Apple II Power Supplies and Cooling
Csa2 FAQs-on-Ground file: Csa2POWER.txt rev012
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____________________________
001- What's the pin-out and load specs for the IIgs Power Supply?
002- Are the power supplies for the ][+ and IIe interchangeable?
003- What are the output capabilities of GS and IIe power supplies?
004- Can I use a 'generic' surplus power supply in my Apple II?
005- How do fatter leads reduce noise on the +5V & +12V lines?
006- Is there any more that can be done to eliminate glitches?
007- Is there a power supply upgrade kit for the Apple IIgs?
008- What kind of internal fan can I install in an Apple IIgs?
009- Why do so few GS power supplies have a fan installed?
010- Some of our classroom IIe's don't work at all. Is there a fix?
011- What are some good Apple II power supply fix tries?
012- Why does my Apple IIe fail to turn on?!
013- What does a rapid chirping noise on a GS power supply mean?
014- How do I fix a nearly dead GS power supply?
015- What is a "Buggie Power Supply"?
016- Do I need the metal shielding in my GS case?
017- My System Saver IIgs has gotten very noisy. How can I fix it?
018- My System Saver IIgs panel feels springy? Is there a problem?
From: David Empson
001- Does anyone have pin-out and current ratings info for
the Apple IIgs Power Supply?
7 - 5 Volts 0.25 Amps
6 -12 Volts 0.25 Amps
5 +12 Volts 1.0 Amps
4 + 5 Volts 4.0 Amps
3 --nc--
2 GND
1 GND
The Power Supply connector pins are numbered as above. When you are
sitting in front of the computer, pin 1 is nearest you. (i.e. pin 7 is
nearest to the back of the motherboard).
____________________________
From: Rubywand
002- Are the power supplies for the ][+ and IIe interchangeable?
Yes. The plugs are the same and the ratings are the same and they
look alike. Aside from, possibly, needing to add mounting holes for
particular models, you should be able to swap ][+ and IIe power supplies
whenever you wish.
----------------------------
003- Could someone compare the output capabilities of the GS and
IIe power supplies?
Okay. This is from information presented in GS and IIe manuals:
PS Connector Output Max. Output Current
Pin# (GS/IIe) Volts (GS/IIe)
7/6 - 5 V 0.25 Amps /0.25 Amps
6/5 -12 V 0.25 Amps /0.25 Amps
5/4 +12 V 1.00 Amps /1.50 Amps
4/3 + 5 V 4.00 Amps /2.50 Amps
2/2 GND
1/1 GND
----------------------------
004- Can I use a 'generic' surplus power supply in my Apple II?
Sure. Check out the power supplies listed in the JDR and Jameco
catalogs. Mainly, you are looking for a relatively compact switching
power supply which fits the following guidelines:
1- all four Voltages (+/- 5V and +/- 12V) are available
2- the power supply can be fitted into your Apple II
3- the +5 Volt output is rated at 5-10 Amps
4- the +12 Volt output is rated at 1.5-3 Amps
5- price is no more than $25
As more and more new surplus power supplies are dumped, part of
your shopping challenge is finding one which is _small_ enough to work
well with the Apple II. This explains the price guideline. If a unit
costs more than $20, the odds are pretty good that it's too big
physically or electrically.
Too big electrically? In general, power supplies need to be loaded
in order to do a good job of regulation. A 25-Amp output which is called
upon to deliver 1 or 2 Amps is more likely to exhibit problems with
feedback and regulation than were it asked to deliver, say, 5 or 6 Amps.
An Apple II with a few power-sucking Slot cards will work fine with many
PC power supplies; a base system with no cards could have problems
adequately loading some PC supplies.
Your best choice for an in-the-case replacement is likely to be
some $15.95 unit rated at a total of less than 125 watts which was
originally designed to power a printer, monitor, or portable PC.
Probably, it will be "open frame" with no case, switch, fan, or power
cord.
Installing a power supply unit-- i.e. one not specifically designed
for the Apple II-- inside your Apple II can involve a fair amount of
work. When I did such an install on our II+, the most time-consuming
part was fixing up a way to mount the On/Off switch and AC cord socket
in the usual power supply opening in the back of the case. (Mounting the
stuff on a small plastic panel set into the opening worked fine.)
The power supply board itself mounted nicely on spacers in the
space provided for the standard PS. Once the AC and various DC lines
were connected, the new PS came on-line without a hitch. Our II+ hasn't
had any power supply problems since.
