The Magic Smoke escaped :(
The Magic Smoke escaped 
I played with the negative feedback today. I started at the minimum of 500 ohms, where ~500mW gets close to 50 watts out. Then I turned the drive down on the radio to show 10 watts output. I reduced the negative feedback by increasing the resistance. I turned it up just a little bit and the power output came up significantly. Somewhere around 50 watts with the same drive level. I turned it up a little bit more, I think the power got near 100 watts, but I don't recall exactly. Then it started to smoke. The Resistor R21 in the High Voltage Mosfet Switch section (330 ohms to ground) started smoking. At the same time, the status LEDs went out and the LCD went out. The fuses didn't blow. The mosfets don't appear to be shorted either.
My guess is maybe the MPSA42 transistor shorted and took out that resistor, and the voltage regulators went into short protection mode and cut off all of the power. I'll have to do some more investigating of the components around there to see what needs to be replaced...
I played with the negative feedback today. I started at the minimum of 500 ohms, where ~500mW gets close to 50 watts out. Then I turned the drive down on the radio to show 10 watts output. I reduced the negative feedback by increasing the resistance. I turned it up just a little bit and the power output came up significantly. Somewhere around 50 watts with the same drive level. I turned it up a little bit more, I think the power got near 100 watts, but I don't recall exactly. Then it started to smoke. The Resistor R21 in the High Voltage Mosfet Switch section (330 ohms to ground) started smoking. At the same time, the status LEDs went out and the LCD went out. The fuses didn't blow. The mosfets don't appear to be shorted either.
My guess is maybe the MPSA42 transistor shorted and took out that resistor, and the voltage regulators went into short protection mode and cut off all of the power. I'll have to do some more investigating of the components around there to see what needs to be replaced...
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