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