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