User's Manual

M889-00
Fault Finding 5.7
Copyright TEL 02/10/95
5.5 Fault Finding Charts
5.5.1 PA
Is maximum power
>90W @ 800-870MHz?
Are RV69 & RV63
fully clockwise?
Is the drive from
the exciter 4W?
Rotate clockwise:
RV63 first, RV69 second.
Set drive to 4W.
RF circuitry OK.
Replace splitter hybrid.
Check collectors >13V.
Check for shorts around
transistor caps.
Check transistor junction
resistance (see Section 5.2).
Is maximum power
>90W @ 800-870MHz?
Return PA to your local
Tait service centre.
Replace combiner hybrid.
Check components in LPF.
Check output N-type connector
for short or wear.
Replace parts as necessary.
N
N
N
Y
Y
Y
Y
N
N
Y
Y
N
Y
N
N
Y
Y
Is Q2 output >40W?
(see Figure 5.1, A & B)
N
Check the condition of
splitter hybrids L13, L14 & L15.
Are there any shorts
between the splitter wires
or broken wires?
Q3, Q4, Q5 & Q6
outputs each >30W?
(test each individually
as per Figure 5.1, C & D)
Check the condition of
combiner hybrids L40, L41 & L42.
Are there any shorts
between the combiner wires
or broken wires?
Are R17 & R17A hot to
touch when PA keyed?
Check Q1 collector >13V.
Check Q2 collector 5-14V.
Check for shorts around
transistor caps C2, 3, 9,
19, 10, 11, 12, 13 & 14.
Check transistor junction
resistance (see Section 5.2).