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Low voltage on startup resistor

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sarry86:
Greetings, I have a low voltage on a startup resistor on my Sony DAV-DZ350, the resistor is 100k ohms and checking it on multimeter, it shows exactly 100k ohms, it generate only 2.44vdc which isn't enough to start up the power IC, any tip on how to fix this? I have replaced the control IC twice to no avail

inse:
Disconnect R936 and see if it tries to generate output pulses.
The voltage before the 100k is OK?

RoGeorge:
Check the electrolytic capacitors, particularly in appliances with switched-mode power supply (SMPS).  The electrolytic capacitors dry out with time and develop a high ESR (Equivalent Series Resistance).  This leads to all kind of strange behavior (more often manifesting when when the appliance is cold).

Replace any electrolytic with a bulged top.  Sometimes the electrolytics might fail without any mechanical hints.  Measure their ESR with a good ESR-meter that can measure in circuit, without needing to desolder the capacitor first.

sarry86:
I tried, there's 1.85v with or without R936 connected, if I desolder a startup resistor leg to startup pin, the resistor gives exactly 230~ volts! Does that mean it is open? 😳

nali:
Does the "~" refer to AC volts? That's wrong, you should be seeing a DC voltage, so it looks like C901 has probably failed (plus any other electrolytic which may be in parellel with it outside the cropped schematic)

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