Compaq Contura 3/25C 80386 Laptop

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I recently picked up a free Compaq Contura 3/25c, a very old IBM-compatible laptop computer from the early 1990s, with a 25MHz 80386 processor, 4MB onboard memory and 3.5in 1.44MB floppy drive. The original 120MB hard drive has been removed by the previous owner. The laptop is also in very bad shape, with dust all over the place and the LCD panel removed:

The laptop must have looked like this when new with the 8.4 inch black and white LCD:

I was trying to make it boot up by connecting an external monitor to the VGA port when I noticed that the VGA port is actually keyed via pin #9. No modern VGA cable would fit into this port until you break pin #9 on the cable or punch a hole on pin #9 of the port. Since there is actually no need to key a VGA DB9 connector because the shape of the port would prevent you from inserting it upside down anyway, later VGA ports used pin #9 as an optional +5V DC source.

CMOS Battery

The unit boots up with a “RTC Lost Power” error message (see this for a full list of Compaq POST error messages). This is quite common with old laptop when the CMOS battery finally dies after a few years. So I opened it up in order to replace the battery:

The laptop is using a CR2430 lithium coin battery placed in a socket to facilitate replacement. There is even a warning, in various languages, telling you about danger of explosion if the battery is incorrectly replaced. This surprised me, since modern laptops would probably just have the battery soldered onboard. Some may feature a motherboard socket for the battery connector, but the actual connections to the battery are permanently soldered, which means some wire-cutting and soldering needs to be done if the battery ever needs to be replaced. This is a CMOS battery from a newer laptop:

I quickly ordered a pack of 5 CR2430 cells for a cheap price from eBay. Notice the funny English on the packaging. Whoever typed this probably had no ideas what it means:

BIOS Setup

With the CMOS battery replaced and a PS2 keyboard connected, I started the machine. Although many old laptops and PCs do not have an onboard BIOS and require the use of startup disks containing the BIOS utilities to change system settings, this machine has one, available in several languages, accessible via F10 at startup:

There are 2 startup disks for this laptop, formerly downloadable from Compaq website:

  • Disk 1: BIOS setup utility
  • Disk 2: Diagnostic utility

However, these downloads were removed when Compaq was merged with HP in 2003 and a lot of legacy support was gone. Although I eventually managed to find the disks with the help of, disk 1 comes with no COMMAND.COM and boots up to a DOS error “Bad or Missing Command Interpreter” error message. I fixed the error by putting MS-DOS 6.22 on it. The images for both disks as well as the original tool to create the disks (SP2054.exe) can be downloaded here. You will need WinImage to write the images to floppy disks.

Unlike the motherboard SETUP, the SETUP utility on the disks uses graphic mode and takes a long time to start up:

Installing the hard drive

Since the original hard disk has been removed, my next task is to install a 2.5inch IDE hard drive before the notebook can be used for anything useful. Keeping in mind that laptops of this generation only use CHS addressing and do not support hard drive more than 512MB due to the 1,024 cylinders limitation, I have chosen a 270MB IBM DHAA-2270 hard drive:

Still, installing the hard drive turns out to be no easy tasks as the BIOS only supports a limited number of hard drives types (which does not include my drive). There is also no support for auto detection or user-defined types:

Interestingly, types 65 and 66 are empty, indicating that they are custom types and can be configured by either re-programming the BIOS as suggested in this forum discussion, or by writing a tool that modifies the BIOS hard disk type table stored in memory and hope that the BIOS will recognize the changes. Either way, it’s a shoot in the dark as I could find no instructions on flashing this laptop’s BIOS, and there is also no documented address where I can hope to find the type table.

However, there is an easier way by using a drive overlay such as ANYDRIVE or EZ-Drive. The trick is to specify a hard disk type in BIOS where the number of cylinders, heads and sectors is smaller than the actual value so that the BIOS will not report an error on POST and accept the hard disk. Once then, boot from a floppy disks with ANYDRIVE to set up the disk overlay, which will overwrite BIOS Int 13h (which is used by DOS to query hard drive info) and respond with the correct disk geometry values. Run FDISK to setup the hard disk and you will be able to use the full capacity.

