JRC JRL-2000F Service Manual page 26

.", When PA fails (2):
Phenomena:The input side of PA is grounded for high frequencies.
Gauses :(1 )One of FETs of CAH-377 has short-circuited.
(2)0ne of input transformers of CAH-377 has short-circuited or been
broken.
(3)0thers
< Troubleshooting procedures >
(1) Make PA generate power by itself if possible, and check for the heat gener
ated by the resistors of the combiner to find which PA unit is out of order.
(2) Check the external appearance of FETs of CAH-377 power amplifier for damage,
etc.
(3) As shown in Fig. 12, in the case of a short-circuit between gate (G) and source (S),
the resistance value between gate (G) and source (S) of each TR12 to TR16 is
about 54
n :
lf all FETs are normal, the resistance value betwee11 gate (G) and
source (S) of each FET is about 1
0
k
n .
(4) lf all FETs are normal, check for a short circuit or breakage in the transformers. To
compensate the external observation, turn the power on and compare the
wavefroms of each·part.
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