T830 Series II Base Station Equipment 136-174MHz Service Manual

C5.12 T836/837 Fault Finding M830-00
5.7.3 Synthesiser
Refer to the synthesiser circuit diagram (sheet 7) in Section 6 and the VCO circuit diagram
in Part E.
A
B
No VCO RF output.
VCO out of lock.
9V present at
VCO Q4/Q5?
Y
N
Check Tx reg.,
Q610 & 9V reg.
+5V present at
IC700, IC710,
IC740, IC720
& IC730?
N
Check 5V reg. &
supply resistor
to each IC.
DC V present
at Q4 & Q5?
Y
N
Check biasing
resistors, Q4 & Q5.
Y
20V present
on IC750 pin 8?
N
20V inverter
supply faulty.
8.3V present
at VCO?
Y
N
Check Q5 C
multiplier
(synth).
Y
9V present on
Q795 divider buffer?
N
Check 9V supply.
DC V present at
VCO, Q1, Q2 & Q3?
Y
N
Check biasing
resistors, Q1,
Q2 & Q3.
Y
DC V present
on Q795 emitter?
N
Check biasing
resistors & Q795.
Capacitors OK?
Check for cracks,
shorts, etc.
Y
N
Replace
if faulty.
N
Y
Does VCO trimmer
adjust for stable
control line
between 5 & 13V?
Replace VCO.
Y
VCO freq. correct?
Y
N
Recheck
programming
via PGM800Win.
Check VCO tuning
caps & trimmer.
N
VCO trimmer
freq. range OK?
Y
N
Does VCO trimmer
adjust for required
frequency range
between 5 & 13V?
Y
Check #C5, #C3, #C4,
CV1 & D1-D4 in VCO.
N
Is 8MHz VCO range
achieved between
5 & 13V?
Synthesiser OK.
Y
VCO OK.
Continued on the next page
23/07/99 Copyright TEL