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Re: Dead GS, what to do?
SUPRDAVE writes ...
>
> i bought a GS for $5, but i'm getting nothing when powering on; no power light,
> no beep and no video. obviously its the power supply, but is there anything i
> can check or fix? i can verify the power going into the computer itself, but
> dont know what to check from there.
>
....
The info below should help. Good luck!
Rubywand
_______________________
from: Csa2 FAQs-on-Ground file: CSA2POWER.TXT rev007
ftp://ground.ecn.uiowa.edu/2/apple2/Faqs
....
1. Open the case and check inside for indications of Coke spills,
debris, etc.. If everything looks okay, continue on. If not clean away
the mess; it could be causing a short. After cleaning (and drying), turn
ON the power to see if the problem is fixed.
2. If there is a fuse socket, pull the fuse and check it. (If it's
blown, try replacing it. If the new fuse blows, replace it, pull all
Slot cards and try powering ON again. If the fuse does not blow, hop to
#7 below. If the fuse blows with no cards installed your best course is,
probably, to forget about repairs and get a replacement power supply.)
3. Unplug and replug the power cord at the point where it connects to
the IIe. Turn ON power. Try wiggling the power cord.
4. Substitute a power cord from a known-working IIe and turn ON power.
5. Turn ON the power. Jiggle the power switch. If the machine shows
signs of life, the switch is probably bad.
6. Open the case. Unplug and re-plug the Power Supply cable to the
motherboard. Turn ON power. If the machine seems to respond, try
cleaning the power supply plug and socket.
7. Pull all cards from Slots and turn ON power. If the machine 'comes
alive' one or more of your cards may have a short or may have been
cross-socketed. Clean the contacts on each card (e.g. with alcohol).
With power OFF, replug a card (be sure to line-up card and Slot
contacts) and turn ON power. Do this for each card. If a card causes the
machine to fail, it is, probably messed up. If no card produces a
failure the original problem was, likely, a card which was not properly
inserted.
If the above tries get you nowhere, remove the power supply from
the 'dead' machine and swap in one removed from a good machine.
(Removing power supplies is pretty easy.) If the 'dead' machine now
works you will know that the original power supply is, probably, bad.
----------------------------
011- What are some good Apple II power supply fix tries?
Apple II power supplies can often be repaired. The bother involved
varies considerably with the cause of malfunction.
Note: The following refers more or less directly to II+ and IIe
supplies; however, many of the ideas will work with the IIgs power
supply as well.
Bad Power Cord
Unplug and replug the power cord at the point where it connects to
the IIe. Turn ON power. Try wiggling the power cord. If the Power Supply
comes ON at any time, try substituting a power cord from a known-working
IIe. If this fixes the problem, you can be pretty sure that the problem
was a power cord with a broken wire.
Poor Power Supply Connector Connection
Unplug and re-plug the Power Supply cable to the motherboard. Turn
ON power. If the machine seems to respond, or responds when the
connector is wiggled, you probably have a dirty or loose connection.
Clean the power supply plug and socket with an alcohol swab. Using
long-nosed pliers slightly re-crimp the 'holes' on the socket (or,
insert a jeweler's screwdriver into the space between each hole and the
plastic casing and twist). The idea is to restore a firm grip for all
contacts.
Another possibility is a loose or broken socket solder connection
to the motherboard. The repair is to remove the motherboard and
re-solder the connections to the socket.
Bad Switch
It is fairly easy to identify a bad switch-- it will, usually, not
snap cleanly into position, feel crunchy, and/or have a burn spot. The
repair is to replace the switch with some AC power switch that will fit.
Or, you can permanently connect the switched lines and add an in-line
switch to the power cord.
Blown Fuse
Some power supplies may have a fuse. Open the power supply. Look
for a fuse mounted to the circuit board. If there is one, check it. An
Ohm meter can be used to check for continuity if it is not obvious that
the fuse is blown. If the fuse is blown, replace it.
Bad "Globar" Element
Look toward the end where the power cord is connected. Somewhere
close to the place where wires from the switch go to the circuit board
there should be a small disk-shaped component which is not a disk
capacitor. Probably, it will be black with no markings. This is a
"globar" resistor. Check it to be sure that it is not cracked and that
both leads are really connected to the disk.
If the globar element is broken or if a lead has popped off, you
will need to get a replacement from an electronics supply shop. (Tell
the shop person where the globar resister comes from and describe its
size.)
Blown Electrolytic Capacitor(s)
On the end of the circuit board near the Switch are some relatively
large electrolytic capacitors (typically these are tubular aluminum
things with shrink-wrapped grey or light-green covers on which there are
markings). Usually, they are the same size and have the same uF value
and Voltage rating. One (or more) of these may be obviously blown or may
just show some slime near the base.
If you find something like this, the suspect capacitor should be
replaced by 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
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. ....
----------------------------
From: 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.
____________________________
From: Rubywand
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.
____________________________
From: Mike Smith
014- My GS power supply seems to be nearly dead! The only odd
looking symptom so far is that one of the big electrolytic
capacitors near the power input side is at 260 volt & the
other is at 30 volt?!
There is a 100k bias resistor in the front end of the inverter. If
this resistor is broken, loose, or otherwise 'open' you will get the
symptoms described. Replace the resistor and both capacitors should be
at the same voltage ( approx 140 volt) and within the 200 volt working
rating of the capacitors. This should fix the power supply.