Sony PCS-1500 Service Manual page 149

m) Check the muting function by observing the output waveform at TP143. [MUTE CONTROL]
→ When the muting function works normally, no output is produced because the mute function
works when operation of the infrared transmitter is stopped or incoming infrared light is
completely intercepted before reaching the receptor.
→ When any output signal is produced under the above described condition or when the video
signal is not output even though the infrared transmitter modulates and transmits the video
signal, the circuit is suspected to be abnormal.
Locate the poor soldering of the components having reference number 160 series. Or replace
D161, Q161 to Q164 one after another and find out the location of error by confirming the
waveform.
* The composite horizontal and vertical sync signal is separated from the video signal at the
circuit before the D161 anode. The sync signal is rectified at the D161 cathode, then video
signal detection is performed at Q163 and Q902. When the video signal is not detected,
mute control is driven at the input circuit of the final video amplifier stage. Therefore, mute
control can be judged if it works correctly or not by checking the Q164 base potential.
4. When RX-47 is suspected to be defective
a) If any signal cannot be check at IC451 pin-1 while receiving the incoming SIRCS signal.
→ Replace IC451.
b) If SIRCS signal cannot be checked at TP451 even the above step a is confirmed.
→ Replace IC452.
c) If SIRCS signal cannot be checked at MA-97 side.
→ Poor soldering of CN404. Replace CN404 or others as needed.
PCS-1500/1500P
4-1. Check Items Before Starting Self-diagnostics
4-19