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From: gordon@milton.u.washington.edu (Gordon Davisson)
Newsgroups: comp.sys.mac.misc,comp.sys.mac.hardware
Subject: Re: Help!, my analog board is shot
Keywords: analog board, transformer, plus
Message-ID: <4985@milton.u.washington.edu>
Date: 12 Jul 90 05:39:09 GMT
References: <1990Jul11.194216.1939@cbnewsk.att.com>
Organization: University of Washington, Seattle
Lines: 32

In article <1990Jul11.194216.1939@cbnewsk.att.com> baz@cbnewsk.att.com (Bruce Zenel) writes:
>   I need some hardware help.  I turned on my Mac Plus today and all it did
>was click.  No beep, no screen, it just repeatedly clicks.
>   I have a feeling that it is the flyback transformer, which I've read about
>in the past.
>   Is there any way to replace this myself?  Is there a replacement
>transformer that I can buy somewhere?  I have no problem with desoldering
>a piece and putting in a new one.  Every Mac shop I have talked to today wants
>to replace the whole analog board, which is a real waste.
>   Any help would be appreciated.

It probably isn't the flyback.  Flybacks don't fail nearly as often as
their reputation would suggest, and when they do, they usually don't
cause the symptom you describe.  The ticking you're hearing is the power
supply resetting itself due to incorrect loading.  The most common fail-
ures that leads to this symptom are the GI854 diodes at board locations
CR1 and CR5; they tend to short themselves out, and overload the power
supply.  You can test for this by pulling the diodes and looking at them
with ohmmeters (be sure to remember which way around CR1 goes).

You can get repair parts (diodes, flybacks, and pretty much anything else
you'll find in a Mac) mail order from Soft Solutions:

	Soft Solutions
	907 River Road, Suite #98
	Eugene, OR 97404
	(503) 461-1136

--
Gordon Davisson
Westwind Computing	(206) 632-8141
4518 University Way NE, Suite 313, Seattle WA 98105