🚀 go-pugleaf

In article <468@unh.UUCP<, al671@unh.UUCP (Anthony   Lapadula) writes:
< I don't know how common this problem is, but my 1040 ST emits a high
< pitched whine whenever it's in operation.
< 
< I had this checked out about 1 month after I bought the system, and was
< told that the sound is probably a sub-frequency of the switching
< power supply.
< 
< Whatever it is, it's *very* annoying, and I wish to make it stop.....
< 
< Any hints or suggestions?  Note that I'm not a hardware hacker, so
< please include copious instructions (unless your suggestion is
< to bring the ST to a _real_ repair shop :-).
< 
< Many thanks.
< 
< /*
< **      What, you wanted something funny?
< **             --- Anthony Lapadula
< **             (That's ...!unh!al671 to you!)
< */

My 1040 ST has started doing the same thing recently.  Not all the time - 
sometimes it will start whining after an hour or so of operation, sometimes
it doesn't start at all.

I at first though it was the monitor, since the the whine often coincides
with black background on the screen (as when running PC-Ditto).  But
sometimes it starts up when the modem hangs up.  Weird.

I am now sure that it is not the monitor, even though it sounds like a
typical monitor whine.  The proof of this is that it stops when the monitor
is off.

Anthony is right, it is very annoying.  Blaming the power supply makes some
sense - a resistor and capacitor are probably forming some type of R/C 
resonant circuit.  Replacing the filter capacitor would probably help.

I know enough electronic theory to come up with the above explanation,
but not enough to know what to change.  Is there an EE out there who can
help?
-- 
Ron DeBlock	KA2IKT		213 River Dr.
...!rutgers!galaxy!argus	Lk Hiawatha, NJ 07034
ron@wilbur.njit.edu		(201) 316-6807
"Oooo...that's mean!"  "No, just average."