[Coco] Re: Help: Magnavox 1CM135 Monitor

[peak at mail.polarcomm.com]

Boisy
Do everything just like richard batt says but do it with 
power off and monitor unplugged!! Also you might want to take 
a close look all over the flyback. If there are cracks in the 
flybacks plastick case or tiny wires sticking out the side 
where they souldnt be then nothing will help but replacing 
the flyback.

Good Luck
Eric 


---- Original message ----
>Date: Sun, 29 Feb 2004 12:46:30 -0500
>From: "Richard Batt" <dickbatt at buffalo.com>  
>Subject: [Coco] Re: Help: Magnavox 1CM135 Monitor  
>To: coco at maltedmedia.com
>
>Boisy:
>
>The most common problem on Magnavox monitors was cold solder
>joints on the flyback transformer.  Marty Goodman used to
>recommend resoldering all the connections on the flyback
>when you have this type of problem.  I had to do this on my
>Magnavox monitor, although I'm not sure if its exactly the
>same monitor.  However,I understand this was a common problem
>for most Magnavox monitors and small TV's.
>
>The big problem with working on this transformer is it is
>used to generate the high voltage for the CRT.  A CRT can
>hold a charge for many days waiting for some unsuspecting
>person to touch the wrong spot, and then ZAP.  It probably
>won't kill you, but it could, and it's definitely unpleasant.
>It's possible, since the monitor's not working, that there is
>no charge left, but you can't depend on that.
>
>If you are going to try repairing this, first discharge the
>high voltage circuit.  I use a long screwdriver with a 
plastic
>handle.  I hook a jumper wire with alligator clips on each 
end,
>one end on the screwdriver near the handle, the other end on
>the monitor chassis.  Someplace on the steel frame that 
every-
>thing's mounted to.  Then stick the tip of the screwdriver
>under the rubber shield that surrounds the wire that hooks to
>the side of the CRT.  Pry the rubber up enough so you can see
>underneath.  Touch the metal ring embedded in the glass of 
the
>CRT and the end of the HV wire where it hooks into the CRT.
>The CRT is what stores the charge, so if you get that 
discharged
>you should be safe.  You might touch the terminals on the
>flyback transformer where they come through the pc board just
>to touch all the bases.
>
>The flyback transformer is maybe 3 in. across and is mounted 
on
>the pc board that runs vertically.  I forget which side of 
the
>monitor its located.  However, the HV wire from the CRT runs
>either right to it or next to it.  The transformer is heavy
>enough that handling fractures the solder joints where its
>soldered to the pc board.  If you casually look at the solder
>joints they look OK.  But under a bright light and magnifying
>glass you may be able to see the cracks.  When the solder 
first
>cracks, everything keeps working because the broken parts
>are still touching.  But eventually the solder oxidizes (just
>like the tin plated contacts on disk controllers and other
>packs) and loses contact.  And stops working.
>
>Whether you can see cracks or not, I would recommend 
resoldering
>all the pins of the flyback transformer where they come thru
>the pc board.  Some of the pins are rather heavy, so you will
>need a fairly heavy soldering iron, heavier than one would
>normally use for normal pc board work.  Add a small amount of
>new solder to each joint, but make sure all the solder flows
>between the pin and board run.  If you get too much solder on
>a pin, solder suck it all off and start over.
>
>As this was a common problem, the odds are pretty good 
resoldering
>the pins will fix it, but of course, it could be something 
else.
>
>Hope this helps you out.
>
>Dick
>
>ps I went thru all my copies of Marty Goodman articles from
>Rainbow and did a quick check of articles in the hardware
>database from Delphi but couldn't find anything.  But I'm
>positive that Marty wrote up something about working on
>Magnavox monitors with this problem if you want to do some
>hunting, yourself.
>
> 
>Original Message
>------------------------------
>From: Boisy G. Pitre <boisy at ...>
>Subject: Help: Magnavox 1CM135 Monitor
>Newsgroups: gmane.comp.hardware.tandy.coco
>Date: Sun, 29 Feb 2004 10:21:03 +0000
>
>I have a Magnavox 1CM135 RGB/Composite Monitor - this thing 
was working 
>great, then all of a sudden stopped.  Now there is no 
picture.  Just a 
>constant, high pitch squeal when you apply power.
>
>Can any of you Monitor guys (Gene Heskett?) provide some 
insight as to 
>what possibly may be wrong?  I don't have much expertise on 
diagnosing 
>monitors, and before I pitch it to the curb, I want to make 
sure it 
>isn't something simple or easy to fix.
>
>Boisy
>
>
>
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