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4.1
SECTION 4 - MAINTENANCE
TROUBLESHOOTING
When troubleshooting, it wi II be necessary to make voltage measurements. These are
given on the schematic diagrams of the various amplifiers. It is recommended that,
after the console is insta lied and operating sati sfactori Iy, these readings shou Id be
checked and recorded on the schematic. This wi II provide the station engineer with
0
record of the actual voltage readings in his installation, using his meter. If trouble
later developes, he will then be better able to judge whether or not a porticu lor c ir-
cuit is operating properly since he wiil have available a record of the various readings
of his particular equipment. DC readings were taken with a 20,000 ohm/voltmeter as
indi cated on the schematic. RMS signal voltages are shown in parenthesi s and must
be measured with a vacuum tube voltmeter.
If
a VTVM is used to measure DC voltages,
slightly higher readings may be obtained.
TROUBLESHOOTING GUIDE
1.
No indication on either or both of the VU meters and the monitors on Iy operate
from the audition channel and the external input.
a. Interchange the program ampl ifiers with monitor ampl ifiers.
b. Check for 30 volts between terminal s #3 and #5 of the booster board and ter-
mina I s #3 and
119
of the output
boar~.
2. No signal on either or both of the program output lines, but indication on the VU
meters.
a. Check external cable connections on TB2.
b. Check S18 and output pad board.
3. No signal can be heard from any of the nlon itor speakers but the program channe I s
operate O.K.
a. Interchange the monitor amplifiers with the program amplifiers.
b. Check for 30 volts between terminals 113 and 115 of the booster board and 43
volts between terminal s
n3
and
1t9
of the output board.
4. No signal can be heard from the cue speaker.
a. Interchange the cue amplifier with either the program or monitor amplifier.
b. Check for 30 volts between terminal s #3 and #5 of the booster board and ter-
minal s #3 and
ii9
of the output board.
c. Check cue speaker.
5. No indi cation can be seen on VU meter when talking into the control room or studio
microphones, but the medium level channels operate O.K.
a. Interchange preamplifiers if on Iy one channel shows no indication.
b. Check for 30 volts between terminal s #7 and
118.
c. Check contacts on switch S 1.
6. No indication can be seen on the VU meter when feeding one of medium level
inputs.
a. Check the input switch, the channel mixer, and program/audition lever key.
4-1
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