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MiniSport Laptop Hacker - Vol 17, Nov 1993
Copyright (c) 1993 Brian Mork -- "not to make money, but to keep it that
way for others, too."
>>> ADMIN
Remember, you can get copies on disk of any software or text files (in-
cluding the MLHacker series) I refer to by sending me a disk and SASE.
I'll put a variety of other MLHacker related goodies on there, too.
Alternately, contact me using the information in the signature block.
Please, contribute!
MLHacker is available on the KA6ETB Internet HAM-Server. Send a message
to ham-server@grafex.cupertino.ca.us with the single line of text: HELP
to get access information. Check the \hamradio\newsletters directory.
I'm watching for other Packet or Internet archivers who will host the
MLHacker series.
>>> POWER SUPPLY
A lot of people have a problem where the computer fails to stay powered
on. Two LEDs blink for a second or two and then the computer powers
down. One of mine has been having this trouble, too, and I finally had a
chance to reverse engineer the power supply.
The Minisport power supply pinout to the motherboard is via a 16 pin mini
scotchflex connector. Pin 1 is indicated by a white arrow on the power
supply board. Reverse engineering was carried backward into the power
supply only until I was reasonably sure I understood how the circuit was
suppose to work. Notice some capacitors seem to be reverse biased. Sur-
face mount dielectric capacitors still have the banded end negative,
right?
Pins 2,5 and 6 are not accounted for yet because of unidentified compo-
nents. Pins 5,6, and 10 are the ones with bad voltages either causing my
problem or as a result of my problem. What a coincidence, eh? Here's
what I've been able to determine. I'm particularly interested in what
- your* header voltages are if you have this notorious power-off failure
mode. These schematics are not a "sure thing" -- they're determined us-
ing visual trace following, an ohmeter, and a diode checker. I'm partic-
ularly unsatisfied with the Pin 10 circuitry. Other fixit experts out
there, please give me ideas!
S487 1004 bobbin "-B"
.-->|-->|-.----.--~~~~-.----.----.-->|-.---.------ Pin4 (+5v)
( | | | | | | |
) P11 | | | \-\ | 100| LB|
( H922 | 470| 4.7| - ^6.8 | === ===
) xformer | === === |Znr | | |
( | | | + | | | |
| / / / | / /
| |
| .----->|---.----- Pin1 (+5v to only
.-- glass diode S487 | 2nd MB RAM)
to Pin10 ===
circuitry |LB
|
.----- Pin3 (GND)
|
/
A3 bobbin
.---------------------------->|---.---~~~---.----- Pin7 (+10v)
( | |
) G923 === ===
( P12 | |
) xformer / /
(
A3 bobbin
.------|<---.---~~~---.--------------------------- Pin8 (-10v)
( | + | |
) G923 === === ===
( P12 | 47 - | 3.3 LB |
) xformer / / /
(
.-- Pin11,13,14
|
| (GND)
/
608C04
.--. bobbin
| |----.-------~~~-------.----.---------------- Pin15,16 (+5v)
.--. | | |
.---. 100 | \-\
1000| | 0.1 === ^
=== === | |6.8v
| | | | Znr
.---. / /
| |
/ edge |14
MB3778 |----- Pin 9 (from computer)
| (_stby)|
MIDL -----------. center | |
| MB3778 |14
+5v(pin4) / 10k (_stby)|------------------ Pin 12 (from computer)
| \ |
| / |
1 / | 4.7K
0 \ | .-/\/\--.
0 / / variable | | "-B"
K \ --\--> resistor | -.--|<- Pin 10 (6.6v when working)
/ / | /
| | 10K | |< BV3
---->|----.----.------<\ /---/\/\-.---| PNP
glass | | \/ |\
diode | \ ---- |
from |LB /51K | CBZ2 |
Pin4 === \ | NPN +5v(pin4)
circuitry | / |
| | |
.----.--------.
|
/
MIDL is identified in MLH Vol 14 -- in essence, it is +9v power, deliv-
ered through a diode.
LP stands for "Little Beige capacitor." I'm guessing they're 0.01uf by-
pass capacitors. They have no markings.
In order to progress further, I need to know the identification of a few
parts: "24" - 3pin rectangular SMC, 1/16" x 1/8"
"14" - 3pin rectangular SMC, 1/16" x 1/8"
"BV3" - 3pin rectangular SMC, 1/16" x 1/8"
"CBZ2" - 4tab SMC, looks like fixed volt reg (3 + tab)
Please provide feedback: * BBS 1-509-244-9260
* AX.25 KA9SNF@wb7nnf.#spokn.wa.usa
73, Brian * Internet bmork@opus-ovh.spk.wa.us