Info-Mac 1992 August/info-mac-1992.iso/Report/Mac Plus Dead Screen.txt

Internet Message Format | 1992-08-28 | 8KB

Date: Tue, 24 Mar 1992 10:20:50 -0700
From: [e-mail]
Subject: mac-plus-dead-screen.txt


  A few weeks ago, I sent out a query asking for information on Macintosh
Plus screen problems.  We had three Mac Pluses whose screens were black
with a thin vertical line through the center of the screen.  In response to
my query regarding Mac Plus screen problems, I received the following
messages.  They all center around the power supply as the problem, and in
particular the horizontal deflection capacitor.  The capacitor mentioned in
these messages turned out to be the problem on all three of our Mac Pluses
whose screens did not work.

     - Brad Stone
       Computer Support Coordinator
       Brigham Young University

[e-mail]

---Moderator, Please cut here and archive as
mac-plus-dead-screen.txt--------

From: [e-mail]
Subject: Mac Plus Screen problems
To: [e-mail]
Message-id: <_6_Mar_92_11:46:[e-mail]>
Via: UK.AC.GLASGOW.VME ; (to uk.ac.edinburgh.emas-a) 06 Mar 92 11:47:10 gmt

Hi Brad,

I have experenced similar problems here.
The problem is that the machines have lost there vertical sweep. I
purchased
a book entitled  "Macintosh repair & upgrade secrets" by Larry Pina,
published by Hayden Books, there address is 11711 North college, suite 141,
carmel, IN 46032 USA.
This book gives a step by step guide on how to repair and upgrade Macs from
a
128K Mac (remember them??) to a Mac SE.  It gives you the details of the
most
common problems encountered on the mac hardware side and the replacement
part
you require to fix your problem.


Hope this has been a help
David Edmondson
Glasgow University.

PS the International Standard Book Number is 0-672-48452-8
   the Library of Congress Catalog Card Number is 89-63715

=-=-=-=-=-=-=-=-=-=-

Date: Sun, 8 Mar 92 02:14:05 EST
From: [e-mail]
Subject: Mac Plus Monitor Problem (Q)
To: [e-mail]
Message-id: <[e-mail]>

Brad,
The fault is a failed capacitor in the Horiz deflection circuitry.
In particular it is C1 (I think that is the right designation for the US
model, It is for the Aust model) which is a 3.9uF non-polarised HIGH
FREQUENCY electrolytic capacitor, located near the upper left corner of the
analogue board
(right alongside the horiz deflection choke {inductor}).

In a mac plus, they tend to get rather warm and dry out ... leading first
to
a shrunken width, then a vertical line then to nothing! Often they will
show signs of rupture of the to of the capacitor case.

REPLACEMNTS:

A.

Use a HIGH FREQUENCY NON POLARISED electrolytic cap preferably rated at
100Volts.
(Larry Pina in his book gives Nichicon as a manufacturer. In Oz they are
branded Nippon CHem corp).
Ordinary electrolytics are NOT acceptable as they cannot
1.) take the AC currents  hence need for non polarised type
2.) Handle the high frequency (~15Khz) ... most electolytics exhibit a
little
    too much inductance! at thse freqs
3.) handle the ripple currents as the full horiz defl current flows in this
    capacitor. Most caps are good for about 500mA, the proper cap will take

    about 2.5Amps
The result will be failure .. often with much heat, steam and noise!


or

B.
A metallised polyester capacitor rated at about 4uF and 100Volts


I suspect that any good electronics parts supplier would stock suitable
capacitors. In Aust I paid about $1.50 each for the replacements ... beats
the otherwise standard Apple anaolgue board exchange costing about $A170
here.

regards
Joe Miles
Forestry Dept
Australian National University
Canberra                                    email: [e-mail]
Joe Miles                             email: [e-mail]
Forestry Dept  ANU                    tel:   [phone]

=-=-=-=-=-=-=-

From: [e-mail]
Subject: RE: Mac Plus Monitor Problem (Q)
To: [e-mail]
Message-id: <[e-mail]>

>  We are now trying to find a replacement
>capacitor.  So far we have not been able to find an exact replacement at
>one of the local electronics shops, but we are going to try again using
>your suggestion of a metallised polyester capacitor.


