Quote Originally Posted by UV101 View Post
One final thing. My 18v TX is giving me about 28v when rectified. I ususally work on 1.4 x TX voltage but it seem this is incorrect. Can anyone shed any light for me please. The reason I ask is that my caps are 35v and I think I will se more than 35v DC on them using a 25vac TX.
You have the voltage drop from the diodes to take into account but most of all you have the "regulation" of the TX to add on. Small TXs can have a regulation factor of 15% or more so if you have a light load on such a TX you can be adding close to 15% to your TX output volts. Possibly I've over-simplified a touch but this is near enough.

A higher rated TX will have better regulation, you can check this in the TX specs. A very high VA TX will give you much closer to 25V but possibly more like 27V AC or 34V DC after the diodes (depending on diode type).