EM84 magic eye does not close on FM on Philips B4X92A (Techniek Radio/TV)

door tdperez , Eindhoven, 20.10.2022, 18:22 (557 dagen geleden) @ Maurice

Hi Maurice,

Thank you for your answer.

Testing with the radio off, when the FM button is pressed (which activates both SK4 and SK5), there is a DC path between Em84-pin1, R11, and R18/R21. Are you suggesting that there is a coupling capacitor somewhere that should be blocking DC between R11 and R18/R21, but may be shorted/leaky?

I imagine that SK4 should either connect terminals SK4-7 to SK-6 or SK4-6 to SK4-5, but never the three of them. Is this what makes you say that there should not be a DC-path between R11 and R18-22?

Do you know how should I read the SK diagrams? The bold vertical lines, do they indicate connections when the switch is ON or OFF? When the switch changes state, would the bold vertical lines move up (for example, changing the connection from 5-6 to 6-7 on SK4)? Being able to read these switch diagrams would help understanding the intended DC path.

I hope these questions aren't too silly. Thanks again!

(once again link to the original diagram for ease of reading)