MiniSport Laptop Hacker - Vol 14 25 May 1993 Copyright (c) 1993 Brian Mork >>> ADMIN Things have been pretty quiet this time around. I got only one message back from the field. In the meantime, I managed to bring up an Internet node in-house, and I'll start porting these newsletters over there, too. Look in the micro.zenith and rec.radio.amateur.packet forums. If you read these MiniSport Laptop Hacker newsletters, please make it a practice of kicking back at least a one line message indicating what parts are particularly useful or not useful. >>> POWER SUPPLY HARDWARE Well, for those of you that have been following the MLH series, you'll know that one of my power supplies has been giving trouble. It finally gave up the ghost. Simultaneously I heard from another ham who had near- ly identical symptoms: The Power & NumLock LEDs flash on for about 1/2 second and then the computer power downs by itself. From Internet, I heard from one person who bought his for a real price, with a guarantee. Its power supply died this way, also, and the seller replaced it. He's had no problems since. Too many similar stories! I wanted to know what's going on! In the meantime, I'm looking to buy broken MiniSports. I tore mine open and started from the exterior working in. There are a handful of components that condition power and select where power is com- ing from --the AC adapter or the battery. This initial power supply sec- tion is documented below. My two ZL-x computers are different: Older Newer --------------------------- ----------------------------- * Power supply piggyback * Power supply all on one card card with number PA2020P25 with number PA2020P65 * Motherboard 1PC1606AMB-40I * Motherboard 1PC1606AMB-41I, with green patch wire from no patchwire from/to Test TP43 Point 43. * U47 BIOS is "BIOS V3.3D" * U47 BIOS is "444-804" * Disk controller WD37C65BJM * Disk controller is same part has manufacture date in number dated 44nd week in 22nd week of 1989. 1989. The power conditioning sections are physically different, but electrical- ly they're the same. I expect my older one was a "fix-it" prototype that later made it onto the production board. Here's the schematic of the piggyback section: +------------->|-----+ | ........ D1 | | . . | | . \ . | +---~~~~----~~~~-----BJ ylw "BA"------+----+ \----------+ | | L1 L2 (battery) . . | | | . . | | | red "AD"------+------+---->|----+--+---+--------------------MIDL (9v pwr) | . _) . D2 | . (_ . D3 | . _) . ^ . (_ .K1 | . _) . | . (_ . | . ) . blk "G"-------+------+--------------------------------------GND (ground) ........ D1,D2 - two B8300s or integral N9K-60QC04 BJ named because the D3 - ceramic bubble (part no. unknown) older power supply has L1 - approx 24 turns on 1/4" form a Blue Jumper wire. L2 - 1 turn on core K1 - SPDT DIP relay, bottom M AD n/c MIDL named because it view * * * is the MIDDLE wire pinout: | connecting the piggy- * * * back board. GND BA Operating from battery power, power comes in through D1 and out both the BJ and MIDL connections. When the 9v is available, current comes in through D2, again going out BJ and MIDL. My suspicion is that one of these carries the main power current and one is a monitor tap, i.e., in- dicates when AC sourced power (9v) is available. Additionally, K1 pulls the contact closed, providing current back to the battery pack for charg- ing. If you listen carefully when 9v is connected, you can hear K1 click closed. the glass diode (D2) provides a shorted path for the current spike coming from K1 when it clicks off. Notice that this circuit is in operation whether or not the computer is turned "on." It might be more appropriate to think of the computer as always being on; when you press the on button, the power supply just "upgrades" to full output status. The rest of the power supply (all stuff between what I presented above and the header I described back in issue ????) lives on an approximately 5"x4" circuit board. Reverse engi- neering of this board has been slowed by my inability to identify three chips. There are two of each of the following: MB3778 (16-pin IC), K612 (3-terminal + heat sink tab), and D4049G (16-pin IC). PLEASE FORWARD ANY INFORMATION YOU HAVE ON THESE THREE CHIPS. 73, Brian, ka9snf@wb7nnf.#spokn.wa or Internet bmork@opus-ovh.spk.wa.us