Commodore C386SX-LT

Resources

Wiki – no wiki page exists for this machine
classicomputer.de

Please compare with Commodore C286-LT.

Internals

Motherboard

2MB Memory Module

Reverse-engineered schematic is available at my Github. This is a Mitsubishi MH1M16JS memory module.

LCD Screen

Sanyo LCM-5474

Backlight Power Inverter Module

Hard Drive

43MB Toshiba MK1122FC is HDD type 17 in BIOS.

Floppy Disk Drive

TEAC FD-335HF 063-U

LED Panel

Keyboard

BIOS

BIOS entry key combination is CTRL-ALT-ESC pressed after the system booted.

Power Supply

The original BIOS battery is AA-size 3.6V Lithium battery. It can be easily replaced with popular 1/2AA size 3.6V LiSOCl2 batteries.

The power supply is pretty unusual and hard to replace. The pinout is described on the picture below. My laptop had the capacitors on the power supply board leaked. This caused the voltage to the LCD screen go out of the original range and turning the contrast wheel to the maximum contrast level provided voltage that actually killed the portions of the LCD panel – hence the dark vertical line on it.

If there is no need to charge the battery, it is possible to connect only +12V voltage and ground pins, for example from a router power supply that was described on the Atari SF314 FDD page. The power plug is Mini DIN 6-pin and is generally available today to purchase.

Battery

My computer came with no battery. For information about battery and its replacements, please see post about Commodore C286-LT. It is exactly the same in both models.

Reassembly

19 thoughts on “Commodore C386SX-LT

  1. Hey Pawel, I just got my hands on the same machine. Mine is faulty, power supply sounds like it took a lighting hit. Do you have any schematics for it?

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  2. Are you able to draw pcb schematic of 2MB memory module? I ask because i would like to draw new pcb and i’m not sure where 2×2 gold pins are connected. Btw. It seems that power supply unit is faulty and cause malfunction of one of OKI M52998 chips – see distorted rectangle on the display. Double check capacitors and make sure that voltage levels are correct.

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  3. It would be great to get schematic of 2MB board. You’re right, i missed that part about the screen and leaked psu capacitors. I wrote about OKI chips because i fixed damaged panel some time ago by replacing faulty chips. In my case 3 chips were faulty, in your case probably only one chip is damaged and need to be replaced. OKI chips are available at aliexpress.

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  4. Wow that was very fast. Thank you. I will publish pcb when it’s done. Btw. Contact me (send an email) if you’re interested in fixing the display.

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    1. Hi Christian,
      To switch to external monitor you need to use DOS utility. I have it somewhere on the disk 😀 There is no other option to do that.

      I have got oryginal HDD but it is useless. To many not marked Bad Blocks…

      I used Compact Flash adapter with 2GB card and it is working perfectly. But you need to use EZ-DRIVE utility to prepare bootloader and format the Card. I also successfully tested SD adapter with 4GB card.

      I can prepare manual for both tools and share files.

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      1. Hi, I have recently acquired the ZEOS version of this laptop. Did you happen to find the utility to switch to external monitor? My machine currently has a dead backlight but otherwise in perfect working order. It would be nice to be able to actually use it with an external display until I can work out how to fix it properly.

        Regards

        Mike

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    2. Did you get anywhere with the PCB design? I was looking at having a go at putting one of these together myself as well

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  5. I have the same computer, but from Sanyo model MBC-18NB6h (the case and components are identical).

    I have a problem that every time I start up I get the message:

    “Invalid configuration information – please run setup program
    Press the F1 key to continue, F2 to run the setup utility”

    After entering the BIOS via the F2 key and saving the configuration I have the message each time:

    “SETUP has attempted to correct the following errors:

    * Standard CMOS checksum was invalid. Standard CMOS were loaded.
    * System configuration was invalid. Review the first page settings.”

    The CMOS battery is functional – the clock and calendar work.

    Does anyone know what the problem could be?

    Translated with http://www.DeepL.com/Translator (free version)

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