I recently came into a few old EV PL76 mics. These were a small diaphragm condenser that used some weird mercury laden battery or something back in the day which are difficult to come by these days. EV eventually made the PL77 which could be used with or without the battery, using phantom power as a source instead. Looking at the schematics, which were unusually easy to find, i noticed that the only difference was 4 components which were not in the signal path that dealt w the power. Taking the same idea and swapping a regular diode for a zener, (all I had laying around) i was able to make a tiny board to fit these components onto which fits neatly into the old battery compartment. One end connects to the xlr via the convenient little slot EV left at the bottom of the compartment, and the other simply connects to the + battery terminal. This basically turns the 76 into the 77.
Left the wires on the long side inside the compartment so you can pull the xlr if needed for service. The board is double sided but all traces are on one side. The wires form a raft the board sits on so it doesnt ground out but the tape inside could already do that.
Seems to work and these mics dont sound bad.
I printed up a bunch of these boards if anyone wants to breathe life back into one of these old mics, hit me up. Should be able to send in a small envelope.
Components:
2 6.81k .1% resistors
1 5.6v zener
1 25uf 25v electrolytic (polarized) axial
4 pc wire
Left the wires on the long side inside the compartment so you can pull the xlr if needed for service. The board is double sided but all traces are on one side. The wires form a raft the board sits on so it doesnt ground out but the tape inside could already do that.
Seems to work and these mics dont sound bad.
I printed up a bunch of these boards if anyone wants to breathe life back into one of these old mics, hit me up. Should be able to send in a small envelope.
Components:
2 6.81k .1% resistors
1 5.6v zener
1 25uf 25v electrolytic (polarized) axial
4 pc wire
Attachments
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