G7 voltages spot on, distorted signal-damaged capsule?

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imo

Well-known member
Joined
Jan 19, 2006
Messages
397
Location
vashon, wa
I thought i was wrapping this up, all voltages were on, and i was having some pretty heavy distortion only on figure 8 mode, the other two sounded great. I was trying to chase it down, replaced the 10n cap between the two plates, and then found all patterns making the same distorted sound, the signal faintly heard behind high wall of distorted white noise. I have tried 3 different tubes with the same results, i have cleaned all high impedance areas pretty thoroughly. I am using one of Max's mic bodies and the noise is heard with the mic in the housing. The mic itself is grounded and i have the heater 0v tied to the Ov at the mic
I am using one of Dale's capsules, which has a front and back connection. This being my first microphone, i originally tried soldering directly to the center brass strip before it dawned on me that i could solder to the brass clamp that held the capsule. Could i have damaged it this way? I don't think any solder or flux made it on the capsule itself.
Here are some measurements if they point to anything:
158v on pin 2(B+)
148v after 10k on B+
67.5v on plated of tube (after 100k)
1.5v on cathode
72.8v between the 2 470k's i am assuming this will be on the center terminal as well
79.4 on the supply side of the 33m(in cardoid mode)

Are there any glaring points jumping out? Any way to check the capsule itself to see if it isn't working? I appreciate any points or direction
Many thanks
Ian
 
i have made some progress. The earlier distortion i think was caused by grounding the heaters to the 0v twice. The distortion is now down to a constant beating sound, like 32nd notes, that increase when i tap the mic. I have tried putting foam around the tube to see if it was transferring through the mic housing, but that made little difference. This happens on all polarity settings, though seems to be the loudest on omni and figure 8. Again, any ideas would be wonderful.
thanks
Ian
 

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