10-06-2024, 01:22 PM
(10-06-2024, 10:53 AM)Mike Watterson Wrote: I tried that and it's about -100V no load. Drops to about -60V on a 220K Ohms load. So I'll put it back as it was and regulate it with a diode to about 110 to 120V..
I also added a pair of 270K resistors in series as a load on the +700V approx, otherwise nasty! Centre tap was 356V! Eeek! The resistors are rated 200V. I'll move the 0V end to the +350 rail.
I put -HT rectifier connection as it was. Added 47 K series and a reversed 1N4148 (randomly chosen) across the 220K resistor that will be replaced by 220K linear pot. That gives a reasonable 96.5V. The 1N4148 are stupidly cheap and seem happy with < 1mA reverse current (that would be < 100 mW). The raw -HT fell to 176V.
The 220K is a load of 440 μA. The 176 - 96 = 80V, thus 47 K Ohms source gives 1.7 mA. That means 1700 - 440 gives about 1.3 mA = 120mW, so the 47 K Ohms is a bit low, or I could use a 100K pot, leaving about 800uA in the diode which is about 80mW, much better.
