"Fox 460" Mic Kit - Need Help! XLR Pin 1 Continuity

briandye

New member
A coworker of mine asked me to "build" this mic for him, its a "Badaax T-11A" with the "Fox 460"

Everything went really smooth and well, I followed the directions word for word. Kept all joints clean, no frays in the wires, etc.

The last steps before putting the tube back in say to check for continuity between a few pins and joints, all was well. The last 3 steps are to check that theres NO continuity between 3 places. All is well besides ONE.

The XLR Pin #1 has continuity with the mic chassis. I have totally taken the mic back apart and cannot find anywhere it would be shorting out. Nothing from the board is making contact with the chassis besides the screws to hold them in. (When I touch one lead of my DMM to the chassis, and the other lead to Pin 1, I get an Ohm readout, instead of just displaying "OL" like its supposed to)

Im stumped here, and he was hoping to have it back today, and I thought it would be no problem, but ive been stuck for an hour now.


Thanks for any help!
 
I'm no tech but it seems to me that continuity from chassis to ground would make the chassis a shield. Maybe it's supposed to do that.

Are there conductive pads around the mounting screw holes? Could you pull the board and check continuity from pin 1 to a mounting screw when it's out of the chassis? Does the resistance vary or is it constant?
 
Below is a schematic for an APEX 460 (couldn't find one for the Badaax T-11A). Pin 1 might read up around 540kohm in the APEX through R4(270kohm) and R3(270kohm). What value of ohms did you measure and did it start at a low value and climb (capacitor charging)? If a schematic was supplied with the Fox mod, is it connected similarly to what is shown in the APEX? Kinda hard to troubleshoot without a schematic of sorts.

apex460_mic_lg.jpg
 
I'm no tech but it seems to me that continuity from chassis to ground would make the chassis a shield. Maybe it's supposed to do that.

Are there conductive pads around the mounting screw holes? Could you pull the board and check continuity from pin 1 to a mounting screw when it's out of the chassis? Does the resistance vary or is it constant?

There are conductive pads around all 4 mounting screws on both boards. I will check that continuity when I get home.

Below is a schematic for an APEX 460 (couldn't find one for the Badaax T-11A). Pin 1 might read up around 540kohm in the APEX through R4(270kohm) and R3(270kohm). What value of ohms did you measure and did it start at a low value and climb (capacitor charging)? If a schematic was supplied with the Fox mod, is it connected similarly to what is shown in the APEX? Kinda hard to troubleshoot without a schematic of sorts.
View attachment 97860

Yeah, Pin 1 seems to start low, and then rises up to ".535-.540" on my DMM and stays there. There is a schematic on the back of the book. I will attach it later on when I can get to it. Ill be honest though, I haven't really worked on electronics to this extent, I was just following the books directions step by step. The soldering/connecting everything where it needed to go was easy. All tests verified proper wiring up until this point. Only thing it had me test that "failed."
 
Yeah, Pin 1 seems to start low, and then rises up to ".535-.540" on my DMM and stays there. There is a schematic on the back of the book. I will attach it later on when I can get to it. Ill be honest though, I haven't really worked on electronics to this extent, I was just following the books directions step by step. The soldering/connecting everything where it needed to go was easy. All tests verified proper wiring up until this point. Only thing it had me test that "failed."
Yep, that's what acaxis said. 0.54M = 540K. It starts low and rises as the cap charges. Something pretty much has to connect those ground points to the chassis exactly for shielding purposes as bsg said.
 
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