Re: "Clicking" II+ power supply

["John B. Matthews" <nospam@nospam.com>]

In article <1147656612.398919.134200@j73g2000cwa.googlegroups.com>,
 "N.N. Thayer" <nnthayer@hotmail.com> wrote:

> I have an Apple II+ whose power supply is a little finicky. Sometimes,
> when I turn it on, it causes the speaker to emit a fast clicking noise,
> about two clicks per second, and the screen flashes in sync with the
> clicks.  If I turn it off, let it sit for a few moments, and then back
> on, everything works fine.  Other times, when I turn it on, it'll start
> up normally but I'll hear a moderately loud *pop* from right beneath
> the power switch.  This in particular scares me.

When a switching power supply is overloaded, its operating frequency 
falls through the audible spectrum until it shuts down. This cycle 
repeats, causing a "chirp" sound at a few Hertz.

The pop may be a capacitor discharging.

> I've never been inside one of these power supplies but it basically
> sounds to me like this one's ready to go at any time.  Should I be
> worried about any damage to my II+ that I cannot as yet see?  Could I
> perhaps extend the life of the power supply by not using the power
> switch directly, but instead employing one of those System Saver fans?

When I had one like this, I just left it on until I could locate a new 
power supply. I've heard of people drilling them open to repair them, 
but I assumed the rivets and warning sticker meant me:-)

-- 
John Matthews
jmatthews at wright dot edu
www dot wright dot edu/~john.matthews/