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Re: power supply apple IIe
Rudi Carael writes ...
>
>
>
> --
> Hi,
>
> I've got an Apple IIe with the power supply broken.
> It's making a sissing sound.
> Does someone have an electric scheme or a parts list for this power supply?
> or now where I can find it ?
>
> Thanks
>
> Rudi.c
>
> rudi.carael@skynet.be
A sissing sound may not be all that bad. Could be a bad switch or a cracked
"globar" resistor or some other cracked resistor. (Or, it could be a bad
electrolytic capacitor; but, those usually don't siss too long.)
Here is some more information which may help:
>>
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 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 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. ....
<<
(ref: Csa2 Apple II FAQs file Csa2POWER.txt)
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Rubywand