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From: gnome@oliveb.UUCP (Gary)
Newsgroups: comp.sys.mac
Subject: Re: Ticking Mac
Message-ID: <5182@oliveb.UUCP>
Date: Tue, 15-Sep-87 17:49:37 EDT
Article-I.D.: oliveb.5182
Posted: Tue Sep 15 17:49:37 1987
Date-Received: Fri, 18-Sep-87 01:20:35 EDT
References: <740@tekirl.TEK.COM>
Organization: Olivetti ATC; Cupertino, Ca
Lines: 26

> 
> 
> My personal Mac at home has developed a rhythmic ticking, roughly a 1 second
> cycle.  I opened the case yesterday and used a plastic stethoscope to home
> in on the sound.  It was coming from the transformer on the power supply
> board (the one mounted fairly low, and probably the main supply transformer.)
> Up close, I could discern the ticking to be more complex than I thought.
> Don Chitwood


From what I can tell, it is a problem with the power supply not handling
intermittent load very well.  The ticking will stop when the CPU is doing
something very compute intensive.  Basically, it's causing the power supply
to respond to a series of non-repetitive pseudo-random increases in load
while executing a normal program -- which is easier than trying to filter
widely-spaced intense current pulses from the system (ie: the Ticking).
I am thinking about tracking-down the major offending areas on the mother
board and add some extra filtering (where there's room).

It's not going to cause your transformer to die, but, as always, I
strongly recommend putting a Kensington fan on your machine.  It'll
drop the inside temperature very well and is negligibly loud in
comparison to most HDU's...

Gary
(hplabs,allegra,sun,amdahl)oliveb!oliven!gnome