17.013 To my horror, this morning when I flipped my GS ON it emitted a rapid chirping noise (maybe 8-10 times a second) and refused to start!?
Description
This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
17.013 To my horror, this morning when I flipped my GS ON it emitted a rapid chirping noise (maybe 8-10 times a second) and refused to start!?
The chirping usually means that the PS load-detect circuit thinks that the
load is too great (i.e. that it draws too much current) or that there is an
'open' in a major output line (i.e. that there is, practically, no load at
all).
This can mean that the power supply is bombing and, so, almost any load is
too great. It may, however, mean that a short has developed on the motherboard
or on a Slot. It can, also, mean that a break has developed somewhere in the
+5V line or at the connection of the connector to the motherboard.
One test is to unplug the power supply, remove it, and do some load tests.
(Note: If the PS has a slotted adjustment pot, mark its position and, then,
turn it back and forth in case it has become stuck at a dead spot on the
control.)
If the PS can deliver +5V with a 3 Ohm power resistor connected across the
+5V and Ground lines, +12V with a 15 Ohm power resistor connected across the
+12V and Ground lines, and correct Voltage for -12V and -5V lines into, say,
100 Ohm resistors, then the PS is likely to be okay.
If the PS starts to chirp when even small loads are applied (e.g. 10 Ohms
across the +5V output), then it has one or more bad components or is badly off-
adjustment. If it has an adjustment, try cleaning the control and retry the
load tests after a small change in the adjustment setting.
If the chirping persists, replacing the unit with a new A2 power supply, a
module from Jameco, etc. or a Buggie external PS may be the easiest cure.
By: Rubywand
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