----------------------------
005- Could you please explain how adding thicker wire will decrease
noise on the +5V and +12V lines? I received and installed
my new "Heavy Duty" A2 power supply and get the same results
with my Second Sight board as before-- it still locks up the
computer on boot-up.
Ohm's Law says: E = I x R. The Voltage drop across a resistance
equals the Resistance (in Ohms) multiplied by the Current (in Amps).
The leads coming from most A2 power supplies have a low
resistance-- less than an Ohm-- but, as a user piles on peripherals and
current increases, a wire lead's "low resistance" may suddenly prove to
be too high. For example, suppose the +5V lead coming from a GS power
supply has a total resistance of 0.2 Ohms. If the average current load
on the +5V line is 2 Amps, the voltage drop across the wire is 2 x .2 =
0.4 Volts.
If the PS regulation is set to hold the +5V line at +5 Volts (at
the PS end) then, in the above situation, you are running your GS at 5 -
0.4 = 4.6 Volts. The system may run fine even though your main supply
voltage is a little low.
Then, the user adds a ZipGSx accelerator, a RamFAST interface, a PC
Transporter, and/or a Second Sight board. Now, suppose average current
load on the +5V line goes to 3.5 Amps. Our +5V wire now drops 3.5 x .2 =
0.7 Volts. The system must now run with a main supply Voltage of 5 - 0.7
= 4.3 Volts!
Though the above analysis speaks only of average voltages, it is
easy to see that a system designed to work at 5 Volts will eventually
begin to malfunction due to the voltage drop across a skimpy +5V lead.
In fact, any actual computer system would be likely to experience
crashes long before the average, measured at-motherboard voltage got
down to 4.3 Volts.
A Volt-meter reading at the motherboard PS plug does not show
instantaneous spike voltages. Each time a circuit switches, there is a
change in current drain. Quite a few circuits are switched with each
clock transition; so, the change in current can be substantial at 1 x
and 2 x clock frequency. Other events, like turning ON a disk drive, can
also produce brief up or down shifts in current drain. Either way, you
have brief changes in voltage across the PS lead(s) through which the
current is drawn.
The brief voltage changes are called "spikes" because they are VERY
brief. The larger the current shift and the greater the resistance of
the PS wire, the higher the spike Voltage. Since these spikes are in
series with the circuits connected to the PS and since they are
difficult to eliminate via bypass capacitors, they propagate throughout
the system. They are a kind of "noise".
Even worse, as current draw increases and spike voltage increases,
at-motherboard supply voltage decreases. So, you have a 'double whammy':
the lowered supply voltage reduces "noise immunity" just when you need
it most!
At some point, noise spikes appear which cause latches, memory
IC's, etc. to switch state. If the latch is on a RAMfast, you may get a
disk read error. If a memory chip is affected, data will be corrupted,
program instructions may change, ....; in short, your computer is likely
to malfunction.
All of which, to be sure, is "bad enough"; but, evidently, there's
more. Piles of anecdotal evidence indicates that operating the power
supply under such high-noise conditions drastically curtails its life.
How many csa2 posts complain about GS power supplies that crater "for no
reason" after just a couple months? How many users seem to be on eternal
quests for a solution to PS woes?
Our current GS power supply is the one which came with the computer
when it was purchased in the Fall of 1986. The main difference between
our PS and the piles of blown units is that fattened leads were added
back when we upgraded to an accelerator board.
To 'close the loop': you want THICK, heavy-gauge power supply leads
because they have less resistance. Less resistance means that the
voltage drop or loss across the lead is smaller. Noise is reduced AND
noise immunity is increased. Another effect which usually goes
unmentioned is that voltage regulation also improves because the 'sensed
voltage' is closer to the actual at-motherboard voltage.
Perhaps, now, taking a good look at your new Heavy Duty power
supply, you can see why it has not cured your glitch problems. Very
likely it has heavier leads than your old PS; but, the new leads are not
heavy enough.
The PS leads which carry significant currents are +5V, +12V, and
GND. These are the leads which should be replaced with heavier gauge--
e.g. #14 or #12 gauge-- wires. (You need to replace just one of the two
GND leads.)
----------------------------
006- Fattening my GS's power supply leads greatly reduced system
crashes. Is there any more that can be done to eliminate
glitches?
Yes. There is another weak link in the power delivery 'chain': the
motherboard circuit traces supplying power to Slot boards are fairly
skimpy, especially on ROM-01 boards. A heavy power user, such as a
souped-up Transwarp accelerator board, in Slot 7 can produce significant
noise up and down the entire Slot 'backplane'.
