Re: Reversed polarity cap killed PSU board
I've heard people blaming caps with too low ESR for supply whine, but in my experience it was always a case of loose windings in a transformer or coil and a bit of lacquer always the fix. Also if it didn't work when you got it, you have no way of knowing if the noise wasn't there in the first place.
I recap PSU's before failing. If I leave the 5V cap before the choke as it was and recap rest everything is ok.
Replace that cap with some ULESR and it whines. Replace with some poorer cap, whine is gone.
And no, it doesn't respond much to load.
Tweaking them for lowpass IS tuning.
But PI filters ain't even lowpass. They are DC pass-trough.
It will usually be more, not less.
That depends on the suitability of the cap. High ESR can mean higher losses in cap, not necessarily better filtering.
Also. Unloaded stuff isn't worth anything.
Same with temperature.
And same with feedback.
Low ESL cap can act differently as well.
Even PWM regulation is different then.
Oklahomawolf [from jonnyguru] embarrassed himself publicly by making that mistake.
Recapped unit had worse ripple than it did with bad caps.
Can you link me to that thread ?
I've heard people blaming caps with too low ESR for supply whine, but in my experience it was always a case of loose windings in a transformer or coil and a bit of lacquer always the fix. Also if it didn't work when you got it, you have no way of knowing if the noise wasn't there in the first place.
I recap PSU's before failing. If I leave the 5V cap before the choke as it was and recap rest everything is ok.
Replace that cap with some ULESR and it whines. Replace with some poorer cap, whine is gone.
And no, it doesn't respond much to load.
Tweaking them for lowpass IS tuning.
But PI filters ain't even lowpass. They are DC pass-trough.
It will usually be more, not less.
That depends on the suitability of the cap. High ESR can mean higher losses in cap, not necessarily better filtering.
Also. Unloaded stuff isn't worth anything.
Same with temperature.
And same with feedback.
Low ESL cap can act differently as well.
Even PWM regulation is different then.
Oklahomawolf [from jonnyguru] embarrassed himself publicly by making that mistake.
Recapped unit had worse ripple than it did with bad caps.
Can you link me to that thread ?
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