OStMichael

Q: Macintosh Performa 6400/180, distorted display problem, how to fix?

I have a Macintosh Performa 6400/180 connected to an Apple
Multiple Scan 15 Display Model Number M2943. When the computer is powered up, I
get a patchy looking, distorted display. I can see the floppy disk icon and the
mouse pointer when I move the mouse through the distortion. I can hear the hard
drive cycling with flashing of the activity drive led. Is the problem with the
computer or the monitor? I have 2 of these monitors, and getting the same
distorted display on both. What and where is the defected part(s) located? I am
an electronics technician and able to do circuit repairs. Thanks for your help.

 

 

Michael

 

 

Here is a picture of the display I am getting:

 

Macintosh Performa 6400-180 Problem.jpg

Macintosh Performa 6400/180

Posted on Aug 19, 2015 1:57 PM

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Q: Macintosh Performa 6400/180, distorted display problem, how to fix?

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  • by Kappy,

    Kappy Kappy Aug 19, 2015 2:01 PM in response to OStMichael
    Level 10 (270,831 points)
    Desktops
    Aug 19, 2015 2:01 PM in response to OStMichael

    Try replacing the internal battery.

  • by Jeff,

    Jeff Jeff Aug 20, 2015 1:50 AM in response to OStMichael
    Level 6 (11,559 points)
    Aug 20, 2015 1:50 AM in response to OStMichael

    One of the quirks with those Performas having a slide-out motherboard concerns oxidization that can develop on the gold-plated contacts/pins along the edge of the motherboard, compromising the connection they make when engaged in the main slot from which individual wires run to the DB-15 display port, the optical and hard drives, front panel audio and speaker, etc.  If the pins on the motherboard aren't making a good connection within the slot, you can experience odd problems with any of those items mentioned.  To correct this, you should remove the motherboard, lay it on a non-static inducing surface (like a newspaper), and then gently scrub the pins along the leading edge of the board (upper and lower sides) with a soft, white eraser.  Don't use a pink-colored pencil eraser.  They'll probably have a dark gold appearance before you begin, but will be much brighter/shiny afterward.  Be sure to blow off any residual rubber shavings, prior to re-installing the motherboard.  Reconnect everything and see if the problem has been eliminated.  The previous recommendation about replacing the motherboard's 4.5-volt alkaline battery is always a good one for those Macs.  Unlike most of Apple's computers of that period that used a 3.6-volt ½AA lithium battery (that rarely tends to leak), the alkaline battery in those Performas is notorious for leaking solution, after it has been dead for a while.  I've seen motherboards ruined by the corrosion left in the path of the leak.  A date that reverts to 1956 every time the computer is unplugged from AC power is a good indication that the battery is shot.