Power Supplies & Cooling. .
..
...
Power Supplies & Cooling.
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001- What's the pinout 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- What are some good Apple II power supply
fix tries?
011- Some of our classroom IIe's don't work at
all. Is there a fix?
012- Why does my Apple IIe often 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?
019- Can an overloaded power supply affect IIgs
sound?
001- Does anyone have pinout 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).
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 MPJA, JDR, Jameco, and
similar catalogs (see http://home.swbell.net/rubywand/A2FAQs3VENDORS.html
for links). 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
* Except for PC power supplies, good four-output models with a -5V output
seem to be rare. You can add a simple -5V regulator circuit to the
-12V output
to obtain -5V.
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
$10-$15 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.
From: Rubywand, Marvin Miller, Michael Mahon
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.
The leads coming from most Apple II power supplies
have a low resistance--
much less than 1 Ohm. (Thanks to Michael Mahon for driving home this
point!)
Even so, as a user piles on peripherals and the current load increases,
a wire lead's
resistance may prove to be too high to allow maintaining proper operating
voltages
and low system noise-- e.g. you routinely get "FATAL SYSTEM" errors.
A good indicator of power problems is a noticeable
drop in voltage on the +5V
line as measured on the motherboard. Instead of the 4.9V - 5.0V typical
for a light
load, it will be 4.7V or lower.
Measurements and experiments with standard
IIgs power supplies indicate that
the actual DC voltage drop through the 18 gauge +5V and Ground leads
is only
(approximately) a total of 0.04V at 3Amps, which is what a moderately
"loaded"
IIgs system will draw. The explanation for getting a drop of 0.2V -
0.4V or greater
appears to be power supply regulation error. Some standard (and "heavy
duty")
Apple II power supplies with 18 gauge leads will hold at-motherboard
voltage to
around 4.9V at 3-4 Amps and some won't.
It is easy to see that a system designed to
work at 5 Volts will eventually begin
to malfunction as the available voltage drops by half a volt or more.
In fact, any
actual computer system would be likely to experience crashes long before
the
average, measured at-motherboard voltage got down to 4.5 Volts.
A voltmeter reading at the motherboard does
not show instantaneous spike or
"noise" voltages. Each time a circuit switches, there is a change in
current drain.
Quite a few circuits are switched with each main system clock transition;
so, the
change in current can be substantial at 1 x and 2 x main 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 power
supply and its leads.
The brief voltage changes are called "spikes"
because they are VERY brief.
The larger the current shift and the greater the effective resistance
of the power
supply plus its leads, the higher the spike voltage generated. 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.
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 IC 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 is bad enough; but, there may
be another negative affect when
noticeable system noise appears 'across' the power supply. 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? Reducing the noise may significantly extend the life of your
Apple II
power supply.
Power supplies with noticeable regulation error
often benefit greatly from
heavier leads, especially for +5V and Ground. Reducing the actual drop
through the lines reduces the resulting error; and, at-motherboard
voltage is
back to 4.8V or better under high loads. The heavier leads also reduce
noise.
Whether or not tighter regulating power supplies
benefit significantly from
swapping in heavier leads is an open question. At high switching frequencies
the
power supply's leads will have a higher effective resistance and the
spike
voltages appearing across the power supply output will be larger. If
you notice
otherwise 'mysterious' system glitches despite having a good, solid
looking
power supply and/or that power supplies tend to crater when connected
to
your Apple II, swapping in heavier leads may be a good idea.
Our current GS power supply is the one which
came with the computer
when it was purchased in the Fall of 1986. Yes, our GS was plugged
into a
System Saver IIgs fairly early on; but, then, line deglitchers have
been a nearly
universal accessory since the mid-1980's. The main difference between
our
power supply and the piles of blown units is that fattened +5V, Ground,
and
+12V leads were added back when we upgraded to an accelerator board.
Despite having also added a Focus Hard Card drive, RamFAST SCSI
interface, and a couple other boards, system crashes are very rare--
perhaps
one every 8-10 sessions (and those usually relate to a fault in the
software).
The 'bottom line' is that, so long as the power
supply is not actually defective,
real world experience supports fattening at least the +5V and Ground
power
supply leads as a major step in curing crashes due to system noise.
(See also
Marvin Miller's GS WorldView article: "I
Did the IIgs PS Mod, and the glitches
are gone!".)
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.
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- 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.
Note: Unless otherwise indicated, power should be turned OFF.
A Short
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.
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.
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 resistor 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 fix in the next Q&A and the C7 fix discussion
in Q&A 012.
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, a blown resistor (which may be
easier to
spot), 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.
011- Some of our classroom IIe's don't work at all. There is no
beep and nothing on the monitor. Do the
power supplies need
to be replaced?
Maybe not. My experience with a couple Australian
Platinum //e's indicates
that you may be able to repair the power supplies.
The power supply in the //e's I fixed is made
by Dyna Comp, Inc. for Apple,
model no: 699-0136. Ratings are as follows: Input 240V/50Hz, Output
+5V/4A,
+12V/1A, -5V/.25A, -12V/.25A.