This will work with DOS and Windows 3.1 or older which relies on Int 13h to access the hard disk. Operating systems such as Linux and some disk utilities may query the hard disk directly, resulting in possible data loss with the overlay installed. In Windows 3.1, 32-bit disk access must be turned off, otherwise Windows may also query the hard disk directly, resulting in similar problems.

Transferring files using Norton Commander

With the overlay installed, all existing data on the disk is lost and some PCs may also fail to recognize the drive. Since I do not want to copy data and programs to the laptop using floppy disks, the only other way is to use a serial or parallel cable, with the help of Norton Commander 5.0 Link utility.

Note that you cannot simply use a male-to-male serial or parallel cable, but rather a null modem or a Laplink cable respectively. Since these cables are extremely over priced, I decided to go for soldering a null modem cable myself using the connectors available in my junkbox, and the pinout from here. With my other PCs running Norton Commander (NC) from within Windows 98 acting as Master, I am able to copy the data to this laptop (acting as Slave). At a maximum theoretical speed of 115200bps, made slower by the noise-sensitive cable disrupting the copy process resulting in several misleading errors “There is not enough room to copy…” from NC, it took half a day to copy DOS programs, games and Windows 3.1 to the laptop.

However, before I could think of some useful purposes for this laptop, it dies and fails to POST with no beeps and no display output. On every boot, the system simply hung after attempting to seek the floppy drive. There were perhaps several symptoms that the laptop was dying, for example the fact that I needed to press the POWER button multiple times (although the button itself is fine, as checked by a multimeter) to turn the laptop on and the wrong memory count of 21885KBytes extended memory in BIOS:

Since all basic troubleshooting does not seem to help and there are no user replaceable parts inside the motherboard, I eventually removed the hard disk and ran FDISK /MBR to remove the overlay, and toss the machine. Everything has its time, I guess.

UPDATE (Feb 2014)

A reader shared with me that he had a similar Compaq Contura laptop whose LCD had failed and displayed random patterns upon being turned on, although it still seemed to boot properly as the POST beep could be heard. After several debugging attempts, he finally managed to fix the issue and the laptop could boot to Windows 3.1 successfully. The LCD failure was due to a broken PCB trace resulting from an electrolytic capacitor leak (see the comments section of this article for further details).

The complete set of photos and videos demonstrating the disassembly, the failure mechanism of the LCD as well as several Windows 3.1 screens once the LCD has been fixed can be viewed here.

Thanks to Fabio for his sharing! I am sure this will help other people who are trying to keep their Contura laptops and other similar vintage computers alive.

4.00 avg. rating (84% score) - 1 vote


A tough developer who likes to work on just about anything, from software development to electronics, and share his knowledge with the rest of the world.

24 thoughts on “Compaq Contura 3/25C 80386 Laptop

  • January 11, 2012 at 8:26 pm

    This was my first laptop purchased circa 1995 when I was in my final years in the U. It's with a color display. At that time running on Windows 3.11.
    Loved that trackball though looked awkward at that time, it was easy to use.

  • January 25, 2014 at 7:14 pm

    Hello, I do not have the floppy drive for this contura 325, can you do an image of the hard disk for me? Thank you.

  • January 25, 2014 at 10:42 pm

    HI Fabio,

    I do not have the HDD image of this computer. You should be able to get MS-DOS 6.22 and Windows 3.1 on it without issues. You can get many old boot floppy disk images from

  • January 28, 2014 at 5:10 am

    Thank you for your attention, but I do not have the external floppy drive for contura 3/25. It is a special PCMCIA to floppy card.

  • January 28, 2014 at 10:17 am

    Hi Fabio,

    As a start you may want to put the HDD into another computer and put MS-DOS on it (via the SYS command, for example), together with other software and utilities. Once the hard disk is installed back to the laptop, it should be able to boot into MS-DOS, from which you can install Windows 3.1 and play with it.

    Have fun!

  • February 15, 2014 at 10:33 am

    Thank you for your advice. I bought an another contura with bad lcd screen, and it came with a pcmcia to floppy drive. I found two new boxes of 1.44MB floppy disks for sale, and now I am able to enter setup. Whoa! The contura with broken LCD has a working hard drive, and it boots up with a windows 3.11. With two conturas I did one, working very well. Only the hard disk drive seems that have some click sounds, maybe it will be dead soon. I only want do preserve the old technologies, because these items become very rare as the time goes by.

