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OptoIsolators
Opto couplers are easy to identify as the straddle the power isolation barrier around the PSU area.
they usually have 4 or 6 legs.
There are two types
1) the standbye type these are usually turned on/off by the micropro chip
check for 5v on the legs of the IR reciever (it has 3 legs) as its usually fed with the same power as the MicroPro chip
2) the other type is for HT level control and they can be identified by looking for a small preset resistor nearby or by tracing the pcb tracks for the optoisol to see if they go near a preset resistor
TESTING OPTO'S
opto-coupler can be tested with TWO OHM METERS.(with power off/disconnected of course)
Connect one across the output (mains side of the isolation barrier) so that it gives a reading
and apply voltage(ON DIODE TEST or ohms)with the other at the input (tv side).
When connected one way round if the output reading changes the opto-coupler is probably OK.
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