That also looks wrong but the resolution isn't great. Set the time base so that there are only about 3 cycles on the display (3 top horizontal lines) and post a photo. Also post the timebase and vertical amplifier settings that you use when take the new photo.
What's the DC voltage across the B+ and ground terminals?
With no power applied, what is the resistance between pins 13 and 14 of the 494?
What's the DC voltage across the B+ and ground terminals?
With no power applied, what is the resistance between pins 13 and 14 of the 494?
If it read 0 ohms from pin 13 to pin 14 and you were using channel 1 on the scope (so there's no chance it's being displayed inverted, the IC 'may' be defective.
Before you replace the IC, either pull the two C3228 drivers or pull all of the power supply FETs and post the voltage on each of the pins of the 494.
If you're not 'extremely' good at removing this type of driver board without doing 'any' damage to the board or vias, you should use chip-quik to remove it. It will take less than 2 minutes and there will be essentially no way to damage the board. If you damage even a single via and it becomes intermittent, it may be VERY difficult to repair the amp.
Before you replace the IC, either pull the two C3228 drivers or pull all of the power supply FETs and post the voltage on each of the pins of the 494.
If you're not 'extremely' good at removing this type of driver board without doing 'any' damage to the board or vias, you should use chip-quik to remove it. It will take less than 2 minutes and there will be essentially no way to damage the board. If you damage even a single via and it becomes intermittent, it may be VERY difficult to repair the amp.
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