bosoz psu ?? blown zeners ??

[dqswim]

help,

I setup my x- bosoz for the first time 2 days ago and I had a little buzzing and some nice hum. On checking my wiring both channels of my dual mono psu went to ~4v under load. The psu units checks out fine under no load but under load the output voltage goes close to zero.

Using what I have (a fluke rms volt meter) and the built in diode checker the zeners on the source of the output mosfets seem to be shot. (z115 and z116 in the circuit)

So does anyone know what could make those go, if this is truly my problem? I am eager to get this running after so long to collect all the parts. I also don't want to repeat mistakes if possible.

Thanks for any help of suggestions. It's amazing how Nelson strives to make these circuits as simple as possible and I still need to write on the "Purple Pages" for help.

-dave

[dqswim]

What is the difference between having a 9.1v zener from regulated V supply to the mosfet gate, as in the bosoz.

Vs, in the p1.7 there is a 50v 1a diode 1n4001 from gate to unregulated.

I have a bosoz with a c-r-c that has slighty more capacitance than the p1.7. Would I be better using ther didoe protection circuit used in the p1.7 due to the added capacitance or does it matter.

-dave