  • February 15, 2014 at 10:36 am

    Hi Fabio,

    Thanks for sharing :) Enjoy playing with the laptop. Let me know if you need any files or old software to play with.

  • February 18, 2014 at 1:58 am

    Okay, thank you. Now I am looking for a LCD screen for compaq Contura 3/20 (386 20MHz). Everything is fine but the screen. It does turn on, even the backlight turn on. But it shows only some big squares, like a chessboard. It is a monochrome vga display. I tried to disassemble it, tried to wash and dry the circuits (I have a lot of luck washing old circuits and then putting it in an oven to dry it) but it still does not work. The display works with 28 Vdc and this voltage is present, then I think is it dead. (its not broken). If you know how to fix it, can you advice me?

  • February 18, 2014 at 10:34 am

    Hi Fabio,

    How does the chessboard pattern look like? I can give some ideas if you can send me a photo of the LCD displaying squares and a high-res photo of the motherboard.

    Can you connect the VGA port at the back of the laptop to a monitor to see if you can have a video output? If so, the video controller is working fine and the problem may be with the LCD driver.

    If the backlight turns on and the DC voltage is correct and the LCD is not broken but only shows a chessboard pattern, try to identify the LCD controller/driver chip on the board. If you can identify the chip, try to search for the datasheet. Some chips have a test mode which will output some test patterns on the LCD. Usually, this mode is activated either by shorting a dedicated pin to 5V/GND or when some input signals are missing. If you can locate the controller chip, try to identify any short circuits. Old dirt or leaks from electrolytic capacitors on the board may have shorted something and enabled the test mode.

    With the laptop and LCD on, use a thermal camera or a cheap cellphone camera in video mode and point it close at the motherboard. Any shorts will result in heat and may be visible in the camera viewfinder. I used to identify shorts on old circuits this way.

    Last but not least, check the ribbon cable from the motherboard to the LCD. Tiny metal traces on it may have been broken after numerous opening/closing of the LCD panel, causing problems.

    Let me know your progress.

  • February 18, 2014 at 12:04 pm

    Hi MD. I did all your tests. I did test the flat cable before, and yes, there is video output in VGA port. Everything works fine.

    The backlight does not turn on, but This is a different circuit, isnt it? Maybe the cold cathode lamp is dead. Since you asked, I have never de-solder the flat cables inside the LCD. I had to do it to see the part number of the ICs, because they had a plasic housing over them. I disassembled everything and took photos and did make a video, they are here on my dropbox:

    As you can see in the video, the pattern is different everytime I turn the LCD on, not always the same. I found only the voltage multiplier datasheet, the other one I did not find (50003scc-s). I trie to resolder everything, but nothing seems to fix it.

    3/4 of the LCD borders have some ICs mounted over the flat cables, I thnk they are demuxes to excite the LCD pixels. You can see that the chessboard pattern seems to be mounted every demux, like some demuxes send blach and some demuxes sends white. can you notice that in the picture 2014-02-17 00.13.12.jpg?

    I measured the voltage over the capacitors, it has about 24.. 28V over them, some of them have 2V.. There is no test/example circuit on datasheet to show what voltage need to be on the capacitors (

    Thank you for your patience.

  • February 18, 2014 at 1:29 pm

    It is working now! I was checking the inverter circuit that turn on the LCD, and there is two potentiometers. One of them have 2V reference, and the another didn have this 2V reference. I checked the tracks and the track that brings the reference was broken due a eletrolytic capacitor leak. I just solder the two broken tracks and it did turn on! Check the last photos in my dropbox:

    There is still two lines that do not turn on, you can see at the photos. But there is no problem.. BUT if you know how to fix it.. :)

    Thank you very much, you were right. \o/

  • February 18, 2014 at 2:11 pm

    Hi Fabio,

    Thanks so much for your fast update and congratulations on getting this old machine working again. :) Your photos and your video are great too – it has been a long time since I last saw Windows 3.1 and MS-DOS on a monochrome LCD.

    After reading your first reply and looked through the photos, I did some research on the LCD panel of this laptop and managed to find some valuable information. I posted here in case it may be useful for others.

