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Toshiba T3200SXC fix/upgrade: new PSU, LCD, WiFi

Restoration of 31-year old first* portable with color TFT screen. Re-designed PSU, adaptor for new LCD, WiFi with untouched chassis

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In this project a huge and heavy piece of old portable PC technology with 16MHz Intel 386SX CPU was brought back to life. The repair involved re-designing and re-creating the internal power supply (the original one was eaten by the corrosion from leaked capacitors), adapting a replacement screen to be used with this machine (that involved making 9-bit to 18-bit TTL RGB adapter and 3D-printing mechanical adapters).

Re-designed PSU was a DC-DC one (the original had AC input and no battery), so the machine was enhanced with the functionality of being battery-powered with USB-C PD powerbank.

Another enhancement was the addition of wireless connectivity, with easy-to-use interface that allowed scanning networks and connecting to them from MS-DOS 6.22, thanks to the integration with small OpenWRT-enabled module.

Further enhancement was the addition of internal speakers and ISA sound card, which allowed this machine to become a fully-fledged multimedia retro-gaming portable PC.

* First portable computer with TFT/color active matrix screen according to Z*NET International Atari Online Magazine (#91-13, vol. 7, no. 13, April 5, 1991) and Toshiba TEG October 2002, Art. No. CBB2B 10/02E, pp. 4.

Introduction

I made a quick overview of the work that has been done in this videos (I plan to prepare more videos on the details):

Toshiba T3200SXC is probably the first (1991) portable computer with a "modern" color LCD screen, a TFT one. Therefore it is a significant piece of computer history. It also has ISA expansion slots, which give  some  endless opportunities for the expandability. Unfortunately, this unit had faulty screen and power supply. I described the original state of the machine in this project log post.

The challenge

The goal of this project is to repair this machine and make necessary enhancements (albeit possibly non-destructive ones) to keep it usable in 2022 and forseeable future. That does not mean turning it into a viable daily-driver PC, but rather restoring its original functionality and enhancing user-frendliness, so it can serve as a functional, portable, all-in-one and fun-to-use example of early 90s digital culture heritage.

What to do

With that being said, the restoration/repair objectives are:

  • Create a replacement for the broken power supply [working prototype has already been made]
  • Replace the broken LCD screen with one that would be indistinguishable from the outside, and would have the same resolution [a prototype of necessary converter and 3D-printable mount adapters were already made]

Because the prototypes have already been made with basic home fabrication methods, the additional goal is to tidy-up the design files, fix possible issues and publish them so they can be used with other machines, or even adapted to other types of machines.

The enhancement objectives are:

  • Allow the computer to be battery operated [done by a USB-C PD to DC jack adapter]
  • Add internal speakers and sound card [done with ISA expansion card and speakers recycled from another laptop]
  • Add easy-to-use wireless network connectivity, to make file transfer and accessing web easier [prototype stage, using embedded OpenWRT router, automation scripts and ISA Ethernet card]

Constraints:

  • keep the external form of the computer intact
  • enhancements have to be stealth and must not interfere with the "retro look and feel" of the machine
  • no modifications to the motherboard itself, only peripherals can be modified

Such constraints were chosen in order to prevent the machine from being enhanced "too much", that means no 4K screens or gutting the internals and completely replacing them with something else.


Fun part:

  • try to check what is possible witch such an old machine, obviously besides playing retro games [in progress].

Some historical facts

The active-matrix color screen used in this machine was a big deal, because it had quick response times and wide viewing angles. Passive screens (DSTN), which were popular even up to late 90s, had massive ghosting issues (it could take few seconds to completely refresh the screen, and mouse cursor /if mouse was being used at all/, could be virtually invisible during motion) and were just generally bad (but much cheaper than TFT). The cost of Toshiba T3200SXC was a whopping $7,249 in 1991, and that's just for the base model with 1MB of RAM (PC Magazine June 25, 1991, pp. 44). Here we have 7MB!

It was also featured in Microsoft Excel 1992 video:

Funnily enough, this computer was never capable of being battery-operated, yet it was shown as such in this promotional video. I wonder if the film crew has also been using USB-C powerbank to power it on!

