Path: utzoo!attcan!uunet!lll-winken!ames!mailrus!tut.cis.ohio-state.edu!VAX1!dave
From: dave@VAX1.CC.UAKRON.EDU (David Stoutamire)
Newsgroups: comp.sys.mac
Subject: Video problems
Keywords: video
Message-ID: <68@VAX1.CC.UAKRON.EDU>
Date: 12 Jan 89 19:58:10 GMT
Distribution: na
Organization: U of Akron, Computer Center
Lines: 29

I have in the past noticed quite a few postings concerned
with video and power supply problems on the Mac.  I
have a friend with an original (!) (being upgraded)
128K Mac on which I saw the screen slowly fade, shrink and
die.  It seems restricted to the video --- the machine
boots and will read disks etc. but just no video.  I have
enough experience to replace a component, use a volt meter
and so forth and would dearly love to save my friend some
$$$ here.  My questions are:

  1) What are the most likely suspects?  I have seen
     references to bad caps and flyback transformers.
     If any articles have been published I would appreciate
     being pointed in the right direction.

  2) Where can one get schematics for an original Mac?

  3) In upgrading (512K, new ROMs, double sided disk)
     can a new full capacity drive be added to the external
     drive port, ignoring the old internal one?  Can
     the new ROMs just be placed in the sockets of the old
     64K ones?  There would seem to be another address pin
     needed for 128K.

Responses to any of the above will be appreciated.  I have
seem many requests for these questions in the past, so I can
forward answers to anyone else with similar questions.

			 -= David Stoutamire =-