The Meanwell RQ-85B PSU installed in my enhanced IIe in my last project is
humming happily thus far, so I decided to dig out my other two platinum IIes to
do the same since I find it difficult to trust those 30-year-old power supplies
inside them.
Problem - Simple But Only Functional
After
playing around with my enhanced IIe for a few months, I realized the dangling switch and power
connector at the back is functional but could be a nuisance during storage and also not
aesthetically appealing. Also, although it is an
easy and simple solution, there is always the possibility the power cord could
be accidentally tripped during operation and the live connections pulled loose.
Searching for a Connection
To make
the setup truly clean and tidy, the power connector and a switch needs to be
installed flush with the back panel like the original. However, there just isn’t
much room behind the RQ-85B PSU for a C14-inlet (like
that in the original PSU) let alone adding a power switch. Then it occurred
to me the smaller C6-inlet on my laptop’s power brick could be just the
right ticket.
This is the
power cable of my laptop with a C5-plug and the back of the Apple IIe platinum.
According to the IEC60320 standard, the C5-plug/C6-inlet combination is rated at 2.5A, and thus over
250W in North America. So it is more than sufficient for our purpose.
Finding the Right Parts
There are various C6-inlets (commonly known as the “Mickey Mouse” connectors because of their shape) on the market and this particular rear-side screw-on panel-mount C6-inlet (sometimes referred to as Schurter 0724) with solder terminals for wires fits my purpose well. Because of its slim housing, plan was made to install it in one of the connector openings at the back of the IIe.
This
C6-inlet in its original form will only fit into the largest opening (labelled 12) on the platinum
IIe. However, after removing some of the housing material from three sides (one aligned and two angled cuts as shown in the above picture) it will also fit nicely into one of the smallest openings (labelled 5, 6, 8 and 9).
This is
the top and bottom of the C6-inlets after and before modifications. The C6-inlet
housing is made with a relatively stiff black thermoplastic. You have
to be careful here particularly with machine tools because removing too much
material will either damage the C6-inlet’s housing or make it a poor fit which means
being easily pulled loose by the power cable.
The above is the KCD1-102 19 x 13mm boat rocker single-pole switch I sauced.
There are many makes and they are in general rated at over 1000 Watts and 100,000 mechanical cycles. I believe a double-pole version with the same dimensions (KCD1-104) was actually used by Astec and Dyna Comp in their IIgs PSUs (Apple model no. 699-0126). Initially I planned to use the
double-pole version (which is safer) but
later changed to the single-pole version for specific reason.
The KCD1-102
switch in its original form is a tad too big to fit into any of the connector opening except the largest (i.e. 12) on
the back of the IIe but I wanted to install it into one of openings 5, 6, 8 or 9 next to the C6-inlet. Fortunately,
this could be rectified by removing the right amount of material from its
four corners (four angled
cuts as shown in the above picture). The KCD1-102 switch housing was
made with a softer black thermoplastic so a hobby knife will suffice here. This was
where, from my experience, the double-pole version fell short because its housing
was thinner (due to the bigger switch
mechanism and illumination, if any, inside) and thus readily damaged before enough material was
removed. Note that the switch I used here was not the illuminated version so one of the solder terminals was removed since it was
not electrically connected and only there for mounting.
You may also want to install an electromagnetic interference (EMI) filter, in this case a ferrite bead (or ring, like that inside the original PSU, which was missing in my last project), to
comply with local electromagnetic compatibility regulations; and even a fuse or
circuit breaker in case you don’t trust the RQ-85B PSU’s own short circuit/overload/over
voltage protection circuit.
I had
two 12V 40mm x 40mm x 15mm fans handy so I tied them and two fan grills together
with cable ties for cooling the PSU. The dimensions of the two together match
that of the PSU cutout at the back of the IIe very well.
Piecing Them Together
In the first of the two platinum IIes, the CGA video and mouse connectors
have occupied openings 8 and 9, so the KCD1-switch and C6-inlet will have to be
installed in openings 5 and 6 (farther
away from the PSU). Before installing, check again no metal part inside the C6-inlet’s housing is exposed because of our modifications as you won't want any to touch the IIe's metal back panel. Unfortunately, the mounting holes of the C6-inlet does not match those of the smallest connector openings (i.e. 5, 6, 8 and 9; for DE-9 connectors) so I used plenty of hot glue to keep the C6-inlet in
place. Alternatively, you could drill two holes on the IIe’s back and mount
the C6-inlet with screws (or the other way round but I found drilling the C6-inlet somewhat difficult because of the holes’ positions in relation to the layout of the C6-inlet).
A larger heat-shrink was used to cover the entire back-end of the C6-inlet
as a secondary safety measure against exposed metal parts inside. Two cable
ties was tighten back-to-back around where the notches were on the C6-inlet and
acted as a restrain to prevent it from being pulled loose by the power cable.
The KCD1-switch was then installed in opening 5 and secured
with hot glue. The wirings were connected to the switch with crimp-spade
connectors (6.3mm female) and jackets for it made uninstalling the switch easier than with soldering. A single-pole switch should always be installed on the Live (NOT Neutral) power wire because it is the one
that carries dangerous voltage. The Neutral power wire normally carries current back
to the source and is usually connected to ground (Earth) at the main electrical panel or meter for simple household installations.
Nevertheless, it could at times also carry significant voltage since “real world” circuits are never perfect.
The AC power wirings were then wrapped around the ferrite bead as
close to the C6-inlet and KCD1-switch as possible to minimize EMI crosstalk due
to extended length of wirings inside the IIe case.
Heat shrink was used to cover the ferrite bead to prevent
damage to the wirings due to abrasion with installed peripheral cards. The
KCD1-switch was also covered to avoid any exposed dangerous voltage or the connectors loosening.
Notice
that connector openings 5 and 6 are directly behind slot 4. So this renders the
slot not available for most peripheral cards except may be a few with very short back-end (e.g. Uthernet I & II, some smaller Apple II Raspberry Pi adapters,
or some kind of flexible slot extension, etc.)
I
successfully reinstalled all the peripheral cards but found the cablings and
AC power wirings at the back a bit crowded mainly because of the ferrite bead. If you have, in the lower-number slots,
peripheral card with long back-end or connector(s) on the back-edge, you may want to try a different wiring
strategy here given the roomy interior of the IIe.
Case Solved
As a final check, I deliberately pulled the power cord out forcefully and the C5/C6 connection detached instantly without problem. So I deemed this setup safe enough for my ordinary use.
Following is the cost estimate of the parts used. For most electronic hobbyists, many of the parts may be readily available on their shelves and this would make a fun afternoon project.
Parts
|
Qty
|
Est. Cost (USD)
|
|
1.
|
Fan & Grill
|
2
|
8
|
2.
|
C6-Inlet
|
1
|
2
|
3.
|
KCD1-102 Switch
|
1
|
1
|
4.
|
Ferrite Bead
|
1
|
0.5
|
5.
|
AWG-18 Silicone Wires (ft)
|
10
|
6
|
6.
|
Heat Shrinks (ft)
|
1
|
0.5
|
TOTAL
|
18
|
Still living the Apple II dream!
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