Tait T850 II Series User Manual

C5.18 T856/857 Fault Finding M850-00
31/09/98 Copyright TEL
5.7.7 Audio Processor
N
IC240 pin 6
at 9V?
Key exciter &
lock synthesiser.
Connect 1kHz audio
to external CTCSS input.
Does exciter
modulate?
Audio output at
IC260 pin 8?
NY
Check audio path to
VCO control line.
Check alignment
of modulators.
YN
Audio output at
IC260 pin 1?
Y
Check buffer IC260
pins 8, 9 & 10.
N
Audio output at
IC260 pin 7?
Check low pass
filter stage IC260
pins 1, 2 & 3.
Y
Check stage IC260
pins 5, 6 & 7.
N
Demodulated audio
frequency response
flat between 50 & 300Hz?
Y
Check low
pass filter
stage IC260
pins 1, 2 & 3.
N
N
Y
Audio frequency
response IC260
pin 1 flat 300Hz
to 2kHz?
Audio frequency
response IC210
pin 8 6dB/octave
slope?
Check integrator
IC210 pins 8, 9, & 10.
N
Y
Audio superimposed
on 200kHz signal
IC720 pins 9 & 3 (synth)?
Check audio path
between integrator
& phase modulator.
N
Y
200kHz clipped
triangle wave at
IC720 pins 8 & 4?
Check IC720, Q710, Q720,
Q730, Q740, D710, D720,
C727, C729, C724 & C725
N
Y
Check loop filter
(IC750, pins 5, 6 & 7)
& associated
components.
Select standard
audio configuration.
Check pre-emphasis
network IC230 pins 12,
13 & 14 &/or low pass
filter IC260 pins 1, 2 & 3.
N
Y
Connect audio
to line input;
key exciter.
Does exciter
modulate?
YN
Demodulated
audio frequency
response as per
Section 4.5?
Audio processor
OK.
Audio signal at
IC210 pin 14?
Y
N
Audio signal at
IC230 pin 1?
N
Audio signal at
IC230 pin 14?
Y
N
Audio signal at
IC240 pin 4?
Y
N
Y
Check Q260 is not faulty or
being turned on inadvertently.
Y
Check audio path between
limiter IC210 pin 14 &
summing amp. IC260 pin 7.
Check IC210
pins 12, 13 & 14.
Check IC230 pins 1, 2 & 3 or
audio path between pre-
emphasis network & limiter.
Check IC230 pins 12, 13 & 14
or audio path between multiplexer
& pre-emphasis network.
Check IC240 or audio
path between line trans-
former & multiplexer.

Tait T850 II Series Specifications

General

Brand	Tait
Model	T850 II Series
Category	Accessories
Language	English