Re: Chirping //e

["Don Kelly" <don.kelly@sympatico.ca>]

The Apple II (all models) used a switching power supply. These power
supplies use high speed (frequency) switching to generate the required
output voltages (very simplistic explanation) which allows for smaller
components, more stable voltages and a bunch of other advantages including
cheaper construction.

Anyway it is not uncommon to hear these power supplies sing (especially
older ones) when transformers are not screwed down tight or the transformer
cores are loose. Equally it is not uncommon to hear them chirp when turned
on and/or off as the switching frequency builds up or falls off for similar
reasons. This does not normally impact their operation, its just annoying.

Switching supplies often employed varesistor which, in older versions when
they were "new" technology, had a tendency to partially come apart.
Basically they were a special carbon disk (small one) between two metal
contacts  ( ---|---) and the contacts came unglued from the disk.
Particularly during startup these components would chirp (loose again)
though normally they worked fine. Occasionally they went up in smoke when
the "looseness" of the connections generated excessive heat.

If it was up to me I would run the chirpy power supply until it failed, if
ever.


"Simon Williams" <ludditetech@mac.com> wrote in message
9f61cf69.0206250424.10b92aae@posting.google.com">news:9f61cf69.0206250424.10b92aae@posting.google.com...
> I have a //e Platinum which makes an gives out a high 'chirp' when I
> shut it down. I disconnected the speaker and disk drives and still it
> cheeps at me... sounds like it may be coming from the power supply,
> but it's one of those sounds that's really hard to pinpoint.
> Thought? Theories?
>
> Assuming the P/S is on it's way out, can I swap in one from a beige
> //e?
>
> SW