Panasonic KX-F900 Service Manual page 75

(3) The broken parts repairing details
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(D101)
Check short-circuit of terminal 4. It D101 is short-circuited, F101 will be melted (open). So in this case,
replace the 60th parts (D101, F101).
(Q101)
The worst case of Q101 is a short-circuit between the Drain and Gate because damage expands to IC101.
This is due to of very high voltage through the Gate circuit which is composed of D104, R107, R114 and
R121. Then you should change all of the parts listed as follows:
F101, Q101, D104, R107, Rl14, R121, IC101.
(IC101)
Occasionally, it exists as the sole case of a broken IC101. You should exchange.
(D201)
If D201 is broken, the oscillation circuit of the power supply cannot operate. Check it with an electric tester.
(D202)
Occasionally, this part short-circuits. In this case, you can listen to the click sound of intermittent oscillation*.
Check the resistance between 24V and GND.
*Intermittent Oscillation:
This happens when the power supply balance is broken and loads as a perfect open or short-circuit of
output. The graph of Intermittent Oscillation is shown as follow.
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