In Reply to: reducing heater voltage - one resister or two? posted by eedork on March 24, 2007 at 20:40:29:
Hi.For AC heater decimal voltage trimming, sometimes it is hard to get resistors of the right resistance (plus tolerance %) to do the job precisely.
That's what I did & it works fine ever since. I would DIY wind 2 small inductors, with a few feet of magnet wires of SAME length & SAME size, say #18, BIfilar run, on a small non-ferrous core (say wood or plastic).
The leads of one inductor coil hooked up to in series of one leg of the heater PS circuit. Try to install this small inductor former closest to the tube heater socket lugs. Make sure to trim the lengths of the magnet wire of each coil to obtain the exact voltage drop you need.
The way both coils are hooked up is like a common mode noise suppressor. With a 0.1uF polyester AC bleeder cap across the O/P legs of the coils into the heater circuit, it forms a common mode suppressor while serving as a micro voltage dropper.
Here you will kill two birds with one stone.
c-J
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Follow Ups
- Why not use inductors instead of resistors? - cheap-Jack 11:47:33 03/26/07 (2)
- just be aware... - Dave Cigna 15:47:36 03/26/07 (1)
- Good concern ! - cheap-Jack 09:19:26 03/27/07 (0)