Two points to make here:
1. You show DC voltages across the transformer primary and secondary, you can't measure these voltages with a normal test meter and they are not DC anyway.
2. There will be very high voltages on the primary side, easily enough to kill you. Be extremely careful connecting anything to them, including testmeter probes and under no circumstances try to measure voltages from one side of the transformer to the other. There is a lines, roughly side to side through the 'varistor' (more likely a high voltage capacitor), through the transformer and then through the 4 and 8 pin optocouplers (PC1, PC2?) that divides the primary high voltage side from the safer secondary and isolated low voltage side.
The first test to do is connect the AC power and measure the DC voltage across the 150uF/400V capacitor. It should have around 210V DC across it, if that is missing, either the input fuse is blown or the bridge rectifier has failed. If they are OK and the voltage is much lower, most likely the capacitor itself has failed.
Brian.
The big capacitor is fed directly from the bridge rectifier which in turn is fed through the filter and fuse from the AC input. It could be the NTC if that's what is hidden under the white silicone but to get 24VDC implies there is a high impedance path very close to the AC input connection.
Imcool1, with the AC unplugged and the board left to discharge for a minute or so, use your testmeter on the resistance range to measure across the pins of FS1, then the green disc near the AC connections and tell us what you get.
You could also measure from each of the middle two pins of BD1 to each of the AC input wires and tell us the resistance there too.
*UNDER NO CIRCUMSTANCES DO THIS WITH THE POWER TURNED ON*
Brian.
The big capacitor is fed directly from the bridge rectifier which in turn is fed through the filter and fuse from the AC input. It could be the NTC if that's what is hidden under the white silicone but to get 24VDC implies there is a high impedance path very close to the AC input connection.
Imcool1, with the AC unplugged and the board left to discharge for a minute or so, use your testmeter on the resistance range to measure across the pins of FS1, then the green disc near the AC connections and tell us what you get.
You could also measure from each of the middle two pins of BD1 to each of the AC input wires and tell us the resistance there too.
*UNDER NO CIRCUMSTANCES DO THIS WITH THE POWER TURNED ON*
Brian.
I managed to trace some of the circuit but it is quite difficult with some parts obscured by others in the photos.
It looks like the optocoupler drives the triac and the AC side of it is kept in partial conduction by a phase shift circuit comprising R7, R6, R5, R4 and what I would guess is a capacitor, probably the brown one just visible to the top left of the 150uF one. I'm guessing, because I can't see any values, that it is responsible for the 24V you see and that in turn is just enough to start the switcher oscillator and produce a low voltage output.
The '1002' MOSFET looks more like a double diode to me so I wouldn't expect a normal meter to see any DC across it. The 'Varistors' are also high voltage capacitors I think.
I'm still puzzled about the power source to the optocoupler LED, intuition says it gets power from somewhere else but I assume this is the only power supply in the device.
Brian.
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