phantom pwer problem

[kassonica]

Hi all. I have a Great River ME-1NV mic pre and the phantom power is not working and was wondering if you guys had any idea's on how to fix it.
Everything else works fine.
Thanks

Kassonica

[Chris H]

How long has it not been working? First thing if you havn't already done so is to try a different mic lead then a different mic.

[kassonica]

yea thanks for reply, i have done all of the above it is something in the pre,

[chris p]

Hey kassie

Phantom power is not that special

+48V DC goes to a switch, with the pole of the switch going three places:

* (assuming pin 2 hot) pin 2 of the mic input via a resister in series (say 6k8);
* pin 3 of the mic input via a resister in series; and
* ground via a capacitor (eg 470uF electrolytic).


So working backwards
(1) when switched on, do you get +48V across pin 2 to pin 1?
(2) how about pin 3 to pin 1?
(if yes to both, the preamp is fine, the problem is elsewhere)

(3) do you have +48V at one side of the switch (compared to your 0V on the power supply)? if no, your power supply is the prob.

(4) when switched on, do you have +48 at both sides of the switch(compared to your 0V on the power supply)? If no, your switch is the prob.

(5) Failing that, test the resistors and replace the capacitor.

(6) Failing that, you've got bigger probs than can be fixed by me at least.

Good luck and I trust your outside the warranty period! Without being patronising, please be careful with the lid off and the power switched on. Usual cautions about messing around with 240V.

[kassonica]

Hey chris thanks heaps for your reply i will test what u have given me and falling that i'll be contact.

thanks again

mark