battery eliminator for the UltraLite

Brian Smithson (
Sat, 23 Nov 91 00:55:45 PST

Warning: what follows is not for the faint of heart.

Are you tired of running down your UltraLite batteries at work?
Hate dragging that bulky charger around with you? In other words,
wouldn't you love to have an inexpensive AC adaptor that you could
leave at the office (or wherever)?

If you're reasonably confident working on compact electronics and
are willing to risk frying your favorite notebook computer, then
this may do the trick for you. To start off, I should give credit
to Robert Harker, esteemed UltraLite owner and list subscriber,
for suggesting that "the battery could be replaced by a block of
wood with a pair of contacts leading to a 12.6V DC supply, yes"?
Being somewhat more talented with a soldering iron than woodworking
tools, I took a different approach based on the same notion.

Before going on, I'd better cover my rear with the following disclaimers:

If you try this, you're at your own risk. It could fry. It could smoke.
It could burst into flames. Valuable data could be lost. Your family
and friends might laugh behind your back. It would be your own fault,
and I won't share in the blame. OK, here goes.

Parts needed:

(1) One 12V DC power supply. Get a good one, not one of those Radio
Shack things. You should get good regulation (+/- 5% or so) and
not a lot of ripple. I bought a Radio Shack thing and it put out
close to 15V and had about 100mV of ripple. Probably spiked out
when powered up too. It's in the garage now, and I'm now using
a nice little Lamda switcher, 12V @ 1.3A in a 3-1/2" X 3-1/2" X 1-1/2"
package, $15.00 at a surplus house. You'll also need other stuff
depending on what kind of power supply you get, like maybe a line
cord or fuse or metal case or whatever.

(2) About 6" each of three colors of wire, preferably stranded (for
flexibility -- this is the voice of experience speaking :-), about
24 gauge I guess.

(3) Some kind of plug and recepticle which disconnects a normally-closed
contact when the plug is inserted. I used a miniature phone plug
like the ones you see on Walkman headphones. The idea is that when
you plug in the battery eliminator, it disconnects the battery and
connects the AC power supply.

There are a couple of problems with mini phone plugs in this kind of
application: they expose their little voltages to the world when
unplugged, and they short out as you plug them in. For that reason,
I'm inclined to sequence things as follows: (a) plug in the plug,
(b) turn on the AC supply, and then (c) turn on the UltraLite.
You might want to consider using another kind of connector, like
for example the ones more commonly used for AC adaptors. I just
didn't happen to have one handy.

Tools needed:

Small philips screwdriver, soldering pen (low wattage please), needle nosed
pliers, wire strippers, a wee bit of insulating tape or shrinkwrap
for one of the connections and a drill (power or manual, your choice) for
drilling a hole to mount the AC adaptor recepticle.

Test equipment:

At least a volt/ohmmeter for testing. If you're unsure about the quality
of the power supply you get, then hook it up to an oscilloscope to check
for ripple and submit it to different loads to see if it spikes or does
anything weird.

Anti-static stuff:

The NEC service manual also says that the UltraLite should be sitting on
an antistatic mat and that the technician should have a wrist strap
connected to that mat. I opted to put a bedsheet on the table in order
to keep from scratching things up, and then scooted around the carpet
in wool socks. Use your own judgement here.


You're going to trash your silicon hard disk, so make as many backups
as you need in order to feel comfortable. It's not a bad idea to have
a fully charged battery on hand too.

Surgical procedure:

Since most of you don't have the service manual, I'll outline the disassembly
steps. The manual helped, at least in terms of getting the order of operations

(1) Put the unit upside down. Remove the ROM board cover, the Silicon
hard disk cover, and (don't ask me why) the telephone jack covers if you
still have them. If you've never removed the Silicon hard disk cover,
it doesn't have a little latch like all of the others; just press with
your thumbs and slide it toward the edge of the unit like you're trying
to open a Chinese puzzle box.

(2) Remove the ROM board: gently slide it in the direction of the little
"handle". It should come loose pretty easily. NEC used nice connectors.

(3) Remove the Silicon hard disk. No handle on this one, so I gently pushed
against the chips, moving it toward the edge of the UltraLite. The manual
suggests holding the end of the board, but I didn't see how I could get
a grip on that. Anyhow, it comes out about a half inch, enough so that
the connector is loose, and then you have to lift it out. Look at the
little tabs in the metal frame around the board, and match them up with
the cutouts in the edge of the board. You'll figure it out...

(4) Remove the Molicel battery. If you're like me, you did this already.

(5) Remove the backup battery cover. Gently remove the backup battery
connector that is visible from the hole where the ROM board was.
Snake that wire out as you remove the backup battery itself.

(6) Remove the eight black screws, four at the front edge and four at
the back edge.

(7) Hold everything together, and flip the unit over onto its bottom.

(8) Partially open the LCD panel. Remove the RAM/ROMcard cover and
any card that you happen to find in there.

(9) Gently lift the plastic which surrounds the keyboard and speaker,
from the front edge. It should kind of hinge up at the back edge
under the LCD panel.

(10) Remove the silver screw that goes through the circuit board which
extends from the right rear of the keyboard. Under that circuit
board is a green wire connected to the motherboard; disconnect
it. Now you can lift the keyboard out.

(11) Stand back and admire how much crap they packed into this little
unit. I really got a better appreciation for notebook computer
design after doing this, and haven't had so much fun since I replaced
a clock battery in a GRiD Compass II.

(12) Slide the white LCD ribbon cable lock to the left, thus releasing
the ribbon cable. Disconnect that cable.

(13) Skip this unlucky step.