Project takeaways and further perspectives

Even though Toshiba T3200SXC is a rather rare machine, the accomplishments of this project should be adaptable in some way to other PC-type machines.

  • Re-designed PSU has +5V, +12V, -5V, -12V power rails with an extra +12V2 rail for the LCD, which...
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dcmount_ver23jul2022.stl

3D-printable DC jack mount adapter

Standard Tesselated Geometry - 63.46 kB - 07/23/2022 at 23:03

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t3200sxc_lcd_adapters_ver22jul2022.stl

Files for 3D printing the LCD mounting adapter

Standard Tesselated Geometry - 86.12 kB - 07/22/2022 at 17:49

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t3200sxc-grb-ver22jul2022.zip

Gerber files for the LCD adapter (version 22 july 2022) (not manufactured yet)

x-zip-compressed - 39.94 kB - 07/22/2022 at 17:35

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t3200sxc-new-psu-grb_ver22jul2022.zip

Gerber files for the new power supply (version 22 july 2022) Applied some modifications after the prototyping stage - updated clearances, converted to double sided

x-zip-compressed - 112.88 kB - 07/22/2022 at 17:33

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  • 1 × LQ104V1DW01 Replacement LCD (18-bit TTL RGB interface)
  • 1 × D36V50F5 5V, 5.5A Step-Down Voltage Regulator
  • 2 × D24V22F12 2.2A Step-Down Voltage Regulator
  • 1 × PDC005 15V/20V USB-C PD trigger
  • 1 × A5-V11 RT5350F mini router with OpenWRT

View all 6 components

  • Ideas on how to use it

    Wojciech "Adalbert" J.07/23/2022 at 23:30 0 comments

    I'm trying to research some potential cool uses for this machine. Will try to look for more and evaluate them in practice.

  • Installing speakers and a sound card

    Wojciech "Adalbert" J.07/23/2022 at 23:28 0 comments

    I managed to fit small stereo laptop speakers in the case. I just soldered some wires directly to the sound card (but I included a connector on the cable, so the speakers can be easily unconnected if needed).

  • Getting it on wireless network

    Wojciech "Adalbert" J.07/23/2022 at 22:30 0 comments

    It turns out that this 16MHz machine is quite capable, as I managed to connect it to wireless internet and post a comment on this very page:

    I used a tiny A5-V11 router with RT5350F SoC: https://openwrt.org/toh/unbranded/a5-v11 that I flashed with OpenWRT. Currently I am connecting it externally to the ISA ethernet card attached to T3200SXC, however I plan to embed this tiny OpenWRT module directly onto the ISA card. This is how it would look like piggybacked:

    It uses just around 1-2 watts of power, so I plan to find a suitable soldering point with +5V on the wireless card and solder wires in series with a small polymer fuse. The ethernet wires will need to be soldered between these two cards - i may desolder the RJ45 connectors completely. To avoid blocking the wireless signal, metal bracked will need to be replaced with a 3D-printed one.

    On the software side, I prepared some scripts for both the MS-DOS machine and OpenWRT router, that allow for very simple scanning and connecting to the networks directly from MS-DOS. Details will be stored in this repository: https://github.com/adbrt/dos-wifi-solutions/

    For a web browser, I'm using Links for DOS: http://links.twibright.com/download.php

    It supports TLS 1.2 and it even has a graphical mode! However it slows things down quite a bit:

    I also managed to connect to a Wi-Fi control interface of a digital camera (Lumix GH5). The camera detected that the connection has been estabilished. I wonder if I could take some photos, download them to the DOS machine and upload them online using HTTP interface of the camera. I will need to look into the protocol and try some things out. You can see here how the wifi scan / connect command works:

    By the way, as a bonus, I will mention that old-school ISA 2.4GHz wireless networks adapters did exist, and in fact here is one that I tried to use with that computer!

    However it is completely incompatible with modern Wi-Fi protocol - so it wouldn't be much of an use. Therefore I'm going with the embedded OpenWRT module option.

