Shure UC2, Руководство по обслуживанию

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Shure UC2 Hand-Held UHF Transmitter
Bench Checks 25 25A1044 (RI)
Bench Checks
Dc Problems
Make all dc measurements with respect to the rf ground unless
otherwise specified. Connect the rf and audio printed circuit boards
together via the 11 pin connector, the battery contacts, and the “D” board.
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Make sure the battery voltage is between 6 and 9 Vdc. Make
sure TP+9 has this voltage. Check for the correct Vcc and +5 V
rf at Q301.
If incorrect voltage is present:
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Trace the dc back to the voltage regulator.
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Check the biasing resistor values around Q301.
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Check the power switch.
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Look for open coils, cracked parts, reversed polarity capacitors,
or solder shorts. If there is a short to ground from 5 V, try to
isolate different parts of the circuit.
Make sure that:
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The rf OFF signal changes from +5 Vdc at power up and power
down to 0 Vdc during normal operation. Trace the signal to the
microprocessor. Q301 should be saturated during normal
operation.
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Battery voltage appears at TP+9, U311, pin 6. Check for
reversed polarity capacitors, C308 and C309. Check for open
coil, L300.
Rf Problems
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If the carrier is out of specification by less than 40 kHz and can-
not be corrected by adjusting C314, put the transmitter on the
operating frequency (see Table 2). Measure and adjust the dc
voltage at TP30. (See Table 2 for frequency variations.) If the
carrier still cannot be trimmed properly, then check C314, C313,
and Y302. If they are correct, replace the synthesizer.
If the carrier frequency is not in the correct frequency range shown in
Table 2, or is unstable, the loop is unlocked.
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Check dc voltage at TP30. If it is 0 V or +5 V, look for a short.
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Check the solder connections at the contact board, VCO, micro
processor (traces LE, D, and CK), and synthesizer U304. If the
connections are good and there is no 4.0 MHz oscillation at
U304, pins 1 and 2, replace the crystal, Y302.
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Check the values and polarity of the loop filter: R316, C319,
R317, C353, R318, C320, C354, U306B, R319, R320, and
R321. Check the bias voltage of U304, pins 3 and 4, and
U306B, pin 8. As a last resort, replace the synthesizer, U304.