Tube DIY Asylum

RE: Using a CL inrush current limiter to lower B+

69.141.96.215

Eli Duttman

A

In Reply to: RE: Using a CL inrush current limiter to lower B+ posted by DAK on August 29, 2017 at 09:42:12

The other posters have given you reasonable options. A cLC filter, with a hefty inductor, allows you to tweak the small 1st cap. to get the rail voltage "just right". Bucking the power trafo primary is also good, provided no filament windings are present.

A 3rd possibility is switching to hybrid bridge rectification, to take advantage of the large forward drop vacuum rectifiers exhibit. Remember, the forward drop of a 5R4, at the rated 250 mA., is a whopping 67 V.

Eli D.

Follow Ups:

I have already tried the cLC and hybrid options - DAK 09:31:08 08/30/17 (4)
The voltage drop was too much. I have an extra 5v winding now that i dispensed with the tube rectifier. How do i use that in series or bucking the ac primary?
- RE: I have already tried the cLC and hybrid options - Eli Duttman 14:55:20 08/30/17 (3)
  Wire the "extra" 5 V. winding in series with the primary and measure. One configuration raises the rectifier winding's voltage, while the 2nd configuration lowers said voltage. You want the reduced voltage configuration.
  
  Eli D.
  - Just to be sure.... - DAK 15:22:56 08/30/17 (2)
    If the primary is 1, 2 and the 5v is 3, 4 . I connect 1 and 3 and 2 and 4 and measure the B+ at the secondary. If that is not lower than without the 5v winding connected then i reverse the order of the connections?
    - RE: Just to be sure.... - Eli Duttman 16:18:27 08/30/17 (1)
      Wire in series, not in parallel. Try 2 to 3 and apply "120" VAC to 1 and 4. If the rectifier winding measures higher, connect 2 to 4 and apply the mains voltage to 1 and 3.
      
      Eli D.
      - Ok, gotcha, thanx! nt - DAK 17:31:29 08/30/17 (0)
        
        In Reply to: RE: Just to be sure.... posted by Eli Duttman on August 30, 2017 at 16:18:27
        
        .

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