Re: gEDA-user: buzzing board

[DJ Delorie <dj@xxxxxxxxxxx>]

I got the new parts today.

Redux:

Adding 100uF electrolytic, swapping in 10u 25v 1206 ceramic did NOT
get rid of the buzzing, just reduced it a little.

Swapping in 10u 16v 1206 tantalum with the 100u DID get rid of the
buzzing, both the low pitch and high.

There's still 80mV P-P spikes on the line[*] at 8.3KHz (line refresh
rate) but that's 6X better than the 500mV ripple it used to have.

Lesson: for heavy-noisy loads at audible frequencies, you need
sufficient non-ceramic decoupling before (or instead of) the ceramics.


[*] http://www.delorie.com/electronics/alarmclock/


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