Tait T830 Series, Руководство по обслуживанию

Страница: 154 / 284

31/01/96 Copyright TEL
5.5.2 Synthesiser
VCO out of lock.
Check 5V reg. &
supply resistor
to each IC.
20V inverter
supply faulty.
9V present on
Q1 divider buffer?
Check 9V supply.
DC V present
on Q1?
Check TCXO
& reference
divider path.
VCO freq. correct? Go to C.
Synthesiser OK.
No VCO RF output.
Check biasing
resistors & Q1.
N
N
N
N
N N
N
N
N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
N
Y
Y
VCO trimmer
freq. range OK?
VCO OK.
Check signal
path from VCO
to prescaler.
Check VCO tuning
caps & trimmer.
20V present
on IC6 pin 8?
Correct ref.
on IC5 pin 8?
Prescaler output
freq. present on
IC5 pin 4?
Does IC5 pin 1
PDA change level
at the programmed
synth. freq?
Check synth. data
loading ccts;
change EPROM;
change synth. IC5.
Does control line
O/P level change
on IC6 pin 1?
Check loop filter
cct around IC6.
9V reg. present at
VCO amp. Q4/Q5?
Check Tx reg.,
Q211 & 9V reg.
N
Y
DC V present
at Q4 & Q5?
Check biasing
resistors, Q4 & Q5.
N
Y
8.3V present
at VCO?
Check Q5 C
multiplier (synth).
N
Y
DC V present at
VCO, Q1, Q2 & Q3?
Check biasing
resistors, Q1,
Q2 & Q3.
N
Y
Synthesiser OK.
Check continuity
between VCO &
IC6 pin 1 O/P.
N
N
N Y
A (Refer to VCO circuit diagram)
Replace VCO.
Replace
if faulty.
Capacitors OK? Check
for cracks, shorts, etc.
Y
N
+5V present at
TCXO, IC7, IC4,
IC3, IC5 & EPROM?
Does VCO trimmer
adjust for stable
control line
between 5 & 15V?
Does VCO trimmer
adjust for required
frequency range
between 5 & 15V?
Is 8MHz VCO range
achieved between
5 & 15V?
Does IC3 pin 3 O/P
freq. change with
VCO trimmer when
VCO not locked?
N
N
Check *C5, *C3, *C4,
VC1, D1-D4 in VCO.
B (Refer to synth. circuit diagram)
Check at IC3
pin 3; replace
IC3 if no output.
Continued on next page.