The cure is to remove the motherboard and tack on #18 - #16 gauge
jumper leads. (See Question 007 for details.)
----------------------------
007- Does anyone here remember the Mac SE upgrade kit that included
18-ga wire, a bunch of new caps and other fun stuff, that
increased the computer's amperage and allowed more upgrades,
also fixed many problems? Is there a power supply upgrade kit
for the Apple IIgs that someone has constructed?
Okay; here is your very own
A2-2000 On-Line Power Supply Mods Kit!
Swapping-in fat leads is, technically speaking, a pretty simple
job. You pop out the power supply, open it, unsolder old +5, +12, and
Ground leads, solder in the new leads, close and replace the power
supply. The tricky part is what hackers call the "mechanics".
First, #12 or #14 gauge wire is not very flexible. Getting stranded
wire (instead of solid) helps. Probably, #14 gauge is more than fat
enough for all three leads. One case where #12 or #10 gauge may be worth
the extra trouble is the +5V lead.
Use wires colored the same as those you replace. On the standard
connector, the first two leads are Ground. Almost always, these are
black. Next, there is a space, then, in order +5, +12, -12, -5.
Depending on the bother involved, you can unwedge the wire bundle
where it passes through the supply case and remove the three old wires
(+5V, +12V, and one Ground wire). Or, you can just cut away each old
lead. Leave the -5V and -12V leads and one Ground lead alone.
Getting to the PS circuit board involves some work. After removing
the mounting bolts, you will have to scooch up the board in order to get
to the bottom side. This will be easier if the wire bundle has been
unwedged.
Another hurdle is soldering to the circuit board. Once the old
leads and excess solder are removed, you will probably find that the
holes are too small! A jeweler's screwdriver makes a good hand drill for
enlarging holes. (Drill from the circuit side. Be careful not to tear or
dislodge the printed circuit.)
The new leads should be routed through the unused fan slots. (If a
fan is attached, remove it. It's in the wrong place to do much good in
cooling your GS.)
Note: If you have a fan mounted to the PS and you wish to keep it, then,
it will be necessary to enlarge the original cable exit hole. A sheet
metal "munching" tool should let you do this without having to entirely
remove the PS circuit board. (Just be sure to catch all of the munched
pieces!)
When routing the leads be careful not to place a twisting force on
a lead where it is soldered to the circuit board.
To get to each spronger (contact) in the plug, press on it through
the slot on the side near the wire end. This pushes up a small retaining
tab so that pulling on the attached lead will pull out the spronger.
Cut off the old lead, clean the end, and solder on the new lead.
Press the spronger back into the plug. To avoid mixups, it's best to
complete the process for each lead before doing the next.
When plugging in the power supply, take time to shape and arrange
the wires to minimize stress on the motherboard.
Motherboard Mod
Fatter +5, +12, and Ground leads should protect you power supply
and reduce circuit noise.
If audio noise in your stereo card output and/or system bombing due
to noise glitches were problems, they may be eliminated. A lot depends
upon which cards you've installed, which slots they are in, and whether
your IIgs is a ROM-01 or ROM-03.
The motherboard circuit traces supplying power to each Slot are
fairly skimpy, especially on ROM-01 boards. A heavy power user in Slot 7
can produce significant noise up and down the entire Slot 'backplane'.
The cure is to remove the motherboard and run leads to a couple
Slots ...
First, flip over the motherboard and get oriented. Below is a
quickie sketch showing the Power Connector points as well as key power
pins for a Slot. The view is from the _Bottom_ with the _Back_ of the
motherboard facing you:
Bottom of Motherboard
Power Connector Socket Slot
X GND +12V (pin 50) X X (pin 1)
X GND X X
.
X +5V .
X +12V .
X -12V
X -5V X X
GND (pin 26) X X (pin 25) +5V
.... Ground Plane Area (plug shields, etc. connected here) ....
|
|______________ Back Edge of Motherboard _________________________
A good way to make sure you know what's where is to use an Ohm
meter to check Resistance from pin 26 (GND) to a metal plug shield near
the back of the motherboard. (Set your meter to Ohms X1. Touch one meter
lead to pin 26 and the other to a metal plug shield. Resistance should
read nearly zero. Reverse the leads and repeat the check. Again,
Resistance should read nearly zero.)
Repeat the check for R between pin 26 and the GND points on the
Power Connector socket. R should be nearly zero. Using a marker pen or
white-out, mark pin 26 (GND) on Slots 3 and 7. Also mark the GND points
of the Power Connector socket.
