68kMLA Classic Interface

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Mac Plus distorted image

Posted by: tattar8 on 2015-11-02 19:21:51 I recently acquired (for a good price) a Mac Plus, that looks like it hasn't been touched for a while.  When I went to power it up, I noticed that the CRT was displaying a distorted image (see image).  However, the distortion mostly disappears after a while, and is only visible at the highest brightness.  It also seems as if the brightness doesn't remain stable, wavering slightly all the time. What might be the cause?

Posted by: unity on 2015-11-02 20:33:56 I would reflow all the connector solder joints. Including the set on the logic. VERY common failure point and the first thing I do before I even power one up.

Posted by: tattar8 on 2015-11-03 09:24:54 Got a link to some more info on reflowing joints?

Posted by: unity on 2015-11-03 10:06:00 No, just reflow them. Just look at the board and where ever a connector is, reflow. The flyback transformer too. Then just hunt down any others. I even found cracked solder at the power switches on some. Pretty straight forward and one does not even have to remove the board. Just pull the case back.

Posted by: techknight on 2015-11-03 13:36:35 This is actually discussed in the dead mac scrolls book.  This is caused by a diode, or possibly the flyback itself.

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