  • Replacement power supply

    Wojciech "Adalbert" J.07/22/2022 at 14:55 0 comments

    Old (top) and new, smaller power supply (bottom)
    Old (top) and new, smaller power supply (bottom)

    A prototype power supply was fabricated using mostly readily-available DC-DC modules and home-etched PCB made by exposing a board coated with UV-soldermask under a 3D-printed mask.

    The power supply required following rails:

    • +12V for mainboard/HDD
    • +12V for LCD with turn on/off signal
    • +5V
    • -5V
    • -12V
    Schematic
    Schematic of the new power supply

    Preparing PCB for etching by spreading UV-curable soldermask and exposing it under 3D-printed mask

    Preparing PCB for etching by spreading UV-curable soldermask and exposing it under 3D-printed mask
    New power supply
    New power supply

    I described the process of creating a PCB for this power supply in this project: https://hackaday.io/project/186467-making-pcbs-with-3d-printed-stencil-and-uv-paint

    and in this video:



    Major components of the power supply:

    • D24V22F12 12V 2.2A step down converter x2
    • D36V50F5 5V, 5.5A Step-Down converter
    • LC-MC34063A-NV negative voltage converter module
    • LM7905 -5V negative voltage stabilizer
    • 5V and 12V SMC and SMB TVS diodes for rudimentary overvoltage protection
    • 5A polyfuse
    • 250mA polyfuse
    • low ESR capacitors, ceramic capacitors

    The power supply will be able to operate on wide input voltage range (ca. 15-24V), as all of the voltage rails are generated using step-down converters. It could be more cost effective to use just 5V and -5V, -12V converters, and use +12V directly from the DC input, but that would require some additional, active overvoltage protection, as it would be much easier to mismatch the power supply. It would be also possible to use just one +12V converter if a mosfet would be used to power the LCD on/off, but two converters were used to spread the load. ENABLE pins of +12V and +5V converters were used to provide soft power on-off functionality and to allow switching the LCD on and off (with help of additional transistor).

  • Replacement LCD and signal adaptor

    Wojciech "Adalbert" J.07/22/2022 at 14:01 0 comments

    I wanted to connect replacement LCD to the original LCD connector, with no "ugly hacks" like interfacing with VGA connector and other workarounds. The original LCD used 9-bit TTL RGB interface (3 pins for red, 3 pins for green, 3 pins for red), which understandably is quite dated, especially considering the fact that this was probably the first laptop with color TFT screen.

    I was able to only source replacement screens with 18-bit RGB interface (i chose Sharp LQ104V1DW01), with much slimmer outer casing (but the same screen area and resolution). Therefore I needed to adapt new screen both electrically and mechanically.

    The original interface had 8 possible values for each color (0,1,2,3,4,5,6,7, or 000 to 111).

    On new LCD, there are 64 possible values for each color (0 to 63 or 000000 to 111111).

    The idea was just to ommit half of the R, G, B pins. The lower pins (RGB0,1,2) on new LCD would remain unconnected. The upper pins (RGB3,4,5) would be connected with RGB0,1,2 from the computer. Now the maximum value for each color will be 111000, which is 56 out of 63. That limits the maximum brightness of the screen to 89%, but this should not be a big deal.

    Schematic of the LCD adaptor
    Schematic of the LCD adaptor

    There are also UD (up-down), RL (left-right) pins on the new LCD, which can be pulled either to ground or VCC. They can be used to rotate or mirror the image. I left them floating, however a option of jumpering them remains if ever needed.

    A prototype was produced using a single-sided home-etched (laser toner transfer) PCB, with 2.0mm 28pin header and directly soldered 0.5mm 32-pin ribbon. Because the board was single sided, it required a bit of jumper wires. The screen did work and I partially potted the PCB in epoxy.

    Prototype of LCD adapter. Two additional wires were routed only because I damaged two pads on the adapter.
    Prototype of LCD adapter. Two additional wires were routed only because I damaged two pads on the adapter.

    The backlight inverter also needed to be hacked, as I didn't have a matching one for the new screen, and I couldn't use the old one. There was no brightness level signal on the T3200SXC, so I had to connect EN pin with ADJ pin. That way the backlight was on as soon as +12V was provided to the board.