(14) Disconnect the red wires coming down from the LCD panel into the
LCD power supply area. Make sure that they're free to move when
you lift the LCD panel out.

(15) Disconnect the contrast control wires at the right rear corner
of the motherboard.

(16) But wait, there's more. Remove the two screws and the little plate
in between them which holds the ground sheet in the center rear of
the base unit. Carefully remove the ground sheet. It may be a bit
adhesive, so kind of peel it off.

(17) Viola, you can now lift the LCD panel and keyboard cover off as a unit.
Spend a little time wondering if you really want to go on.

A little interlude to discuss the placement of the battery eliminator

I looked and looked for a good place to put a mini-phone jack. Surely
there was some room along the back panel where all of those other
recepticles were, or maybe there was some room on one of the sides.
Frankly, I couldn't find any places except two:

(a) There's room in the RAM/ROMcard slot cover just to the rear of
where the card goes. However, you'd have to carve out a bit
of plastic which adds some strength to the cover. You'd also
need to leave enough excess wire so that you could remove the
cover when you wanted to change cards.

(b) There's a wee bit of space on the edge of the keyboard cover
just above the "LOW BATT" legend. It's on the edge which
angles up 45 degrees or so. It's more or less in the same
place on the left side as where they put the contrast control
on the right side. It's a tight space behind, and so you need
to make sure that whatever jack you use doesn't take up much
space behind the panel. It's also a tight space in front,
because that edge fits fairly tightly when the LCD cover is
closed. There is enough room for a mini-phone jack as long
as the retaining nut was all that protruded from the front.
This is the location I chose.

Look around, though. You might find another place. When it really
gets worrisome is when you get out the drill and aim it menacingly
at the UltraLite.

OK, back to the surgery:

(18) Assuming that you chose the same kind of plug and jack as I did
and placed it in the same place, drill the appropriate sized hole
and make sure it will all fit.

(19) Connect your three wires to the jack. One will connect to the
long part of the plug (I'll call it "blue"), one will connect to
the tip of the plug (I'll call it "yellow"), and one will connect to
the contact on the jack which normally connects to "yellow" but which
disconnects when the plug is inserted (I'll call this one "green").
(20) I twisted the three wires together because it looks nice and helps
reduce EMI.

(21) Mount the jack in the hole. Bear in mind that the coating on the
inside of the UltraLite case is somewhat conductive. I checked
everything repeatedly with an ohmmeter, before installing the jack,
after installing the jack, and then once more just to be sure.

(22) Disconnect both the red and black wires from the battery terminals.
I think that the connector that those wires go into can be removed,
but I didn't bother. Remember which one connected to which terminal!

(23) Connect your yellow wire to the UltraLite red wire. Insulate the
connection. Make sure that it's reasonably compact -- this stuff
all has to fit together again.

(24) Connect both your blue wire and the UltraLite black wire onto the
battery terminal which had the black wire before.

(25) Connect your green wire to the battery terminal which had the red
wire before.

(26) Route the three wires along the front edge of the battery frame
(close in, because the keyboard fits there and doesn't leave much room)
and then up over that little transformer on the left, and then up
to the jack.

(27) Whew. It's worth doing one more ohmmeter check, and you can even
put the battery in and make sure that the correct polarities appear
at the jack using a voltmeter. Don't turn the unit on, of course.

(28) Time to reassemble everything. Put the ground sheet back on with
its clamp and two screws. Reconnect the contrast control and the
red power connector for the LCD panel. Slip the LCD ribbon cable
back into its connector and slide the white cable lock to the right
to lock it in place.

(29) Now is a good time to do a quick mechanical check. Put the LCD panel
and keyboard cover in place as though you were going to reassemble
the unit without the keyboard. You should be able to fit it snugly
without too much effort. If it won't fit snugly (check the seams
along the back edge and left side), then the newly installed jack
is protruding too much in the rear. If it fits OK, then slowly close
the LCD cover to make sure that it closes snugly as well. If it doesn't,
then the jack is protruding too much in the front.

(30) Lift the keyboard cover up again, and install the keyboard. I found
it easiest to hold the keyboard almost in place while I connected the
green connector, then move the keyboard into place. Don't forget the
screw in the right rear of the keyboard assembly.

(31) Carefully close the LCD cover and once again check to make sure
that it all fits nicely -- the seams should be tight and even all
the way around. Holding it all together, flip the unit over.

(32) Replace the eight black screws. Snake the backup battery wire
through the hole again, place the battery in its bay, reconnect
the battery wire, and put its plastic cover back on. Replace the
silicon hard disk board (remember those tabs and cutouts) and its
cover. Replace the ROM board and its cover. Replace the Molicel
battery. What the heck, put the RAM/ROMcard cover back on too.

(33) A moment of silence please. Promise to go to church from now on.
Think good thoughts about the electron gods. Do whatever you need
to in this momentous moment.

(34) Flip the unit over and turn it on.

(35) I'll just assume that it works fine. Turn it off, remove the
Molicel battery, connect your AC supply, power up the supply,
and then turn on the UltraLite again.

(36) If you're still reading this, then there probably wasn't an
explosion and fire. Congrats, you now have an AC adaptor for
much less than the $150 or whatever that NEC wants for a charger.

You have to reinitialize the disk. If you changed the cluster size
using Norton Utilities or something like that, you'll need to do that
again too. Then you can restore your backups.

-Brian Smithson
 Motorola Inc., Computer Group, Commercial Systems Division
 10700 N. De Anza Boulevard, Cupertino, CA 95014 USA, (408)366-4104, {apple | pyramid}!motcsd!brian