Listening Test; Functional Tests - Shure U4D Service Manual

Listening Test

Functional Tests

Preliminary Tests
Shure U4D Dual Diversity UHF Receiver
Before completely disassembling the receiver, operate it to determine
whether it is functioning normally and try duplicating the reported malfunc-
tion. Refer to the User Guide for operating instructions, troubleshooting
suggestions, and specifications.
Review any customer complaint or request, and focus the listening test
on any reported problem. The following, more extensive, functional tests
require partial disassembly.
Refer to the Disassembly section to partially disassemble the receiver
for the following functional tests.
Use dc blocks at all rf output to protect test equipment.
To reduce the risk of electrical shock, do not touch or short any
components in the power supply partition of the receiver. The heat
sink of the switching power supply and all ac wiring contain hazardous
voltages.
1. Remove five screws and washers from the top of the receiver
and two screws and washers from the left and right sides of the
receiver. Lift off the top cover.
2. Program the receiver squelch through the SET SQCH menu
to –10.0.
3. Program the receiver frequency through the SET FREQ menu to
any clean frequency in your area. To do this, select an inactive
television channel and then scan for a frequency at which the
yellow LEDs (RF A/RF B) are not lit. Note this frequency as Fo .
4. Connect a dc voltmeter to the center conductor (+) and the
ground (–) of BNC antenna channel A input, marked ANTENNA
A IN. The measured voltage should be to be ± 12.0 0.5 Vdc.
5. Set the rf signal generator frequency to Fo. Set the Level to
–90 dBm and set the deviation as follows:
UA, UB, MA, MB, MC, MD: 45 kHz deviation at 1 kHz modulation
6. Connect the rf signal generator to the BNC antenna channel
A input, marked ANTENNA A IN. Be sure to use a dc block to
protect the test equipment.
7. Rotate the receiver Output Level control to a fully clockwise
position.
11
KK: 40 kHz deviation at 1 kHz modulation
II: 28 kHz deviation at 1 kHz modulation
25D1062 (AG)