Measuring the voltages on the //e motherboard I get
+ 5V = +1.3V
+12V = +2.8V
- 5V = -4.3V
If I disconnect the power supply connector from the motherboard and
switch it
back on, I measure the correct voltages on the connector.
The fault is caused by one or two failed 1uF
35V 85deg small electrolytics.
The location of each is as follows:
o- 103mm (4.1") from the back, and 27mm (1") from the left of the circuit board
o- 163mm (6.4") from the back, and 10mm (0.4") from the left of the circuit board.
I checked each of the ones I removed. they measured less than .05uF.
The fix is to replace each capacitor with a
1uF 35V or higher rated electrolytic--
if there is no "+" indication on the circuit board, mark the plus side
before removing
the old capacitor. I used 1uF 50V 85deg as that's what was in my parts
bin. (You
may need to clean up some gunk leaked onto the board by the old capacitors.)
From: Stephen Shaw
These are called "kickstart capacitors" in
switched mode power supply technology
(SMPS) circuit descriptions. If you ever get an SMPS in with tripping
or low output
voltage or amperage, change all small value electrolytic capacitors
(below 330uF and
35v) with high temperature capacitors (105 degree centigrade).
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.
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.
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.
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.
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)
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
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.
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)
Note: Check below for other fans that will work.
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: Shaun Olson, 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.2138 in Sep-Dec 2007 (T073) catalog)
3.14sq. x 1.64 (80x42 mm) 20cfm 27db 6watts
115VAC sleeve bearing $27.50
Comaire-Rotron Sprite SU2C7 <SS Original> (Digi-Key #CR108-ND,
p.2138 in Sep-Dec 2007 (T073) catalog)
3.14sq. x 1.64 (80x42 mm) 18cfm 26db 6watts
115VAC sleeve bearing $26.80
Comaire-Rotron Sprite SU2B1 (Digi-Key #CR103-ND,
p.2138 in Sep-Dec 2007 (T073) catalog)
3.14sq. x 1.64 (80x42 mm) 34cfm 40db 11watts
115VAC ball bearing $29.00
Sunon AC Axial Fan SF11580A-1083HBL.GN (Digi-Key #259-1379-ND,
p.2130 in Sep-Dec 2007 (T073) catalog)
3.15sq. x 1.5 (80x38 mm) 24cfm ??db 14watts
115VAC ball bearing $16.36
ADDA AC Fan (Mouser #664-AA8381HB-AT-LF, p. 1716 in 2007 catalog)
3.15sq. x 1.5 (80x38 mm) 24cfm 25dB 9watts
115VAC ball bearing $14.08
ADDA AC Fan (Mouser #664-A8038MBT-110LF, p. 1717 in 2007 catalog)
3.15sq. x 1.5 (80x38 mm) 24cfm 25dB 6watts
115VAC ball bearing $14.08
Orion OA80 Series Fan (Mouser # 670-OA80AP111WB, p. 1730 in 2007 catalog)
3.15sq. x 1.5 (80x38 mm) 31cfm 29dB 12watts
115VAC ball bearing $12.00
NMB 3115FS Series 3115FS-12W-B10-A00 (Newark #58K3033,
p.1476 in 2008 catalog (#125))
3.1sq. x 1.5(80x38 mm) 22cfm 36db
6watts 115VAC ball bearing $18.30
NMB 3115FS Series 3115FS-12W-B20 (Newark #68K1212,
p.1476 in 2008 catalog (#125))
3.1sq. x 1.5 (80x38 mm) 27cfm 40db
7watts 115VAC ball bearing $18.30
NMB 3115FS Series 3115FS-12W-B30 (Newark #58K7893,
p.1476 in 2008 catalog (#125))
3.1sq. x 1.5 (80x38 mm) 32cfm 44db
9watts 115VAC ball bearing $18.30
Comaire-Rotron Sprite SU2C1 <SS Original> (Newark #84K0240,
p.1473 in 2008 catalog (#125))
3.14sq. x 1.64 (80x42 mm) 20cfm 27db 6watts
115VAC sleeve bearing $32.78
Comaire-Rotron Sprite SU2C7 <SS Original> (Newark #77B7043,
p.1473 in 2008 catalog (#125))
3.14sq. x 1.64 (80x42 mm) 20cfm 26db 6watts
115VAC sleeve bearing $41.07
Comaire-Rotron Sprite SU2B1 (Newark #83K4218, p.1473 in 2008 catalog
(#125))
3.14sq. x 1.64 (80x42 mm) 34cfm 40db 11watts
115VAC ball bearing $32.92
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
use epoxy to reinforce panel and switch supports.
019- Can an overloaded power supply affect IIgs sound?
Yes, it can, even when the computer seems to be working
okay otherwise.
When I first plugged in my new TDX Stereo Card, I got sound, but very,
very
quiet. When I turned up the speakers (a *LOT*), the audible noise from
the
bus got almost deafening, yet the music level increase was barely perceptible.
It was at this point that I recalled why I bought
a Buggie power supply in the
first place. I had never needed it, having suffered no major power-starved
related
problems in the past; but, thinking it might make some small difference,
I removed
the internal power supply and connected the Buggie and tested again.
I have never, ever heard something sound so sweet!
It balanced the volume
perfectly and completely eliminated the bus noise.
