VOGONS


XT/CGA laptop dissection

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Reply 22 of 100, by bjt

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Have been having a blast trying different games on this system. I also finally found a EMM driver that works with the C&T 82C100 chipset, it's the one that Robin4 uploaded with the Laser XT-3 system utilities: http://www.vogonsdrivers.com/getfile.php?fileid=640

This driver allows me to create a ramdrive in the top 384k to store commonly-used programs. With DOS 3.3 I still have 585k left after loading the EMM driver and ramdisk, which seems plenty.

Will probably upload a video in a bit showing various games running, playing MOD files and even driving my SC-55ST via the serial port.

Reply 23 of 100, by bjt

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Holy thread resurrect Batman!

With my other machines all sorted I'm coming back to this. I now have an Extron RGB 202xi video converter that should do a better job of the CGA->Analogue RGB conversion than my home-made circuit. Just need to make up some suitable cables and test it out.

First of all though, before I put this away last year I was still having intermittent problems with the battery light flickering on during disk access, and read failures to boot. This continued even when I replaced the floppy with the HxC emulator, so my next suspect was the power supply. Sure enough, some of the supply voltages were well out of spec.

The innards of the PSU. I can't see anything obviously wrong but I'm not about to poke around with that massive cap in there, so time to look for a replacement. Thankfully a kind soul posted a pinout for the power connector at http://www.actsirius1.co.uk/pages/docs/v86p_power.pdf. Note that I found Pin 1 to have voltage on it when I probed the original PSU, so I left it disconnected for the replacement.
NBpqu99l.jpg

The original PSU is 8.5V with fair whack of current, more than most cheap generic PSUs can supply.
jr0DrmAl.jpg

Luckily it turns out that a Playstation 2 Slim PSU is a perfect match, and these are available cheap on eBay.
FB4oQ15l.jpg

Glued the new PSU inside the old housing with a load of epoxy, it's not going anywhere.
Z4IhToAl.jpg

The final result.
cfcpmZal.jpg

Reply 24 of 100, by carlostex

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Amazing work mate. Your XT machine made me remember about the Halt and Catch Fire TV series. You are truly a resourceful chap, i will definitely be bothering you if i ever have the need. 🤣

Reply 25 of 100, by bjt

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Cheers! I enjoying messing with this kind of hardware. Amazing what you can get done with a multimeter and a soldering iron.

Currently working on porting the HxC Floppy Selector software to DOS, this is an app that can display an on-screen list of all the disk images on the SD card and allows you to "insert" them to drive A or B. Perhaps this will make the HxC emulator more attractive to PC retro users compared to the cheaper Gotek devices.

https://www.youtube.com/watch?v=p1zP6p9SBLw

Reply 26 of 100, by chinny22

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Missed this the 1st time round. Loving the mix of old and new like HxC Floppy, TV out. Could you use a CF card for a HDD?
Putting the PS2 adaptor inside the original was a nice bit of attention to detail.

Reply 27 of 100, by bjt

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The HDD interface is a weird 26-pin proprietary thing based on RLL I think, so a CF card is out of the question unfortunately.

Made some good progress on porting the floppy image selector. Doesn't look like much but it's parsing the FAT32 filesystem on the SD card correctly (DOS 3.3). Still got to get the image selection working.

6JWrySyl.jpg

Also bonus offtopic pic as it's right here on the camera, went for a walk in the hills on Saturday
AAiS5BKl.jpg

Reply 28 of 100, by badmojo

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Great project bjt! There's lots of fun to be had with a bit of imagination and persistence.

Nice pic of the countryside, love those old stone fences. A bit of persistence required in building those too. 😀

If it's broke, then fix it!

Reply 29 of 100, by bjt

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Found something else cool: although the built in BIOS only supports 720k drives, the on-board floppy controller (WD37C65) supports the higher data rates used by 1.44MB floppies.

There is a TSR called 2M-XBIOS which can piggyback onto the system BIOS to add support for HD floppies. Tried this just now and it works a treat, I can mount a 1.44MB image in both A and B. This will open up more games/apps that don't fit on a single 720k floppy image.

Obviously I can only boot from 720k image in A:, but once the TSR has loaded I can switch to a 1.44MB image.

More info: http://www.vintage-computer.com/vcforum/showt … sion-for-PC-XTs

Reply 31 of 100, by StickByDos

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Hello,

I've just seen your topic, I too have a V86P
Its hard disk is still working and it was still carrying the program to generate the reinstallation disks for Victor MS-DOS 4.01a french
It has EMS driver and an utility to switch grayscale dithering mode between 9 modes

Type win to loose the power of your computer !

Reply 32 of 100, by bjt

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Hi, that's great news. Could upload the V86P-specific files here or email them to me please?

These are quite cool little machines, do you have any plans for yours?

I have nearly finished porting the HxC floppy emulator manager to DOS, just need to tidy up the interface. I stuck to text mode so it will run on anything from MDA upwards.

Reply 33 of 100, by StickByDos

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Here are the files but hard disk has also files for others Victor laptops

On mine, battery still hold charge for 1 hour.
I wish someone could make a special version of XT-IDE for larger hard disk, hd controller is on a daughterboard that could be replaced and hd bios is on a socket on the motherboard.

There is a 60 pins extension connector on the back, I think it's ISA except power, that can be used for extensions.

Attachments

  • Filename
    V86P.ZIP
    File size
    8.08 KiB
    Downloads
    74 downloads
    File comment
    SXTEMM.SYS & GRAYSET.EXE
    File license
    Fair use/fair dealing exception

Type win to loose the power of your computer !

Reply 35 of 100, by StickByDos

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I didn't know this, thanks.
I've just tried and I discovered with C&T MIPS 1.20
CTRL-ALT-F7 4.77MHz (MIPS 0.22)
CTRL-ALT-F8 10MHz (MIPS 0.43)
CTRL-ALT-F9 Invert LCD
CTRL-ALT-F10 Switch off LCD

Type win to loose the power of your computer !

Reply 38 of 100, by keropi

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I am resurrecting this thread because of the cga->scart diagram posted by bjt: Re: XT/CGA laptop dissection

I have seen the schematics floating in the web and I assume this one is the best and without errors. What about that brown/yellow fix? What is it required so this becomes the ultimate converter?
Also since my CGA has a working composite-output, I think I won't even build the sync combiner part, it should make no difference to a crt if I use cvbs as sync.

I just got an XT setup but the monitor is a b/w one... it sucks and I am thinking of replacing it with a triniton 14" that also has separate composite input .

🎵Link to buy a PCMIDI mpu
🎧Orpheus soundcard project
💻WTB Amstrad PC7486SLC-33 system

Reply 39 of 100, by StickByDos

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According to to there, green intensity is reduced when color 6 is detected.

It can be implemented with logical gates circuitry, 4 inputs, 5 outputs, corresponding to CGA RGBI and an alternate green output with an extra resistor, that is used when color 6 is detected.

Type win to loose the power of your computer !