Tait T855 - Page 193

M850-00 T856/857 Fault Finding C5.17
Copyright TEL 31/09/98
5.7.6 T857 Exciter Drive Amplifier
Check
power rails.
Check VCO.
Drive amp. OK.
N
N
Y
Y
N
Y
Y
N
Y
N
Y
9V at Q304 collector?
0.5V at Q304 base?
9V at Q305 collector?
Key exciter &
lock synthesiser.
Y
N
9V at Q303
collector?
Y
>4V present on
IC300 pin 1?
Check IC300.
Check Q302
& Q303.
>2V RF at
VCO output?
N
>1V RF at R323?
N
Y
Check attenuator pad
R517, R518, R519.
>0.5V RF at
Q304 base?
Check C314, #C315,
#C316, Q304, L305,
D201, D202, D203.
>5V RF at
#C321, #R330?
N
Check Q304.
>1V RF at
Q305 base?
Check si
g
nal path
between Q304 & Q305.
>5V RF at
Q305 collector?
Check Q305.