Resources
Wiki
oldcomputers.net – setup disks
Documents:
Product Bulletin
Motherboard jumpers
Service Manual
Internals
Motherboard
The computer will not access HDD when the CMOS battery is discharged or absent. There are two versions of the batteries possible:
- Integrated inside Dallas DS1287 real time clock controller chip. It is easy to replace the integrated battery with an external one, following these instructions. Please mind that my computer is missing the back cover, so maybe the battery needs to be positioned differently, but the idea is basically the same.
- Separately soldered to the board, with MC146818 chip instead of DS1287 – this version will have additional resistors, diodes and oscillator soldered near the chip and the battery. These components are missing in the Dallas version where some zero-ohm links are soldered instead.
Video Board
Floppy Disk Drive
Hard Disk Drive
Power Supply
Display
Panasonic MD400F640PD5 – gas plasma display.
Keyboard
This is not the original keyboard coming with Portable III, but one taken from Compaq Portable 386. The keyboard seems to be compatible, also physically fits the cover perfectly.
Compaq Portable keyboards had cords in which the plastic cable coating broke easily with time and fell off leaving the bare cables visible. A vintage keyboard extender may be used as a replacement.
Reassembly
Other
Signal at pin 2 of the LCD screen 4-pin power connector
Hi, you can tell me the pinout scheme voltage of the 4-pin red molex connector that powers the LCD screen. Then the voltage is in DC or AC? please.
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Yes I will take a look during the weekend as I am away from it now.
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Thanks. The purpose is to replace the original power supply with a modified atx pc or a modular power supply.
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Do you mean this connector: https://oldcraporg.files.wordpress.com/2018/11/dsc_0071-1.jpeg
It is not red in my machine, but this is the only one with four pins.
The voltages are:
pin 1: ground
pin 2: +5V (not clean signal, see the picture I added at the end of this post)
pin 3: -200V DC
pin 4: -200V DC
pin 3 and pin 4 are not the same, the resistance between them towards the motherboard is 600 ohm
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thanks for your help. That white connector then connects to the red molex connector of the main power supply. Are the 200 dc volts negative?
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Yes negative against pin 1
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it will be difficult to find a power supply that does even -200volt dc together with +5 +12 -12.
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Love the machine and this is some excellent documentation! I have a Portable III myself, and am in the middle of replacing the old frayed keyboard with a new cable. I made the mistake though of not documenting the pinout of the old cable, and every combination of wiring I can think to try from the new cable to the keyboard’s internal connector doesn’t seem to work when testing on the machine. Do you happen to know the pinout between the keyboard port on the machine to the keyboard’s internal connector? Thanks in advance!
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I am sorry I missed your comment. I have not made any notes of how to connect the keyboard. Did you manage to solve it? I might open the keyboard and see, this should be easy.
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The display is gas-plasma technology, not LCD, that’s why it needs the -200V.
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Thank you, I fixed the description.
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