Replaced C13 with 1000pf cap. Now frequency is 228khz. Noise is not reduced and still visible at scope: it isn't a sine, but a little spike (like overshoot and oscillation). C13 is the only component that fix rail to rail oscillation frequency? Can be only the incorrect value of the C13 that give this wrong frequency?
Note: C13 is the cap from pin 1 to 2 of TL072 on my board version
Note: C13 is the cap from pin 1 to 2 of TL072 on my board version
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I don't think any of the logic ICs have anything to do with any of the audio or frequency of oscillation.
The TL072 'may' be able to influence the frequency of oscillation if it's defective.
Have you tried injecting a signal into the op-amp that drives the driver board to see if the amp would produce clean audio?
The TL072 'may' be able to influence the frequency of oscillation if it's defective.
Have you tried injecting a signal into the op-amp that drives the driver board to see if the amp would produce clean audio?
I lost track of the thread. I forgot noise was the issue.
I think the confusion about the input and signal ground may have been due to counting the pins in reverse.
The amp cannot produce output (so no noise) without the oscillation. Are you saying that when oscillation is completely absent, the amp is producing noise?
I think the confusion about the input and signal ground may have been due to counting the pins in reverse.
The amp cannot produce output (so no noise) without the oscillation. Are you saying that when oscillation is completely absent, the amp is producing noise?
I don't think the 4229 is compatible but I can't say for certain that it's not compatible. I'd suggest the FDA24N40F.
If you're ordering from a source that doesn't pack the IRS21844S ICs with desiccant and a humidity card, buy from a different source. Also be careful not to apply too much heat or apply the heat for too long. These ICs are very sensitive.
The following image shows recently unpacked IC (different IC but same type of packing). They were opened about 2 months after being shipped and the humidity card is still blue. The card will start to turn from blue to pink as soon as the package is opened so this package was obviously sealed.
If you're ordering from a source that doesn't pack the IRS21844S ICs with desiccant and a humidity card, buy from a different source. Also be careful not to apply too much heat or apply the heat for too long. These ICs are very sensitive.
The following image shows recently unpacked IC (different IC but same type of packing). They were opened about 2 months after being shipped and the humidity card is still blue. The card will start to turn from blue to pink as soon as the package is opened so this package was obviously sealed.
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