jsteiger said:
Would it be as simple as changing out R11, R21, R13 and R23 to match the values for the standard 16V parts of the circuit?
That, and you need to supply rather more cooling. As it is the 24V regulators have to drop ~3V more than the 16V ones; when rewired for 16V but still fed from a 24VAC winding they have to drop ~11V more.
From another perspective: if you take 24VAC in to get 16VDC out, your regulator has to dissipate about as much as your load. So for a fully-loaded 500 rack
each of the regulators has to dissipate ~23W, or ~46W for the pair. Not impossible, but not trivial for a TO-220 reg either.
EDIT: looked at the data sheet, and "not trivial" was a bit of an understatement. Max junction temperature for a LM350T is 125C, max junction-to-case thermal resistance is 4K/W. Dissipating 23W drops 92K over that, so even if you find an infinite heat sink at full load your ambient temperature cannot be higher than 33C. Good luck achieving that in a typical rack.
EDIT #2: Ah, I see you were talking about
"If someone has the proper toroidal trafo". I assumed that that would be the one Volker specced in the first post of this thread, but I suppose it could also mean a transformer with, say,
[email protected] plus a Phantom winding. While that does change the power dissipation issue, I would still opt for something simpler (like Keith's board).
jsteiger said:
Boy, the VPR spec of 5mA per channel is kind of a joke isn't it? I wonder what they were thinking?
Once upon a time, when the Phantom voltage was mainly used to bias the capsule, the P48 spec (DIN 45596) stated that 2mA was the maximum allowed current draw. I'd say the VPR folks were simply following
orders the standard.
JDB.
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