Start Up Fails When HDD Connected

Black Hole said:
You would never fit a non-electrolytic 4μ7 cap on the board!
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Actually you could using modern MCC capacitors. You can certainly get 4.7uF, but I'm not sure what voltage they go up to. But my memories of the photos of what needs changing I would expect to get one in there.

But personally I would use a teardrop tantalum one, unless the circuit designer is relying on some leakage through the capacitor.
 
Black Hole said:
25V or 50V.

They top out at 10μF, but I didn't realise they went that far up in such small packages.
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Yeah, the cellphone market (along with other miniature devices) has really pushed the sizing. You do have to be careful though, as the capacitance value derates the closer you get to maximum operating voltage. By the time max V is reached you can be at 1/3 to 1/4 rated C, especially for low voltage ones, like below 10V. Standard thing to do is use a capacitor that has a massively greater V rating than the circuit seems to require, or make allowances for the derating.

The other problem (just mention it to an audiophobe) is that they are microphonic, in standard ceramic/crystal microphone style, and/or because of the capacitance change with voltage you get 'modulation' effects when using them as coupling capacitors.
 
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