17.012 My Apple IIe usually 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!
Description
This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
17.012 My Apple IIe usually 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.
By: O Aaland
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By: 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.
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By: Jeff Allen
I've been trying to fix several dead Apple II power supplies from a local
school and have managed to bring back one from the dead now. The fix was to
replace the 10V, 220uF electrolytic cap with a new one. (I used a 35V piece).
Assuming that the board markings are useful, this was C7, on an Astec board
with the datecode "T8312" on it. I'm curious if anyone else that has replaced
that cap has noticed any browning of the pc board where the leads enter from
that 27ohm 2W 'R4' beast. ....
----------------------------
By: Rubywand
Very interesting! A bad C7 would screw up the regulator's feedback
voltage.
Even better, Jeff Allen's observation of the heat spot on the PCB seems to
indicate that heat from the nearby 27 Ohm power resistor is responsible for
shortening C7's life. If there is some way to eliminate this hot spot-- e.g.
using a 10W resistor, perhaps with a heatsink attached, or mounting the
resistor on the power supply's metal case-- many II+ and IIe power supply
crashes might be prevented.
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