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MiniSport Laptop Hacker - Vol #22. July 1994
To discourage pecuniary interests, Copyright (c) 1994 Brian Mork
>>> ADMIN
The MLHacker series is formatted to print out on 8.5"x11" sheets manual-
ly fed into an Epson LQ-850. I print at 8 lpi, which gives 82 lines per
page. Back issues are available from ftp.cs.buffalo.edu in the
\pub\msdos\ham-radio directory. E-mail server ham-server@grafex.cuper-
tino.ca.us also has them in the directory \hamradio\newsletters. Note
in the signature block that my packet radio address has changed.
>>> ALTERNATE BATTERY SOURCE
In April Jim forwarded me results of his efforts to modify 9.6 volt
Makita power tool batteries. Cut directly from his Internet message,
here are his observations (thanks Jim!):
"Just the other day I did something I've been dreading for 6
months. I removed the stock battery from my Zenith ZL-2 Minis
port and connected a variable voltage power supply directly to
the computer's power terminals. After adjusting the supply to
six volts, I powered up the computer and verified that it was
working properly. Then, taking a deep breath, I slowly cranked
the power up to ten volts. No explosions, no complaints from
the Minisport power supplies, It took it just fine. Great, now
I can use my 9.6 volt Makita batteries with the laptop as part
of my portable packet station.
"Since the internal Zenith supplies are all switchers, current
drain is inversely proportional to battery voltage. This means
no power is wasted regardless of whether the voltage is 6.0
(stock Minisport battery) or 9.6 volts (as in my Makita pack). I
measure 450 - 650 Ma drain with a 6.0 volt source (depending on
backlight brightness), but with a 9.6 volt source, only 340 -
425 Ma is needed. The Makita batteries are about 1400 MAh ca
pacity and run my ZL-2 for 3 hours with the backlight on full.
Obviously, a 7.2 volt external would work also, with proportion
ally reduced operating time.
"I had to make a better way to get the external power to the ma
chine than the alligator clips I was using. I thought I'd share
what I built with you all. Here's how to make a fake battery
pack for your Minisport.
"Begin by cutting a 2 1/4" by 5 1/8" piece of single sided glass
epoxy Printed Circuit board material. Remove 1/16" strips of
copper along five lines as shown in the following diagram.
|<-------- 2 1/4" ---------->|
>|---- 1 1/2" --->| |
>|- 1 1/16" -|< | |
>|- 3/4" |< | | |
5/16" | | | |
>| |< | | | |
_______ _____________________________
^ | | o | | o | | < drill holes for
| | | + | | - | | power wires
| | | | | |
| |--|----|---|----|-----------| < remove copper
| | | | | | for 1/16"
| | | | | | |
| | | | | |
| | | | | | |
| | | | | |
| | | | | | |
| | | | | |
| | | | | | |
| | | | | |
| | | | | | |
| | | | | |
5 1/8" | | | | | |
| | | | | |
| | | | | | |
| | | | | |
| | | | | | |
| | | | | |
| | | | | | |
| | | | | |
| | | | | | |
__v___ |__|____|___|____|___________|
^ ^ ^ ^
Remove copper along these four lines
"Drill the two holes close to the edge so solder will not inter
fere with the power contacts on the machine. Only the two
small rectangular areas with holes will actually be energized.
Isolating these minimizes the possibility of short circuiting the
battery. Nevertheless, you should always disconnect the external
battery when the fake unit is removed from the computer.
"You can remove strips of copper by double scoring the material
1/16" apart along the indicated lines, then gouging out the met
al with a knife or wood chisel. With some patience, you can
also do it with a hacksaw or a hand grinder. My favorite method
is using a 1/8" drill bit in a small drill press as a router. I
raise the table until the PC board is just touching the drill
bit. Then one or two thickness of 3 x 5 card under the board
raises the copper just enough so I can route out metal along the
lines by moving the board under the bit while it's turning at the
highest speed. I have a piece of wood with a vertical fence
screwed to one edge that I can "C" clamp to the drill table to
help guide the PC board while routing.
"You will need to solder a power cable directly to the board, or
glue some sort of jack on the board to accept a power cable
through the battery cover hole. The NEGATIVE terminal is nearest
the front of the Laptop. The POSITIVE terminal is the rearmost.
You won't need a connection to the center terminal, it is used by
the Minisport charging circuit. Use a minimum amount of solder
and file the solder bumps down smooth.
"Complete the fake battery by gluing a block of wood about 1 inch
high to the glass side of the PC board. This takes up the slack
in the battery compartment so the board is pressed firmly onto
the computer's power terminals. You will have to sand the block
to just the right height, or glue on strips of cardboard for ex
tra height if it's too short.
"One problem with using a higher than six volt battery with the
Minisport is that the low battery voltage alarm doesn't work. It
appears that by the time the 9.6 volt pack is discharged far
enough to trip the alarm, it's going down so fast that there
isn't time for an indication. Save your work often if you're
near drop out time. It should be possible to construct a sepa
rate discharge alarm on the fake battery board that will trip at
a higher voltage and give a couple of minutes warning.
"I have also created a real battery pack for my Minisport by us
ing one of these routed out PC boards, and hot gluing five "C"
size nicads to the top. It works as well as the 1700 MAh Minis
port batteries but I have not figured out a way to use the Minis
port charger. Also the exposed battery power terminals on the
bottom require care to avoid short circuits.
>>> DRIVE EXPANSION PINOUT
On the back of the Minisport is a small plug with a rectangular external
form and an internal "D" shape. I have been unable to identify a source
for this connector, but several people have asked for the pinout. Here
it is, compliments of wa8wzx. The top row of pins 1 through 19 are all
sequential odd numbers. The bottom row has pins 2 through 20. Pins 4,
10, 12, 19 & 20 are all ground. Others are:
1 Disk Change 2 Side Select 3 Read Data
5 Write Protect 6 Track 0 7 Index
8 Write Enable 9 Write Data 11 Step
13 Direction Select 14 Drive Select 2
15 RPM 16 Motor On 17-18 Vcc
Please provide feedback! * Direct data 1-509-244-9260
* ARO Net KA9SNF@ka7fvv.#ewa.wa.usa
* Internet bmork@opus-ovh.spk.wa.us
73, Brian * 6006-B Eaker, Fairchild, WA 99011