Sennheiser MKH 20 Service Manual page 10

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Circuit test MKH60/MKH70:
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Operating voltage microphone:
Check voltages between R20 or R21 and ground; desired value = +41V;
both voltages have to be identical.
If the no-load voltage of the phantom supply device is not 48V, the deviation
from the desired value has to be identical.
·
Current consumption microphone:
Check voltages via R18 and R19; desired value in each case = 2.2V
(corresponds to 1mA in each case);
both voltages have to be identical.
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Balancing:
Check the voltage between the measuring points A(+) and B(-);
desired value = 0V
If the value is not 0V, rotate the coil core of L1 until the voltage is 0V.
¿
Operating voltage output stage:
Check voltage via D4; desired value = 4.5V
Check voltage via D5; desired value = 4.5V
´
Operating voltage oscillator:
Check voltage via C10; desired value = +30.5V
MKH 20...70
04/2005