1 Nov
2012
1 Nov
'12
1:41 p.m.
I have a well-treated Macintosh SE/30 that I'd like to fix up.
Problem 1) Whenever the CPU is doing something or something is being read
or written, faint warbling screeches can be heard coming from inside. The
volume control does nothing to quell this noise.
Are you sure it's coming form the speaker? Desoldering the speaker, or
one connection to it, will quickly determine if that;'s the case.
Most of the time, such noises come from the PSU chopper transoformer, and
can be silenced by replkacing the high ESR cpaactiros in the PSU.
Problem 2) The image on the monitor is canted a few degrees clockwise --
enough to be noticable and irritating.
You need to rotat the defleciton yoke. Open th case amd then slacken the
clamp on the yoke. Often the yoke sticks in place, you do not want to
force it becasue you cna break the CRT. If it won't move, then take the
clamp right off and open the slots the clamp fitted over with a
screwdrier. That normally frees the yoke,. Refit the clamp, but loosly.
If you don't mind workign on HV stuff, power up, opld the yoke my the
plasticc former, and rotatie it to gt the pictutre straight. wathcout,
there are hgih voltag spikes on the horixotnal deflection winding.
If you are more cautious, work out roughtly waht angle to turn it by, and
do so, power up, and see if it's right.
When you have it in the right postion, retighten the clamp. Do not
overtighten it, particualrly in warm weather 9the clamp wil lcotnract in
cold weather, making it even tighter. The old 'advice' was 'Tighten until
the CRT implodes, then back off 1/4 of a turn' :-)> If in doubt, leave it
too loose, the worst that will then happen is that the yoke will move
again and you;'ll ahev to repeat the adjustment.
-tony