    The laptop is using the LM64P728 (139638-001) VGA panel. It is using the 65540/65545 integrated controller which will provide both output on the VGA ports and the LCD panel. The control interface is via a 15-pin connector (which can be seen in a few of your photos) and the communication protocol is shared between several other similar LCD models including the LM64P722 and LM64C08P made by Sharp.

    You can find the pinout of the 15-pin connector here: – it is for the LM64C08P but will be applicable for the LM64P722 and the LM64P728 too. The datasheet for the 65540/65545 VGA/TFT controller can be found here – it includes details about the communication protocol – which will be useful should you need to repair it again.

    Another company named RTD also created the CM110/CM112 controller, similar to the 65540/65545 controller. The CM110/CM112 supports the LM64P722 and LM68P728, together with many other color LCD panels too. You can find the datasheets below:

    A set of DOS tools were created by RTD to retrieve the LCD information and some diagnostics information. You can download it here – if you have time try it on your machine to see if it will work :)

    As for the 2 dead lines on your photos, it could be that the liquid crystals inside are already dead or inactive after a long idle period. Try to toggle the whole screen between black and white repeatedly and leave it like that for a while – it may revive the liquid crystals inside those pixels if they are not totally dead yet. Also use an oscilloscope to check for ripples on the power supply – it may cause problems with the sync signals, resulting in the loss of some lines. The latter case is however unlikely as your dead lines seem to be at fixed position.

    Again, great work on this laptop and thanks for sharing with me too!

  • February 18, 2014 at 8:43 pm

    Thank you very much for your research and your effort to help me. I have 3 contura laptops: 3/20, 4/20 and 4/25. The 486 are color displays and the 386 monochrome. The 386 disk have no badblocks, one 486 has a dead hard disk and a dead screen. The another 486 is working well but has a "clicky" hard disk. I am repairing and will keep these old computers in a special box, to prevent their contact from high temperatures and humidity.

    About twenty years did pass from the manufacture date, and I pretend to keep it a lot more, to show my grandsons how was the technology from the past.

    I will continue to search and buy for a few bucks all of these old machines. Please send me an e-mail to to keep in touch.

    Feel free to use my images to put on your blog, or if you need some pictures (even disassembled), I can take for you of the working system. It is very interesting.

  • February 18, 2014 at 9:07 pm

    Hi Fabio,

    Thanks so much for sharing too. Let's keep in touch. I will also continue to update my blog as and when I find interesting old machines to play with. :) It is great that you are maintaining these little old machines – they are made to last decades!


  • March 24, 2014 at 5:56 am

    This was an amazing read! I myself have two of these laptops, a 3/25 and a 4/25, both are defective. I bought the 3/25 as a parts machine for cheap, but as I hate to strip machines, I decided to keep it and fix it up. It is missing the keyboard and the cover, and the ribbon cable to the display is broken. Of course it came without a harddrive too. ;-)

    However, it does seem to boot as I can hear the BIOS beeps through the PC speaker. I did not yet try to connect it to an external display because of the keyed VGA port, as described here.

    I got the 4/25 later, it is complete but has a broken keyboard and power board, I tried it with the 3/25's power board and it boots fine to Windows 3.1 with an external keyboard. :-)

    These are great little machines, cheers to everyone who tries to keep them alive!

  • March 24, 2014 at 8:44 am

    Thanks for sharing with us. I love these little old laptops – they are great machines for experimenting with DOS and Windows 3.1. Let me know if you manage to get your 3/25 to do something useful after fixing the keyed VGA port :)

  • March 25, 2014 at 1:49 am

    I am glad to tell you the system is working! Today I attached it to an external display and it passes POST perfectly, except for the oh so familiar "RTC Lost Power".

    I tried a fix for the ribbon cable that consists of cutting off the broken connector, and then carefully sanding off the plastic insulation layer to create a new connection point. After doing so, the display lights up and the brightness/contrast sliders work fine, altough nothing appears on the screen. However, now that I know that the internals of the laptop are still OK, I'm confident I'll be able to fix that.

    I might eventually dedicate a website to these machines, so far I found out quite a bit that might be useful to other users and tinkerers alike.

    I'll keep you posted!

  • March 25, 2014 at 10:08 am

    Glad to know that your 3/25 is still in good health after so many years. Have fun with it! Let me know once your website is up – I will post the link to your website here for the benefits of others who are also interested in keeping these old machines alive.