    This is how a more production-ready board would look like, with a double sided PCB, pads for FPC connector and some mounting holes:

    Updated version of LCD adapter
    Updated version of LCD adapter

  • The original state: what was broken?

    Wojciech "Adalbert" J.07/21/2022 at 22:33 0 comments

    When I acquired the machine, the original power supply was still working, but the screen, the miracle of 1990 technology, active color matrix 640x480 Sharp LQ10D013 unfortunately was severly degraded. The image was almost entirely (FFFFFF-like) white, with some barely visible pale (FEFEFE-like) characters. After some time the screen got completely dead.

    LQ10D013 LCD in case
    LQ10D013 LCD in case


    I decided to replace it with another TFT screen with 640x480 resolution, also made by Sharp: LQ104V1DW01. It was a newer model, much slimmer but same screen size, also backlit by CCFLs, also utilizing TTL RGB interface but with 18-bits instead of 9-bits (it was much easier to find an 18-bit replacement, as this is a more modern standard). Therefore it required to be adapted mechanically and electrically, and that process will be described in other updates.

    Old and new LCD
    Old and new LCD

    After some time the power supply also died and the machine was no longer turning on. Getting to the PSU was much more difficult, as it required tearing down the entire machine. It turned out, that there was a massive capacitor leak and the board was covered in electrolyte, showing signs of corroson.

    Damaged power supply, visible leak
    Damaged power supply, visible leak
    Old power supply, top side
    Old power supply, top side

    It might be possible to clean up the PCB, restore any damaged traces and replace defective components, however I would like to avoid working with high voltage AC. The power supply technology has also advanced quite a bit over the years, so I decided to rebuild the PSU from scratch, using DC-DC converters, thus enabling battery opperation and even powering from USB-C PD powerbanks.

View all 6 project logs

  • 1
    Replacement power supply

    The power supply can be built using project files and gerber files attached in file list of this project.

    BOM (a list with product names will be prepared too)

    • Cables desoldered from original power supply
    • D36V50F5 DC-DC converter
    • 2x D24V22F12 DC-DC converter
    • LC-MC34063A-NV negative voltage converter module
    • L7905 TO-220 negative -5V voltage stabilizer
    • 680uF/35V low ESR capacitor (note: capacitor values are not necessairly critical, and are probably overspecced a bit)
    • 2x 330uF/25V low ESR capacitor
    • 1200uF/10V low ESR capacitor
    • 2x 820uF/25V low ESR capacitor
    • 1x 390uF/10V low ESR capacitors
    • 1x 10uF/25V electrolytic capacitor
    • 3x 10uF/25V 1206 SMD capacitors
    • 7x 1uF/50V 1206 SMD capacitors
    • 33V TVS SMC unidirectional
    • 12V TVS SMC unidirectional
    • 12V TVS SMB unidirectional
    • 5V TVS SMC unidirectional
    • 5V TVS SMB unidirectional
    • 2x 2k2 1206 SMD resistor
    • 22k 1206 SMD resistor
    • 150R 1206 SMD resistor
    • 2k7 1206 SMD resistor
    • SOD-123 Schottky diode
    • 3x BAT85 Schottky diode
    • BC818 SOT-23 transistor
    • 5A polymer fuse (THT)
    • 250mA polymer fuse (THT)
    • 5.5/2.5 DC barrel jack
    • 2.54mm 2-pin fan header
    • Power switch
  • 2
    LCD adapter board

    The LCD adapter board can be built using project files and gerber files attached in file list of this project.

    BOM:

    • 2x18pin 2.0mm pitch angled pin header
    • 32pin 0.5mm FPC connector (Hirose_FH12-32S-0.5SH_1x32-1MP_P0.50mm)
    • Optional 1206 1k SMD resistors used as jumpers for left/right or up/down image rotation/mirroring
  • 3
    3D-printable adapters

    3D printable adapters for LCD mount and the barrel jack DC connector can be printed using STL files attached in project repository.

View all 3 instructions

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Wojciech "Adalbert" J. wrote 07/23/2022 at 21:48 point
I'm about to post a comment directly from this 1991 machine, connected via wireless network, using a Links browser in MS-DOS 6.22. If you can see it here, it means that it worked!

  Are you sure? yes | no

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