Tait T830 Series, Service Manual

Page: 159 / 284

Copyright TEL 31/01/96
5.5.6 Audio Processor
Does exciter
modulate?
Check alignment
of modulators.
Demodulated audio
frequency response
flat between
50Hz & 300Hz?
Check audio
path between
integrator &
phase modulator.
Check loop filter
(IC6a) & associated
components.
Audio output at
IC104 pin 7?
Check audio
path to VCO
control line.
Check
buffer IC104b.
Does exciter
modulate?
IC101 pin 6
at 9V?
Audio signal at
IC101 pin 4?
Check IC101 or audio
path between line trans-
former & multiplexer.
Connect audio
to line input;
key exciter.
Select standard
audio configuration.
Check Q102 is not faulty or
being turned on inadvertently.
Demodulated
audio frequency
response as
per Section 4.6?
Audio processor
OK.
Key exciter &
lock synthesiser.
Connect 1kHz audio
to CTCSS input.
N
Y
Y
Y
Y
N
N
N
Y
N
Y
Y
Y
Y
N
N
N
N
N Y
N
Y
Y
N
N
N
N
N
Y
Y
Y
Y
Audio superimposed
on 200kHz signal
IC7 pins 9 & 13 (synth)?
200kHz clipped
triangle wave at
IC7 pins 8 & 12?
Check IC7e, IC7a, C44,
C48, Q8, Q9, Q10 & Q11.
Audio output at
IC103c pin 8?
Audio output at
IC103b pin 7?
Check IC103b.
Check low pass
filter IC103c.
Audio frequency
response IC103c
pin 8 flat 300Hz
to 3kHz?
Check low
pass filter
IC103c.
Audio frequency
response IC103d
pin 14 6dB/octave
slope?
Check integrator
IC103d.
Audio signal at
IC103a pin 1?
Audio signal at
IC102d pin 14?
Audio signal at
IC102c pin 8?
Check audio path between
limiter IC103a & summing
amp. IC103b.
Check IC103a.
Check IC102d or audio
path between pre-emphasis
network & limiter.
Check IC102c or audio
path between multiplexer
& pre-emphasis network.
Check pre-emphasis
network IC102c
&/or low pass
filter IC103c.