Quote Originally Posted by Iwant1 View Post
How accurate are the secondaries in a transformer? I'm asking to see if there will be any premature failure if they are not equal, from one coil working harder than the other.
That's precisely the reason I said '24V or 25V transformer (preferable)' in the previous post. Wondered if someone would pick up on that :)
If they're not equal then more current will flow in the secondary windings, but I don't think it's likely to be a big enough difference to cause failure.

Quote Originally Posted by Iwant1 View Post
I will be using pm752 drivers which I've had lying around for 2 years. Their datasheet says typical voltage is 48v and max voltage is 75v. In another post I read Gary saying to Jonathan that 72v from a toroidal supply is bit on the high side for the pm-752 driver. When I do the calculation 50 X √2 I get 70.7v. Is this the output I will be getting or are there other factors which bring it down by a few volts

I remember that one, to which I replied saying I'd checked the actual voltage at the MOSFETs and the spikes on switching were well below their rated 100V so I was happy to do it. That was with a 25+25V transformer from rapid, with the same PM752 drives from Zapp.
70.7V is correct, but the diode will drop about 1.1V, so more like 69.6V. However the mains voltage does have a fairly wide tolerance. It looks like those transformers output 50V with 230V on the primary, however the mains voltage could be 240V (depends on numerous factors). That would make the output voltage 240/230*50*√2=72.7V... still less than mine which has been fine for a long time now. You could always add a couple of turns of thick wire out of phase to reduce the output voltage, but crude but it works...