Fat Mac power supply failure

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Article #14601

#14601

From: abe
Date: Sat, 24 Jan 1987 00:18

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The high voltage power supply of my fat Mac went up in smoke about a week ago.
The smoke was produced by the failure of a silicon rectifier diode, CR1 (Apple
part G1854 8418).  After much trial and error I have replaced it with an
SK3925, which is an Si-Sw, Fast Recovery Damper diode.  It runs very hot.  An
SK9004, an Si Rectifier (3A 100 PRV) works as well (runs as hot).  Some of the 
inadequate trial replacements were Si Rectifiers with much higher voltage
and/or current ratings.  Some of them ran so hot they desoldered themselves.

I would like to know the proper replacement for CR1.  Does anyone know?

This is the second failure of CR1 I have observed.  A friend's fattened Mac
developed bad solder joints on CR1, which produced breakup in the display.  He
resoldered the joints and has had no problem since.  His first suspicion was
manufacture error, but I suspect it was a failure caused by overheating.

It appears to me that a cooling fan is in order.  I would appreciate any
recommendations.

Please reply via E-mail.  I will summarize significant replies.

	...!ihnp4!pur-ee!j.cc.purdue.edu!abe
	abe@j.cc.purdue.edu

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From: abe@j.cc.purdue.edu.UUCP
Newsgroups: comp.sys.mac
Subject: Fat Mac power supply failure
Message-ID: <3005@j.cc.purdue.edu>
Date: Fri, 23-Jan-87 19:18:38 EST
Article-I.D.: j.3005
Posted: Fri Jan 23 19:18:38 1987
Date-Received: Wed, 28-Jan-87 19:54:21 EST
Organization: Purdue University Computing Center
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