CV-12 Stuck in Omni

[Mkvy83]

So recently I put a 251 circuit board, an rk-12 capsule, and a new tube in my cv 12. I also swapped out the diodes in the PSU -the orientations are correct. It sounds great, however it only operates in Omni, even when I change the polar knob on the PSU. I did a continuity test and voltage test and everything came back normal. I assume the capsule is fine, since it doesn’t have any frequency loss and voltage test came back normal for the wiring. Whenever I initiate the pad or HPF the mic clips, but I’m assuming that is probably a separate thing. The polar pattern knob worked fine before the knob and none of the wires were knocked loose. Has anyone dealt with this before or have any idea where to start?

Thanks

 

[radardoug]

It would be helpful if you put in more detail about the parts. What is a 251 circuit board? Where did you get the capsule?
Did you wire the capsule correctly? It would need to be at least a three wire capsule. Is it? Did you mix up the connections?
Have you measured any voltages?

 

[Mkvy83]

Sorry, I got the 251 circuit board and an rk-12 capsule from mic parts. I double checked the wiring and reworked some solder joints -everything is correct. The voltages come back correct 0v in cardiod,  55v and 115 v in omni at XLR3 on the board.

 

[RuudNL]

Check if there is continuity between the front and the rear membrane.

 

[Mkvy83]

I checked the continuity on all parts for the mic and everything came back good, how would I go about checking the continuity of both membranes? Thanks

 

[RuudNL]

Just measure the resistance between (the wires connected to) the front and rear membrane.
I once had a capsule that had an internal short circuit, causing it to function only in omni mode.

 

[Mkvy83]

I just tested the front and back pads to the capsule on the pcb like you said. Nothing even registered, didn’t make a sound -you might be right. In that case I’m assuming I would have to replace the capsule?

 

[RuudNL]

I would suggest (just to be sure) to remove the capsule out of the circuit and check again.
You can do so by unsoldering the wires connected to the front and rear membranes, and measure the resistance (again) between the wires connected to the membranes. If you measure a short circuit, I would contact MicParts and see if they are willing to replace the capsule.
Sometimes this happens (it seems), when the screws holding the two capsule halves together are not insulated inside the capsule and thus are (unintentionally) connecting the two tensioning rings that are in contact with the membranes together.