> good Mac's CRT. The reverse IS true, to a point -- with the 128k's
> flyback out of circuit, there is nothing to power the Horizontal
> circuit that comes after, so I get a Vertical line, but the CRT
Hold everything! You're barking up the wrong tree. If you are able to
see a vertical line, then the high voltage circuitry is working (and the
crt is getting the right voltages, more or less). And if the HV
circuitry is working, then the horizontal drive is working, so save
yourself the trouble of going component-by-component back to the horiz
input.
You have a horizontal deflection problem. Here are some possible causes,
in no particular order:
1) Bad solder joint(s) on the analog board, where the 4-pin yoke
connector is attached. Even if you can't see a problem, resolder *with
fresh solder* anyway. This is the *most* common cause of your problem.
2) Corroded/burned pins within the 4-pin connector.
3) Open 3.9uF (4.7uF in some macs) nonpolar electrolytic cap (the one
often held down by a mess of hot glue). This is a *very* common cause of
the symptom you are seeing.
4) Loose connections in the vicinity of that nonpolar cap (esp. of the
width adjustment inductor).
5) Defective deflection yoke (possible, but I have *never* seen this on
a 9" mac)
Again, if you can see the crt display anything (especially if it's
bright and in reasonable focus), then the HV circuitry is just fine,
because it needs horizontal drive to generate HV. Deflection is a
separate thing.
--Tom
--
Prof. Thomas H. Lee
Center for Integrated Systems, CIS-205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu
650-725-3709 voice, -3383 fax
--
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