I've been planning to replace the power transformer for the LV supply of my ART-13. The fellow who built it did something to the effect of combining the current transformer's 5v winding with the secondary of a 28vdc transformer to help boost the primary of the LV supply's transformer to help get the voltage up to around where it should be. The problem is that at 117vdc I'm just barely seeing 390vdc under load. This really isn't enough not to mention I'm sure the transformer isn't very pleased having so much being thrown into its primary winding.
I was thinking of replacing it with a toroid transformer such as this:
http://www.antekinc.com/details.php?p=90There's a spec sheet PDF on that page under "Files and Specs". It seems to sit at 470vdc unloaded and drops to 430vdc at 1.3A. Considering how the ART-13 needs about 300-400ma for its LV this should be plenty of current capacity. I also need to increase the voltage capacitor of the filter capacitor network for the LV network. Currently it looks to be a single 60mfd 450vdc capacitor. I recently purchased two 120mfd 420vdc capacitors to run in series.
Do you think I'll need an equalizing resistor for the two capacitors? Following this formula I get the following results for the resistor value:
For 2 capacitors in series: R = (2Vm - Vb) / (0.0015 C Vb)
where R = resistance in megohms
Vm = max voltage you'll permit on either capacitor
Vb = max voltage across the entire bank of two (or N) capacitors
N = number of caps in series
C = capacitance in microfarads
(2 (500) - 840) / (0.0015) * (120) * (840)
160/151.2 = 1.058201058201058
Does that seem right to you?