Service manual

Shure LX2 Hand-Held Transmitter
14
Service Procedures
25D1006 (CG)
Service Procedures
Measurement Reference
dBu is a measure of voltage, and dBm is a measure of power.
For example, the HP8903 should be labeled dBu instead of dBm
because it is a voltage measurement. These two terms are often used
interchangeably even though they have different meanings.
Audio levels in dBu are marked as dBm on the HP8903.
dB Conversion Chart
0 dBV = 2.2 dBu
0 dBu = 0 dBm, assuming the load = 600 Ω
Test Equipment
Most test equipment needed is described in the Shure Wireless
Service Equipment Manual. The following test equipment (or approved
equivalent) is also needed.
Table 1
Test Equipment
Equipment Type Model
Audio analyzer *Hewlett-Packard 8903B
Digital multimeter Fluke 87
Cable PT1843
Frequency counter Hewlett-Packard 53181A
Rf signal generator Hewlett-Packard 8656B
Spectrum analyzer Hewlett-Packard 8590L
Shure LX4 receiver Shure LX4
Audio test head adapter ring PT1838Y
Audio Test Head PT1840
*Audio levels in dBu are marked as dBm on the HP8903B.
Changing the Frequency
System Operating Frequencies
The LX2 Hand-Held Transmitter printed circuit board (pcb) is marked
with a group letter that identifies the range of frequencies it can operate
within.
The operating frequency may be changed to a different frequency
within the same group. Before changing the operating frequency, refer
to the Functional Test section and check the transmitter for proper
operation.