On 19-jan-06, at 1:31, Martin Swartz wrote:
Hello, all - In a previous (business) life I did a lot of support / hacking around with Macs, mostly 1xx Powerbooks and the SE series. Those days are gone. Now I have several questions to ask that relate to Classic Macs as restoration projects. In the corporate days, any one-piece Mac with flaky or failed video was scrapped out. Today I have a Color Classic that exhibits a working but shrunken video image. I've seen conflicting opinions about what can cause this, ranging from "cathode ray tubes do this when they get old" over to "the high voltage circuitry is going bad, not the CRT per se". What's the prevailing wisdom among this group? Can the analog circuitry be tweaked? Does someone build "new" replacement analog components for a reasonable price? Or is the answer "none of the above"?
most of the times a shrunken size is caused by a broken capacitor. the capacitor could be short circuted or not connected. I suspect a electrolyth (the big ones) if the aspect ratio of the image is still ok (3:4) then this may be in the power section of the analog board. if it is only in one direction then look in the horizontal or vertical deflection sections. Measure in any way the voltage of the power supply and check with the service manual. because you still get a picture there wont be a transistor broken. look visually for burned resistors and check the capacitors in the neighbourhood. a visual good capacitor could still be malfunctioning.
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