GND: On the bottom side of the motherboard, connect a Black #16 gauge
wire from one of the Ground points of the Power Connector socket to the
Ground plane area near the back of the motherboard. Run a short Black
#16 gauge wire from pin 26 of Slot 3 to the Ground plane; run a short
Black #16 gauge wire from pin 26 of Slot 7 to the Ground plane. (You may
need to scrape through green insulating lacquer to solder to the Ground
plane area.)
+5V: On the bottom side of the motherboard, connect two #16 gauge Red
wires to the +5V point of the Power Connector socket. Connect the other
end of one +5V Red wire to pin 25 of Slot 3; connect the other end of
the second +5V Red wire to pin 25 of Slot 7.
+12V: If you have any cards which are likely to draw heavily on the +12V
line, then, on the bottom side of the motherboard, run a #18 gauge White
wire from the +12V point of the Power Connector socket to pin 50 of the
Slot in which the card is normally located. Otherwise, just run an #18
gauge White wire from the +12V point of the Power Connector socket to
pin 50 of Slot 7.
Check your connections. One quick check is that the GND and +5V
wiring to Slots 3 and 7 should be Black, Red (moving left to right) and
Slots 3 and 7 should 'look the same'. Any +12V wire should be on the
same side of the Slot (i.e. the same column of pins) as GND. None of the
wires should be connected to a middle pin on any Slot.
Notes:
1. All wires are insulated.
2. When cutting wires, allow enough slack to permit routing each wire.
You want to avoid having a wire rest against pointy connections on the
motherboard. Route wires away from motherboard mounting holes and around
places where the bottom of the case supports the motherboard.
3. The case's bottom and back metal shields are something of a shorting
hazard. Replacing the motherboard is much easier if these shields are
popped out and ditched.
Once everything checks out, replace the motherboard taking care
that no wires are caught between a support point and the motherboard.
____________________________
From: Mitchell Spector
008- I would like to install an internal fan in an Apple IIgs. I
pulled a good looking fan from an old PC power supply. It is
an NMB "FLOW MAX" rated: DC +12V @0.14 Amps. Is this fan okay?
How do I connect it?
The voltage rating is fine, the amperage level should be fine as
well.
You can connect the fan to the two-pin connector near the back left
side of the motherboard. The pinout for the "Fan connector" is +12V and
Ground. The +12 is the pin closest to the powersupply, or the pin on the
left if you are facing the GS motherboard from the front end. Most fan
wires are color
coded, so the red wire goes to power and black to ground.
____________________________
From: Rubywand
009- Why do so few GS power supplies have a fan installed?
Most users depend upon System Saver GS to handle cooling because
the GS case is not designed to take advantage of an internal fan. With a
fan mounted on the power supply, you can, mainly, blow air around inside
the case. The fan is not much good for drawing in cool air from outside
or pushing hot air out.
Another problem is noise-- both the kind produced by a fan when its
bearings begin to go and electrical noise which degrades the quality of
sound output. The fan uses the +12V pins which are needed for simple
installation of a popular sound digitizer card. A fan mounted on the PS
case could prevent plugging long circuit boards into Slot 1 and,
possibly, Slot 2.
Perhaps, as Charles Plater seems to suggest, there is some reason
for an internal fan. Mounted on the power supply (which is the only
place a mounting point is available), a fan could blow some air into the
power supply. Supposedly, this could extend power supply life.
Still, many users have 11 year-old GS's with original power
supplies which continue to work fine with no internal fan.
Basically, a PS-mounted fan in a GS appears to be the cure for a
problem which has yet to be discovered.
----------------------------
010- Some of our classroom IIe's work fine; but, some don't work
at all. Do the power supplies need to be replaced?
If "don't work at all" means you plug in a IIe, flip ON the power
switch, and 'nothing happens', then ...
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.
____________________________
From: Stephen Buggie
015- What is a "Buggie Power Supply"?
It is an external power supply, usually a surplus PC unit, which
connects to the Apple II via a heavy-duty cable.
My IBM-style power supplies generate the same voltages (+5v, +12v,
-12v, -5v) as those required by the Apple II. But IBM-style power
supplies deliver 150-200 watts of power, more than twice the weak output
of the standard 60 watt Apple II power supply. Thus, problems
associated with weak power (screen freezeups, crashes) in the Apple can
be reduced or eliminated by using an IBM power supply on the Apple.
With a strong IBM power supply, you can fill all your interface
card slots or add extra disk drives without overloading the power
source.
