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Installation of FT817 RF Speech Clipper into Yaesu's MH-31 Standard Microphone
by Tony Wallace VE3TNW email@example.com
Schematic and more pictures click here
There have been some inquiries that have lead me to write more detailed installation instructions for the MH-31 "stock" mic installation procedure. In fact, one step is shown incorrectly in the schematics. Not that it does any harm, but, it does defeat VOX operation. (see step 10, below)
1. Remove the microphone cable from microphone.
2. Remove three Phillips head screws from back of microphone, including the one holding the microphone hanger flange. Remove the back part of the microphone.
NB: Directions are given with respect to the circuit board as seen facing foil side and the connector at the bottom.
3. Desolder the white (top) and brown (bottom) microphone wires from the circuit board.
4. Remove three small Phillips head screws holding the microphone circuit board to the microphone case.
5. Remove microphone cartridge.
6. Position Clipper board in space used by old microphone button. Position it with the new mic element in the microphone grille trough and the single white potentiometer facing to the left.
7. Return the microphone circuit board to the microphone case, securing it with the three small Philips head screws.
***You need to be aware of the potential to pinch wires and components here. Gently try it and make sure you're not trapping something where it shouldn't be. I found that the rubber cover for the up/down/fast switches needed to be firmly seated onto the cct board by pulling on the little "nubs" that fit through the holes in the board before it would cooperate. Also pay particular attention that the white wire is routed out of the way of the case screw posts as the cover makes space pretty tight in that area. It's a snug fit all around, but, shouldn't need forcing.***
8. Route the white wire under the microphone circuit board and solder it to the second pin from the left on the bottom row of connector pins. Trim off the tip of the wire that extends beyond the pin. Have a look to the drawings.
9. Route the drilled cable with the red wire up through the large hole in the middle of the microphone circuit board. Solder the black to the pin where the brown microphone wire was connected, the lower of the two microphone connections. Solder the red wire to the pin where the (old) white microphone wire was connected, the upper of the two.
10. This step is no more
11. Replace the back part of the microphone. Check and recheck clearances!! (see *** in step 7),. Then, secure it with the three Phillips head screws.
12. Replace the microphone cable.
TNX to VE3AYR, Hugh for original pix.
73 de VE3TNW, Tony
email aktualisiert 13. August 2009