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