Tait T860 Series II, Service Manual

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M860-00-Preliminary
T869 Fault Finding D4.7
Copyright TEL 30/06/98
4.5 Fault Finding Charts
4.5.1 PA
Are RV69 & RV63
fully clockwise?
Rotate clockwise:
RV63 first, RV69 second.
RF circuitry OK.
Replace splitter hybrid.
Return PA to your local
Tait service centre.
Replace combiner hybrid.
N
N
N
Y
Y
Y
N
Y
N
N
N
Is maximum power >100W
over entire frequency range?*
Is maximum power >100W
over entire frequency range?*
Y
*Frequency Ranges
T869-10: 220-244MHz
T869-20: 243-270MHz
T869-30: 265-285MHz
Y
Y
N
Y
Is the drive from the
exciter 400-600mW?
Set drive to
400-600mW.
Is #IC6 output >20W?
(see Figure 4.1)
Check the condition of
splitter hybrid L500.
Are there any shorts
between the splitter wires
or broken wires?
Q59/Q60, Q61/Q62
outputs each >60W?
(test in pairs
as per Figure 4.1)
Check the condition of
combiner hybrid L501.
Are there any shorts
between the combiner wires
or broken wires?
Is R405 hot to touch
when PA keyed?
Y
Check #IC6 pin 4 >13V.
Check #IC6 pins 2 & 3 >12V.
Check C101, R133, R134,
R135, C102 & C116.
Replace module.
N
Set RV69 (driver power clamp)
to 110W (refer Section 3.3).
Check components in LPF.
Check output N-type connector
for short circuit or excessive wear.
Replace parts as necessary.
With no RF present,
check collectors >13V.
Check for shorts around
transistor base matching caps.
Check transistor junction
resistance (see Section 4.2).