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[SignificanceNo3211]

I have a late 70's U87 that on occasion sends no output signal. I looked inside it to see if anything looked obviously off and noticed that the middle pin of the black transistor is not actually soldered to the terminal above (circled in the attached pictured.) It seems when the microphone head is straight the transistor's pin makes connection with the terminal by simply touching it, but as mentioned they aren't soldered together. Is this normal for the circuit?

Also, are you taking on any new customers, Klaus? If so, I think I'd like to send this mic over for inspection and capsule cleaning.

[Kai]

This is the gate pin of the input FET, and should of course be soldered to the connection it points to.

When fixing it:
• Try without any extra flux / solder, to avoid contamination.
• Don’t overheat the FET, solder time max 5s, or use a little measurement clamp on the pin to drain heat away from the FET.
• Take care for electrostatic discharging when fixing it.

[SignificanceNo3211]

Thanks for those instructions, Kai. I had thought maybe it was some strange relief mechanism (as the mounting plate had a bit of give to it.) I gather now that it's not supposed to move that much so I tightened the two screws on the mounting plate a little and then soldered the 3rd FET pin as you mentioned. Signal seems reliable on my first test -- I'll report back if there's any updates.