Shure T1 Body-Pack Transmitters
17
Bench Checks
25C1016 (CC)
Bench Checks
Dc Power
n Verify that 9 Vdc (±0.35 Vdc) is present at TP6. If this voltage is
low, trace the circuitry back to the power supply to see where the
loss occurs. Check:
S power switch
S bias on Q105
S L101
S circuit-board ground for 0 V
n If you have a short to ground from 9 V, try isolating different parts
of the circuit. Narrow it down to the
RF or audio section. Look for
foil shorts, solder bridges, and capacitors that have been
installed backwards.
n Check for 5 Vdc (±0.25 Vdc) at
TP7 (pin 7 of U101). If the correct
voltage is not present, check:
S pin 13 of U101 for 9 V
S values of R133, R135, and R137
Audio
All the steps in this section comprise a methodical way of determin-
ing where the audio signal is being interrupted:
n Check for audio at pin 7 of U102. If it is not present, check that
the dc bias at pins 5, 6, and 7 of U102 is `4.5 Vdc (half the lev-
el of the supply voltage). If the correct voltage is not present:
S Trace the circuitry: this bias derives from the 9 V line through
voltage divider R103 and R105, then through R106 to pin 5.
S Look for foil shorts, incorrect parts, and bad connections.
n If there is audio at pin 7 of U102 but not at pin 14, check the dc
bias at pins 12 and 13 (`1.8 Vdc) and pin 1 (`3.7 Vdc). If the
correct voltage is not present:
S Trace the circuitry: this dc bias proceeds from pin 9 of U101
through R107 to pin 12 of U102.
S Check (a) the parts in the feedback path from pin 14 to
pin 13, (b) the parts connected to pin 7, and (c) the connec-
tions from U102 to U101.
n Check the connections from pin 14 of U102 to the next stage, to
the limiter (Q103), and to pin 15 of U101.
