I.E. should i aim for the zener to drop around 10v rather than using them to drop around 2v?
The load resistor drops the voltage not the zener, in a ideal world you would aim for the current through the zener to be about the same as the current in the load the zener is regulating the supply for. Though this is limited by the current the zener can stand, if its too high (as Mike said) you need to look at more complex regullators.
You need to calculate the current through the zener and load for the max and min voltage the supply will produce, and make sure it doesn't drop out of regulation.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
Yes you really want it dropping it by a reasonable amount, not just a tiny bit.
I am reminded of many years ago when I was still pretty green at this malarky, I made an integrated amp with a PSU that had a zener or two on the supply line just for the pre-amp stages. It always made 'hiss', do you think I could get to the bottom of it?
Turned out in the end the zener was right 'on the edge', that's where it was coming from!
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
Ill check my voltages later. With the 240v Tx voltages are a little low and with the 280v Tx there a little high. Ill measure both and see what works out best. With the 240v tx i may not have enough extra voltage to play with.
In theory, with enough voltage to drop 10v with the zener set up at V1, V2 and V3 will be running 10v too high.
Ill see if i can level it out so v1 is 5v too low and V2 and V3 are 5v too high. That should keep everything balanced as it should be (if that important, i dunno).
I guess i could go really crazy and actually spend out on a suitable mains Tx rather than pissing about with ancient, salvaged ones which arent quite right.
