bowman@phoenix.Princeton.EDU (Hiroshi Bowman) (04/09/90)
Thanks to everyone who responded to my inquiry concerning the analog
failure problem on the Macintosh Plus and SE. I received numerous
helpful and informative replies, as well as some requests to post what
information I could gather. Here, then, is some of the information I
received:
************* from Dave Platt (dplatt@coherent.com) I learned:
#The analog board in the Plus (and 128 and 512) contains the power supply
#circuitry and the video drivers (actually they're closely interrelated).
#These are notoriously prone to failure... the Plus runs hot, and draws
#about as much current as the power-supply is capable of putting out.
#Common failures include overheating/drying of the 3.9 uF nonpolar
#capacitor, failure in the flyback transformer and its associated diode,
#and failure of the solder connections attaching various components,
#wires, and jacks to the PC board. The Plus really needs a fan of some
#sort to keep cool... used without one, thermal cycling can cause failure
#within a year or so. When this happens, the official Apple solution is
#a new analog board. [Edited Here]
#The original SE had a different problem... it does have a fan, but the
#fan is both noisy and tends to emit some EMI which makes the screen
#wiggle a bit. Once again, the Apple solution is a new analog board (on
#which the fan is mounted... the new fan is quieter and is magnetically
#benign). Apple was willing to do the board-swap for free, even out of
#warranty, if the SE had a bad case of the shimmies... or so I'm told.
[Edited Here]
#Dave Platt VOICE: (415) 493-8805
# UUCP: ...!{ames,apple,uunet}!coherent!dplatt DOMAIN: dplatt@coherent.com
# INTERNET: coherent!dplatt@ames.arpa, ...@uunet.uu.net
# USNAIL: Coherent Thought Inc. 3350 West Bayshore #205 Palo Alto CA 94303
************* From Jeanne Devoto (jdevoto@apple.com) I learned:*
#There are two main circuit boards inside a Plus or SE: the digital board
#(or "motherboard") and the analog board (or "power supply"). The power
#supply board also carries the circuitry which controls the built-in
#monitor.
#The Plus power supply was the same as in the original 128K Mac in basic
#design. There were some problems with it: it is somewhat less robust than
#is desireable in a machine with the power requirements of a Plus, it tends
#to overheat, and so on. Most power supply problems that I've seen are
#either a bad flyback transformer (I suspect there may have been a bad
#lot at some point, judging by the age pattern of failures) or to cold
#solder joints on the board itself. The latter problem can be fixed fairly
#easily by re-soldering the bad connections.
#Putting a fan in a Plus will prolong the life of the power supply, since
#some of its problems are due to the risks of overheating. [Edited
Here]
#Although the design of the SE is very similar to that of the Plus, its
#power supply was completely redesigned and is very robust. I wouldn't worry
#about your SE, unless of course you're having problems. Power supply
#failure in an SE is pretty rare.
--
#====== jeanne a. e. devoto ========================================
# jdevoto@apple.com | You may not distribute this article under a
# jdevoto@well.UUCP | compilation copyright without my permission.
#___________________________________________________________________
# Apple Computer and I are not authorized | CI$: 72411,165
# to speak for each other. | AppleLink: SQA.TEST
****************************************
There were a number of third-party repair options recommended as well,
and I will supply them to anyone who is interested. Nevertheless, in
order to keep from degenerating into a commercial, let me summarize the
technical aspects of repairing/replacing one's ailing analog board...
Robert Bauer (RBAUER@oregon.uoregon.edu), who works for one of the
third-party repair shops (Soft Solutions), explained that a common cause
of both power supply and video problems is the failure of the capacitors
and/or voltage regulators/rectifiers. The problem with heat has been
mentioned above, and compounding the problem are the components
themselves. Bauer wrote that "[Apple's] filter capacitors are all rated
at 1,000 hours, which is embarrassingly low..." and that their rating
is "35v and should be 100v." The solution his firm recommends is the
replacement of the original components with 'heavy duty' parts,
including "a 3.9uf @100 volts, 5000 hour capacitors, higher-amp
rectifiers, etc." This is something that the more adventuresome among
us can do themselves:
# If you can solder and aren't a klutz, the job jakes about an hour to
# two hours, most of that time spent double-checking your work.
As for my own machine, a late '87 SE with a fan that sounds like an
idling M-88, I've had no problems. The only report I received which
*did* mention problems with the SE power supply came from Walter Clinton
(amber@ucscc.ucsc.edu) who had to have the diodes in his machine
replaced.
Thanks for the help, everyone!
--HC Bowman