With PS fets out of circuit - should I see a nice square wave drive at the fet pads. Or a not so nice looking drive due to the regulation?
When the FETs are out of the circuit, regulated power supplies have a square wave.
This amp uses an H-bridge drive. Half of the PS FETs will have a square wave.
The other half will have a floating drive. Confirm that there is no DC on the source leg of the FETs without drive, then (if there is no DC) check for drive by connecting the scope ground to the source of the FETs.
This amp uses an H-bridge drive. Half of the PS FETs will have a square wave.
The other half will have a floating drive. Confirm that there is no DC on the source leg of the FETs without drive, then (if there is no DC) check for drive by connecting the scope ground to the source of the FETs.
The first one is what's I'd expect but the second seems to be shifted up.
Are you sure that you had a good scope ground to the source pad?
What do the other 2 banks look like (there are two floating banks and two grounded banks)?
Are you sure that you had a good scope ground to the source pad?
What do the other 2 banks look like (there are two floating banks and two grounded banks)?
The first picture is one bank.
The second picture is the other bank - if I hold the probe in place it will slowly sink to match the waveform on the first bank. This pic was when I first place the probe.
Yes good ground on the source pad (soldered).
The second picture is the other bank - if I hold the probe in place it will slowly sink to match the waveform on the first bank. This pic was when I first place the probe.
Yes good ground on the source pad (soldered).
I think they're OK. I've never used a loading capacitor on this amp but it may be more definitive if you're questioning the drive due to some problem you're having.