Help with Phantom power

Hi All,
Just finished wiring up my new mic pre (API-ish), but when I plug in a condensor mic and turn on the phantom power, the voltage immediately starts to drop from about 46 volts to less than 20 volts in about 5 seconds. aNY HELP APPRECIATED.
tHANKS,
fREDDY g

> when I plug in a condensor mic and turn on the phantom power, the voltage immediately starts to drop from about 46 volts to less than 20 volts in about 5 seconds.

The voltage on the XLR-jack pins -should- go down to 10V-30V when the mike is powered-up. There is 3K4 resistance between the 48V supply and the XLR-jack pins. If the mike draws 8mA, 3K4*8mA= 27.2V drop from the +48V supply to the mike, so 48V-27.2V= 20.8V from pins to ground. Phantom mikes are allowed to draw zero to 15mA, so the exact voltage will vary depending on the mike.

If you are measuring, not at the XLR pins but at the "+48V" supply, and it is dropping, then you have a weak 48V supply.

Man, we get a phantom question every day it seems. Does this justify a META-Phantom Power thread and are there any people interested in running it?
A bunch of different phantom schematics, with maybe an old Nuemann or two might be worthwhile.
DC to DC, straight up single rectifier/pi filter supply, sophisicated regulated supply, short proff supply,.you get my drift?
If that is too specialized, we could do a power supply meta instead.
:guinness:

Thanks PRR, I'll go over it again...
CJ, that's a great idea!
Freddy G