Recently, I have offered these power supplies for Apple II:
IBM 150 watt power supply, soldered to 5 ft cable; choice of either
IIgs or IIe plug. $27.00 plus $5.00 UPS shipping ($8.00 shipping
to Canada)
or
Cable-only; connects to IBM power supply at power-points P8, P9, and
Molex-4. Allows you to connect the IBM power supply you already own to
an Apple II (Specify whether IIgs or IIe plug is needed). $14.00 plus
$3.00 priority mail; To Canada: US$4.00.
Above cables made with heavy duty wires (AWG-18, with 600v insulation;
color-coded. All power supplies and cables thoroughly pre-tested prior
to shipping.)
200 watt power supplies occasionally available at $3.00 extra cost, but
an extra 3-4 weeks must be allowed.
Eight page illustrated instruction manual sent with each order; also the
manual is available on self-booting text-file disk.
Faster service!
During the past month, users have had to wait 2-3 weeks from
payment to shipment. More power supplies have arrived, and I have
ordered the cable components in larger quantities, so through the
remainder of the summer I expect to ship the orders within 4-7 days.
Steve Buggie buggie@unm.edu
200 College Rd. (505) 863-7504 office
Gallup NM 87301 (505) 863-2390 home
____________________________
From: Joseph Lee
016- Does the metal R/TV interference shielding in my GS case matter?
I've done some testing. The Radio/TV interference shielding
mattered, at least for all the people around in my former dorm.
----------------------------
From: Rubywand
My tests were done in a separate dwelling (i.e. not an apartment,
dorm, etc.) and focused upon effects in our 'Computer Room'. Turning ON
the GS produces some interference with or without shielding and the
level seems to be the same.
One problem with R/TV interference is that its level and kind is
dependent upon many factors. For example, I can get virtually complete
elimination of GS-produced Radio station interference by simply turning
ON a printer connected to our PC!
Each user will have to weigh the trade-offs for his/her situation.
Removing the shielding eliminates a dust trap and improves air flow. It
is easier to pass cables through case slots; and, if you need to remove
the motherboard (to make repairs, add Slot jumpers, etc.), removing the
bottom shield removes a shorting hazard when the board is re-installed.
If you remove the lid and do not like the way Radio or TV reception
is affected, leave the shielding alone. If the result is acceptable,
scrap the shielding.
____________________________
From: Scott G
017- My System Saver IIgs has gotten really noisy. How can
I fix it?
It may be that the fan inside the unit is showing wear. The good
news is that replacing the fan is an easy and rewarding task.
I knew my fan was starting to die when it sounded like it was
wheezing during spin-up. The fan, a Sprite model SU2C7, uses sleave
bearings, whose lifespan is determined by the lubricating oil supply in
the bearings. When enough of the oil evaporates, metal will grind
against metal resulting in heat and resistance that cause the fan to
quickly lock-up. Better quality fans use ball-bearings, but Kensington
apparently used the cheapest component available. Even among the models
with sleave bearings, the SU2C7 is the least capable. It can only move
18 cubic feet of air a minute (half what a typical PC fan moves) and has
a 55,000 hour rating.
In looking for a replacement for my dying fan, I chose to use a
better model. The Sprite model SU2B1 has the same dimensions as the
SU2C7 used in the System Saver and is readily available from Digi-Key
corporation. It uses ball bearings for long life (the fan is rated for
73,000 hours) and can move 34 cubic feet of air a minute. The higher
quality is readily apparent: the replacement is currently noticeably
quieter than the original even though it is moving more air per minute.
To replace the System Saver fan, first make sure the System Saver
AC power cord is unplugged. Next, you will need to open the case.
Opening the System Saver case involves removing eight screws. You
can remove the foam weatherstriping along the periphery of the case to
expose the screws OR you can poke through/around the foam at each screw
hole. The screw access holes are arranged as shown in the following
diagram (bottom view of the System Saver):
FRONT
______________________________________________________________
| ________________________________________________________ |
| | | |
| | * | |
| | _____________ | |
| *| | | Screw holes revealed ------>|* |
| | | | after removing foam | |
| | | Fan | | |
| | | | | |
| | | | | |
| | |_____________| | |
| *| |* |
| | | |
| | | |
| | | |
| | | |
| | | |
| *| |* |
| | | |
| | * | |
| |________________________________________________________| |
|______________________________________________________________|
BACK
Once inside, the fan can be removed by unplugging the power cord
that connects it to the circuit board. A grounding wire that is
attached by a screw must also be removed. The fan itself is held to the
case by two screws. Once you remove the SU2C7, you can replace it with
the SU2B1. Now mount everything back together again with the screws.
