Apple II Computer Info
one of the same (or slightly larger) uF value with the same (or larger) Voltage
rating. Size and shape are, also, important in order to get a good fit.
When removing the bad cap, be sure to mark the "+" side on the board-- use
the markings on the cap's cover to identify the "+" side. Install the replacement
cap with its "+" lead in the marked hole.
Note: Also see the C7 fix discussion in next Question.
Messed-up or 'Dirty' Adjustment
The power supply may have a mini-potentiometer mounted on the circuit board
for fine-tuning voltage output. Usually, it will be somewhere near the end
opposite the Switch and will have a slotted plastic 'knob'.
If there is such an adjustment, mark its current position and, then, turn it
back and forth. (If you have some Radio Shack, etc. 'Circuit Cleaner', into the
mini-pot first is a good idea.)
Set the adjustment a bit to one side of the original setting and plug in the
power supply. If it now seems to work the problem was a 'dirty' voltage adjustment
control.
Check the voltage on the +5V line with a meter and adjust it to 5 Volts.
(Note: _no_ output due to a dirty adjustment control seems unlikely. Incorrect
output is more probable; and, this could cause a IIe to not work.)
Beyond the above, you are, most likely, looking at a bombed electrolytic
capacitor which is not obviously bad or a blown main power transistor (the big
silvery thing mounted on a heatsink). Unless you enjoy more involved electronic
testing and repair work, your best course is, probably, to get a replacement power
supply.
____________________________
From: O Aaland
012- My Apple IIe fails to turn on! I have to turn its power
switch on and off several times and sometimes wait a long
time before it finally powers up!
If the power supply you are working on is an ASTEC brand the most common
problem is the 10V 220 uf capacitor located about 1 inch to the rear and left of
the transformer. I find this to be the cause in about 80 pecent of the ones I
repair. Use a 25V 220uf capacitor as a replacement and chances are real good that
it will not fail again.
----------------------------
From: Stephen Shaw
If you open the power supply up (WITH THE MAINS PLUG OUT!) you will find a
capacitor C7 near the transformer in the middle of the printed circuit board (a
220 uF 16V capacitor if I remember correctly) change it for a 220uF 25V 85 degree
Centigrade rated capacitor and it should clear the problem up.
----------------------------
From: Jeff Allen
Apple II Computer Technical Information : Apple II Family Hardware Info
ftp://ground.ecn.uiowa.edu/2/apple2/miscinfo/hardware : May 2001 : 405 of 572
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