John, at the present time, the amp oscillates as soon as i start it. I simply power up the amp with the input shorted to ground, with or without load, and it immediately oscillates. I have replaced the IC on one of the boards and kept the input cap at 2.2uF, and it works.
To me it seems that the IC is damaged, and the other blown IC behaves identically. The second blown IC also worked until i changed the input capacitor with a larger one.
To me it seems that the IC is damaged, and the other blown IC behaves identically. The second blown IC also worked until i changed the input capacitor with a larger one.
Okay, I see your talking about the damaged IC oscillating. If switching ICs (and nothing else) changes the behaviour, then, yes, the oscillating IC is bad. Even with a large C on the input, C27 in the feedback loop becomes the low frequency limiter. Any DC on the output would be for a short period, but could possibly blow the chip.
With a multi meter, check for DC across the source when you first turn it on. Check for high voltage from source to input due to AC line leakage (if applicable) that can kill the IC input stage even if the amp is off when connecting this source to the amp's input. Check the load impedance and speaker wires for shorts just to be sure.
What exactly is your signal source? It seem to blow stuff up.
With a multi meter, check for DC across the source when you first turn it on. Check for high voltage from source to input due to AC line leakage (if applicable) that can kill the IC input stage even if the amp is off when connecting this source to the amp's input. Check the load impedance and speaker wires for shorts just to be sure.
What exactly is your signal source? It seem to blow stuff up.
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I have checked everything you have said, and the source does seem to be ok, at turn on it has almost zero DC, and some DC is present at running time, 1,6mV as I have measured before. Also, no high-voltage leaks anywhere.
I have however ordered other IC's and built a more serious PS, and everything seems to be OK, even with larger capacitance at the input. It also sounds a lot better.
I'm giving up on this matter as one of those questions which may never be answered. You might have been right when you mentioned the faked IC's, the new ones have absolutely no problem event on the old PCB.
Thank you for all your replies.
I have however ordered other IC's and built a more serious PS, and everything seems to be OK, even with larger capacitance at the input. It also sounds a lot better.
I'm giving up on this matter as one of those questions which may never be answered. You might have been right when you mentioned the faked IC's, the new ones have absolutely no problem event on the old PCB.
Thank you for all your replies.
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