If the TL072 is swinging above and below the voltage (0v) on the inverting input (pin 3) of the LM211 and the output of the LM211 isn't swinging to each of the power supply voltages on its power terminals, it is almost certainly defective.
Are you saying that there is no high-frequency (~100kHz) rail-rail oscillation?
Do you see the drive-frequency waveform at:
The input of the driver board?
The output of the driver board TL072?
The output of the LM211?
The gates of the output FETs?
Do you see the drive-frequency waveform at:
The input of the driver board?
The output of the driver board TL072?
The output of the LM211?
The gates of the output FETs?
It's strange that you get signal all of the way through without high-frequency oscillation. This could be from a few different things. The first I'd check is the feedback capacitor on the TL072 (typically pin 1 to pin 2). Or possibly the TL072. I've heard of TL072s from one batch/manufacturer working, while another would not.
You could also try injecting a high-frequency (80-100kHz) signal into the TL072 to see if that makes it through to the outputs cleanly.
You could also try injecting a high-frequency (80-100kHz) signal into the TL072 to see if that makes it through to the outputs cleanly.
To clarify... Without the FETs, you get drive to the gate pads of the output FETs but with the FETs, you get no drive to the gates of the FETs?
If that's correct, does the DC voltage on pin 2 of the 21844 (referenced to the negative rail) change with or without the FETs?
If that's correct, does the DC voltage on pin 2 of the 21844 (referenced to the negative rail) change with or without the FETs?
Without the fets in pin 2 is at 4.6v on the working card and 1.6v on the card that stopped functioning.
I'm leary about putting fets in. I did that earlier causing me to only have 1 working card now. It doesn't appear to be the 21844s chips tho.
I'm leary about putting fets in. I did that earlier causing me to only have 1 working card now. It doesn't appear to be the 21844s chips tho.
Do both 21844s have low voltage (on pin 2) on the dead board?
Negative rail as the reference, what's the DC voltage on pin 7 of U6 on the driver board?
Negative rail as the reference, what's the DC voltage on pin 7 of U6 on the driver board?
You won't get modulation at the drive frequency with a self-oscillating amp until it's fully functioning.
Modulation a the varying pulse-width. You've seen it with regulated power supplies.
The SD voltage on the 21844s is controlled by only 2 things, as far as I know. The MAX transistors pull it down during muting/protection and when they're defective. If you lift the MAX transistors, you can eliminate them (or the circuit driving them) as part of the problem. They are driven internally by a very low-current CCS to pull them up (when nothing is pulling that pin down). Lift the MAX transistors, one at a time, to see if the voltage on pin 2 of the 21844 goes towards 5v.
Modulation a the varying pulse-width. You've seen it with regulated power supplies.
The SD voltage on the 21844s is controlled by only 2 things, as far as I know. The MAX transistors pull it down during muting/protection and when they're defective. If you lift the MAX transistors, you can eliminate them (or the circuit driving them) as part of the problem. They are driven internally by a very low-current CCS to pull them up (when nothing is pulling that pin down). Lift the MAX transistors, one at a time, to see if the voltage on pin 2 of the 21844 goes towards 5v.
Both cards tl072 chips were defective.
Without fets everything looks fine again but now when I put the fets in it attempts to start but there is what appears the be ringing on the high side. The pictures are a progression of the high side wave
Im just glad I'm not blowing chips anymore with the fets in
Without fets everything looks fine again but now when I put the fets in it attempts to start but there is what appears the be ringing on the high side. The pictures are a progression of the high side wave
Im just glad I'm not blowing chips anymore with the fets in