Apply new foam weatherstripping if necessary.
The refurbished System Saver is now better than a factory new
model! Notice the difference in sound: a quiet hum rather than a load
rumble. If you have a lot of cards, you will notice that the inside of
the IIGS is a lot cooler too. An upgraded System Saver is a great way to
counteract accelerator instability caused by heat.
Sources and parts needed:
1) Part: Sprite model SU2B1 (Digi-Key Part No. CR103-ND)
Source: Digi-Key Corp. (1-800-344-4536/www.digikey.com)
2) Part: Foam weatherstripping tape (3/8th inch width, 3/16th inch
thick) Source: Home Depot (or a comparable hardware store)
----------------------------
From: Louis Cornelio
The fan I removed from my System Saver IIgs is the Comaire-Rotron
Sprite SU2C1-- 'C1, not 'C7. Actually, out of the case, it seems very
quite. Much of the noise seems to be rattle from contact with the
plastic case of the SS ...
I put down some foam weatherstrip along fan-case contact points and
that did the trick! I guess there was a bit of vibraction or something.
The fan is stil audible, but only slightly from the air.
----------------------------
From: Rubywand
Below are specs, ordering numbers, and prices for several possible
System Saver IIgs replacement fans. As you can see, the noise numbers
for the sleeve bearing fan models originally used in System Saver IIgs
are not bad. The catch is that the numbers are for new units before
bearing wear begins to increase noise. If you replace your fan, a ball
bearing model is recommended.
Digi-Key 800-344-4539
Mouser 800-346-6873
Newark 800-463-9275
cfm = cubic feet per minute of air moved
db = measure of noise produced (for a new unit); lower is better
Comaire-Rotron Sprite SU2C1 <SS Original> (Digi-Key #CR251-ND,
p.234 in Apr-Jun 1998 catalog)
3.14sq. x 1.64 20cfm 27db 6watts 115VAC sleeve bearing $25.38
Comaire-Rotron Sprite SU2C7 <SS Original> (Digi-Key #CR108-ND,
p.234 in Apr-Jun 1998 catalog)
3.14sq. x 1.64 18cfm 26db 6watts 115VAC sleeve bearing $25.38
Comaire-Rotron Sprite SU2B1 (Digi-Key #CR103-ND,
p.234 in Apr-Jun 1998 catalog)
3.14sq. x 1.64 34cfm 40db 11watts 115VAC ball bearing $35.88
Augusta Tubeaxial (Mouser #432-81552, p.229 in Fall 1997 catalog)
3.15sq. x 1.5 21cfm 26db 9watts 115VAC ball bearing $23.63
Augusta Tubeaxial (Mouser #432-81554, p.229 in Fall 1997 catalog)
3.15sq. x 1.5 26cfm 31db 9watts 115VAC ball bearing $23.63
Augusta Tubeaxial (Mouser #432-81558, p.229 in Fall 1997 catalog)
3.15sq. x 1.5 32cfm 38db 10watts 115VAC ball bearing $23.63
NMB Peewee Boxer type 3115FS-12W-B10 (Newark #46F5098,
P.405 in 1998 catalog)
3.1sq. x 1.5 22cfm 36db 6watts 115VAC ball bearing $11.42
NMB Peewee Boxer type 3115FS-12W-B20 (Newark #46F5097,
P.405 in 1998 catalog)
3.1sq. x 1.5 27cfm 40db 7watts 115VAC ball bearing $11.42
NMB Peewee Boxer type 3115FS-12W-B30 (Newark #46F5096,
P.405 in 1998 catalog)
3.1sq. x 1.5 32cfm 44db 9watts 115VAC ball bearing $11.42
____________________________
From: Rubywand
018- My System Saver IIgs front panel has started to feel more
springy? Could this be a problem?
Yes. It indicates the plastic may be becoming brittle and that
supports behind the panel are weakened or broken. Some 'springy panel'
users report pressing on a switch and poking a hole in the panel!
Prolonged exposure to sunlight and/or long exposure to heat from
the GS are the usual causes. Preventative measures are to keep your GS
away from sunny windows and to increase airflow through the System Saver
for hot running systems. The easiest way to achieve the latter is to
swap in a fan with a higher cfm rating. (See fans listed in the previous
answer.)
Panels which feel very springy should be reinforced. Open the case
and used epoxy to reinforce panel and switch supports.