Brad,
I emphasise that you get the correct electrolytic or polyester cap.
It is the high ripple current which they must carry. Most caps have
an internal resisance which although small (yes, capacitors doo have
resistance too! :)  ),
 is sufficiently large to cause lots of internal heat to be generated. The
correct ones have a MUCH lower internal resistance.

In a real pinch, I have got away with using non-polarised speaker crossover
capacitors to do the job, but look for one that is about the same PHYSICAL
size as the orig failed component.
In the capacitor world, for capacitors of the same uF rating, larger
physical
size tends to be correlated wi higher current carrying capacity.


By the way, a computer repair shop may be able to help with supply as most
computer monitors (but not most tv sets) use this sort of horiz defl.
circuitry and use these types of capacitors.


good luck
Joe Miles                             email: [e-mail]
Forestry Dept  ANU                    tel:   [phone]

=-=-=-=-=-=-

Date: Fri, 6 Mar 92 10:55:48 EST
From: [e-mail]
Subject: Fixing Mac Pluses
To: [e-mail]
Message-id: <[e-mail]>

Buy Larry Pina's Book "Macintosh Repair and Upgrade Secrets".  You'll be
glad
you did.  BTW, for your needs, don't buy his new book "The Dead Mac
Scrolls".
The new book covers all Macs but in a much less detailed way.  The "Repair"
book leads you through the repair process for compact Macs (like the Plus)
step by step.  I've fixed dozens of Pluses using the info in this book
alone.  If you can solder, you can repair Pluses.  Good Luck.

Paul

PS: the best source of parts I've found is Soft Solutions [phone].
They even sell the book at discount.

___         Paul W Baim                    |  Internet: [e-mail]
|  \  \     Atlantic Aerospace             |  Compuserve:
72357,2315(rarely)
|__/__/     470 Totten Pond Road           |
|     \     Waltham MA 02154 USA           | "A leading authority is anyone
| \/\/ |    [phone]                 |  who has guessed right more
than
|_____/                                    |  once"  -- Frank A Clark

=-=-=-=-=-=-

From: Maslin William <[e-mail]>
Subject: Mac Plus video problem
To: [e-mail]
Message-id: <[e-mail]>

Brad:

What you describe is certainly a power supply or video problem. It could be
a
dead flyback or could simply be a cracked solder joint or bad capacitor. If
you
are interested in fixing the Pluses yourself (and saving big bucks over
having
Apple do it), the first thing you need is Larry Pina's book, *Macintosh
Repair
and Upgrade Secrets*. My copy is at home right now so I don't have the ISBN
number, but I'm almost sure it is published by Sams. Its list price is
about
$33 but I got mine from MacWarehouse for $27 plus $3 shipping, and it was
delivered to my door the next day. BTW, it also includes a disk for
aligning
the Mac.

Soft Solutions, 907 River Road, Suite #98, Eugene, Oregon 97404 (503)
461-1136,
Fax [phone] sells a variety of Macintosh parts and has a very good
reputation. Plus power board upgrade kits, including the flyback
transformer,
are $51 plus shipping. For $115 they will fix and upgrade the board for
you.
They also sell Pina's book ($27) and accept VISA and Mastercharge. They are
VERY friendly and helpful. I bought a MacRescue board from them about a
month
ago and was very satisfied with the service.

MicroDoc Computer Repair, 2477 West 29th Ave., Eugene, Oregon 97405 (503)
344-5335, Fax [phone] also sells Mac parts and upgrade kits. About a
year ago, I bought the Plus powerboard upgrade kit from them. All the parts
were of good quality and everything worked fine. Their parts prices seem to
be
significantly lower than those of soft Solutions' (the same upgrade parts
were
$39 plus shipping/COD). However, as far as I know, they only sell by COD.

I hope this helps you. Let me know if you find any other inexpensive and
reliable parts sources.

Bill Maslin CVM Mississippi State U.