fuse should save me from fire. Correct me if i am wrong. Ok I will place one Y cap between line and ground. \$\endgroup\$ – user2544991 Apr 19 at 2:25

Your bridges have the diodes swapped compared to the +/- markings.

The bridges short out the capacitively coupled voltage. Try it with four 2uF capacitors rather than a single 1uF.

  • \$\begingroup\$ Hi thanks for reply. Can you please elaborate how bridges short out the capacitively coupled voltage. I need to go deep onto this. Which 1 uF capacitor you are referring to? This circuit do not have any 1 uF capacitor. Please elaborate \$\endgroup\$ – user2544991 Apr 19 at 2:27
  • \$\begingroup\$ I have corrected the markings. Thanks for pointing out. \$\endgroup\$ – user2544991 Apr 19 at 2:28
  • \$\begingroup\$ I see two 0.47uF caps in parallel so about 1uF, right? Follow the current paths through all the diodes. \$\endgroup\$ – Spehro Pefhany Apr 19 at 2:31
  • \$\begingroup\$ Thanks a lot. I followed the current path in the bridges and can see what you meant. It shorts out the line. This design have fundamental problem. Can anybody suggest a dual ended transformer less PSU with current capacity approx 5 mA max. 5mA is enough for my application. Output voltage can be anything from 100 v to 300 v. Again thanks a lot for your support and guidance. \$\endgroup\$ – user2544991 Apr 19 at 3:31

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