MiniSport Laptop Hacker 14

eZine lover (@eZine)

Published in 

MiniSport Laptop Hacker

 · 5 years ago

  

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