High Voltage from LG Microwave Inverter

[GLaDOS]

Hello everyone. I salvaged an LG inverter board and wanted to try powering it. Doing some research, I learned Panasonic inverters require a 220Hz square wave on the control pin, so I applied a square wave with 10% duty cycle and then slowly increased duty cycle without success. It seems like LG inverters use a different frequency or another control method? Could someone more knowledgeable provide some insight?

I have also attached annotated images of the PCB, focusing on the input section. There are 2 optocouplers, I assume one provides a feedback to the microwave control board and the other is what controls the power output of the magnetron. You can see how I connected an Arduino generating a 220Hz square wave at variable duty cycle to the anode of the input optocoupler, other end goes through a resistor to ground. Additionally, I tried 1kHz, 5kHz, 10kHz, but with no success. There's probably a specific frequency I need to use. Unfortunately, I am missing the front panel to the logic board, so I am unable to use my scope to figure out the exact control signal used. There's probably a bunch of safety measures, so the board likely won't even send the signal in the first place.

I'm doing all these tests hooked up to a variac providing 120V AC to input. I also noticed sense resistors connected to the output of the bridge rectifier, they go through resistor dividers to the microcontroller, likely used to detect when power is applied. Whats interesting is all the ICs except for the 2L05...(can't read the rest of the letters) are connected to either the 5V regulator or VCC(12V in my tests). The gate driver goes through a P channel MOSFET, which is driven by a BJT going to ground. Microcontroller should pull the base high, pulling the gate to 0V, turning on the MOSFET. This never happens in my tests.

I don't really know what else to do, other then spend an eternity trying different frequencies and duty cycles, which may not even work. I would really appreciate some guidance on how to proceed. Thanks!

[Twospoons]

  There's no reason to assume the LG control signals resemble the Panasonic ones, in fact you could pretty much guarantee they will be different.
Without a schematic you are flying blind.  Google search on the PCB number turned up nothing.  So unless you want to reverse engineer the thing yourself, you may be better off just using it for parts.