GReg-Electrical Tech Journal

254
2/26/7
Problem-
Electrovoice PL-20 on my desk with the base loose and wires ripped.


Solution-
The bottom piece is held on with an end screw which I guess was a bit loose. Someone thought the base simply screwed back on, rotated the base ripping the wires off their points and bending an RF supressor post(?). Disassembled the base (removed XLR connector, unscrewed hex screw beneath, which held the bottom housing to the mic body), resoldered audio wires from XLR to mic o/p solder terminals, bent back the post, and put it back together.
I checked the polarity with a reference mic. All is good.


Designed panels for the stupid Digidesign buffer amp box, then ordered them.

Studer A820MCH Studio A- Replaced 100uF cap on the 3 Repro Preamp Boards
Greg Norman FG

GReg-Electrical Tech Journal

258
3/1/7
Calibrated tensions on the two Ampex ATR 2-tracks in studio A's control room.

Replaced the guts in the dead Senheiser 441. Once that was done, I felt free to crack open the broken one to see what was up with it. I found that there was a circuit board housed in the cylinder that is an eq network, their "brilliance" switch activates it. One of the wires to the switch got severed somehow, probably when it was dropped on its nose.
How?
The capsule and eq network are mounted with 2 spiral spring suspension mounts. They allow about a 1/2" worth of play, front to rear, and a tiny bit side to side. If this mic were dropped on its business end from shoulder height (looking at the damage to its frame, this appears to have happened), the capsule/eq assembly would have moved violently forward. The wires from that assembly are flexible but tiny, probably to allow the movement. They are soldered to the "brilliance" switch which is stationary, near the connector. The blue wire (severed wire) must have been tugged too much when the capsule/eq shot forward in the fall.
Either way, the thing is functional, and now we have a spare capsule/eq assembly for when someone rolls over another one with their SVT cab.
Here is the new assembly from Sennheiser-
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Here is the old one exploded-
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This is the "brilliance" eq board and the rear suspension mount-
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Here it is while I'm doing my listening test. The audio is taken off the non brilliant taps, and the jumper cable connects the shield to the case of the assembly. You can see one of the spiral/spring shock mounts pretty well here.
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Spring training games have started!
Greg Norman FG

GReg-Electrical Tech Journal

259
Some more shots of the shop from my camera phone.
This is the west wall with the 2nd tech desk and component trays-
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This is the North wall with shelves full of parts, broken gear, books, and manuals-
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This is the tower in the middle which has current repair/projects, wires of all sorts, some of my CDs, and Tim Midgett's macbook power supply-
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Greg Norman FG

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