  • May 4, 2014 at 9:07 pm

    I have one of those laptops, and the trackball i hate. I pretty much hate it because the mouse disappears whenever i move it. And, mine also runs Windows 3.11. I am booting it right row. (man those obnokios noises)

  • August 4, 2015 at 4:13 am

    All good day, I have a similar laptop, there was a problem with the dc-dc converter. electric diagramm be found anywhere else on the Internet can’t. At the moment I want to re-start the laptop HDD works audible as he reads the information, the monitor will not display information (no backlight). Can you help me? it is possible to measure the voltage on the 20 pin connector dc-dc converter? Not having electric diagramm very difficult to repair. Maybe someone knows where to apply power to enable the controller of the external monitor?

  • August 4, 2015 at 10:21 pm

    Hi Andrei,

    What do you mean by the dc-dc converter? If I understand correctly, your laptop screen backlight is faulty and you can’t read what is displayed on the internal LCD panel? Is there BIOS POST beep, floppy seek and hard disk activity sound after you boot?

    For the external monitor I think the default is to output a copy of the display on the internal LCD onto the VGA port. I will be 640x480x256 colors. Just use a standard VGA cable and see if it works. You may need to break pin #9 on the VGA cable as it’s keyed on the VGA port of this laptop, otherwise the cable won’t fit in. If there is no output on the port, it is possible that VGA output is not enabled on this port by default and you will need to press some keys on the keyboard. If that still doesn’t work, refer to the previous commented dated Mon. Feb 17, 2014 on how to debug the 65540/65545 VGA controller chipset – you can try to ground/connect certain pins in order to activate VGA output or display test patterns.

    You can refer to section 6 of the table (UPDATE (Feb 2014)) for some further information regarding LCD troubleshooting – a previous reader has contributed some useful diassembly videos/photos.

    Let me know if you need any info.

  • August 6, 2015 at 1:02 am

    Good day. thanks to which I replied, really want to restore this laptop.I got the laptop from the previous owner, he claims when he clicked to enable it, then heard the hiss with cotton in the top right of the laptop (that’s why I started the repair with dc-dc Converter: after you turn not, you will hear how the hard drive reads anything and everything. here is a picture Board of your monitor with comments: , the given image motherboard (reverse side): I now look carefully the previous posts, and do a similar action. I certainly doubt that the faults can be the same. I will be very grateful if you help run a vintage laptop. Wife told me I was a maniac :)

  • August 7, 2015 at 10:33 pm

    Hi Andrei,

    Thanks for sharing your progress with me and thanks for posting the detailed schema of the DC to DC converter and the disassembly photos. I have some suggestions below.

    A hiss from a power supply, in this case, the DC to DC converter, usually indicates that it is overloaded by a fault and operating at a lower frequency, hence causing the audible hiss sound.

    The most likely suspect I could think of is capacitors. Since you have replaced the through-hole electolyte capacitor and it still doesn’t help, perhaps there are other leaking capacitors as well. Do you have an ESR meter? If so you can check other capacitors, take note of the SMD electrolytics capacitors too – they have short shelf life and can leak without any visible effects.

    My experience with early laptops is that usually the VGA port outputs a copy of the internal LCD upon boot up without the need to press any key (Fn, etc.). In you case I think the problem of no VGA output is due to a hardware fault, rather than the requirement to press soft keys.

    The microcontroller / VGA controller on your photos usually have pins dedicated for the oscillators, do you perhaps have an oscilloscope or a frequency counter just to check that they are operating? If you have one you can also check the voltage rail (+5V, +3.3V) to see if it’s clean or contains ripples. Old capacitor may cause too much ripple on the voltage rail and affect the electronics. Meanwhile let me try to find the datasheet of your VGA controller and see if it could offer any help.

    The SMD10P05 MOSFET may not be faulty. I think the behaviour could be because of other components in the circuit. MOSFETs are unlikely to fail unless they were abused (subject to high voltages, etc.)

    One last suggestion, have you tried cleaning the board with a can of compressed air? This may blow off dirts, electrolyte leaks, etc that short the PCB tracks. It worked for me before in one of my old laptops.

    Again, thanks for sharing the detailed notes and keep me updated on the progress.

  • May 31, 2017 at 5:09 pm

    thanks ! i wake up an old 3/25 with your informations

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