Tony's Tech Archives

Tech Archives Page created May 2008. Last updated March 2020

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The snippets of information I've gathered on this page is mostly difficult to find info for old platforms and software. If you have any suggestions for improvement or spot any mistakes please let me know! Unfortunately I may not have time to answer individual queries, I would suggest trying the forums such as those on CPC Zone and Amiga.org for help. Although I have tried to give accurate help, anything carried out from following the instructions on this page is done at your own risk - bare in mind doing anything with very old hardware is always precarious!

DOS/WINDOWS: Formatting a floppy disk to 720Kb in Windows XP

Just about any floppy drives you'll still find these days are almost certainly going to be high density (1.44mb) but if you're formatting a floppy disk for a retro system to read (eg: Amstrad NC200 or Amiga PC-Task) you'll probably need to format it in low density 720Kb.

To do this from the command prompt in Windows, type in:

FORMAT A: /t:80 /n:9 /fs:fat

Additional notes for non-NT Windows versions (95, 98 etc):

- You can add /S to the command make the disk bootable.
- Drop the /fs:fat part of the command - it can't be used / isn't needed

Update: As an alternative to floppy drives for the Amstrad NC200, take a look at this modern solution from Simulant.

AMIGA 500: Installing a new hard disk in an A500 GVP HD+

The GVP HD+ is a popular hard drive expansion for the A500, and one of the best. It's a sidecar type unit and typically supplied with a hard drive of around 50MB when it hit the shelves in the Amiga's heyday. It's possible to put a much larger disk in the unit, providing it the same type of SCSI disk. Unscrewing, removing the disk and swapping over is straight-forward.

The next stage can be slightly trickier. I'm unable to document the whole process step by step but I've made a few pointers to help avoid the pitfalls I made:

If like me you started off without the software for the unit, an internet search should reveal some download locations for the software. Here's a couple of links at the time of writing:-

Amiga Resource
Installer's Heaven

- In order to correctly partition and mount the drive, make sure you boot your Amiga from a Workbench v1.3 (or lower) disk. My A500 has an upgraded 3.1 Kickstart and I spent some time trying to configure the drive from a Workbench 3.1 environment, which just doesn't work!
- Use the GVP utilities to partition and mount the drive. If like me you want to install something higher than Workbench 1.3 as the OS on the disk, choose No to install files from floppy.
- You can now install the OS from a dedicated install disk and proceed from there.

81: Fitting a ULA heatsink

Installing a ULA heatsink into a ZX81 is a quick and easy project that should reduce the internal temperature of one of the key chips that is prone to getting hot, and therefore extending the life of your ZX81.

I bought mine from The Sinclair Shop but they may be available elsewhere.

Once you've have the back off the ZX81 don't loose those screws and rubber feet!

You'll need to unscrew the circuit board from the other half of the casing. Be very careful of the attached ribbon cables to the keyboard - they are likely to be very brittle!

Board's out! The ULA should be clearly visible - it should be marked as so and is the nearest chip to the video out. The heatsink should fit comfortably over the chip, covering it's entire surface. Job done, now to find those screws!

Here's my ZX81 happily running after its small modification!

ZX81: Loading programs from your PC soundcard

It's official - cassette decks are finally obsolete! With nearly all ZX81 games now available on-line you can use most ZX81 emulators like EightyOne to play the wave file through your computer's sound card and straight into the ZX81. Of course you'll still need to experiment with sound levels but you've got it right it should work well as you'll have a clean input unlike fuzzy old tapes. Providing you have an emulator, some downloaded programs and a soundcard in your computer, the only extra thing you'll probably need is a stereo to mono adapter. A suitable adapter should have a stereo male end to plug into your sound card and a female mono input to plug your ZX81 cassette lead into.

You don't need a particularly powerful sound card - I'm just using the built in sound on my Dell laptop and it works just fine. The adapters should be cheap enough to pick up from electronics stores or somewhere like eBay. You shouldn't need to pay more than a couple of pounds for one, but don't forget to get the right size jack sockets for your soundcard / ZX81!

Amstrad CPC: Replacing an Amstrad CPC 6128 drive belt

Unfortunately I carried this out some time ago and didn't take any photos of the procedure :(

There's similar drive belts available for Spectrum +3 and Einstein computers too.

If you've dusted off your CPC6128 or have bought a second hand machine there's a strong chance the computer cannot read the floppy disks. You'll notice power to the drive but it simply cannot read the disks and returns a read failure. It's a very common problem and just down to the fact the rubber drive belt looses it's tension after a number of years.

Opening up the 6128 casing is very straight-forward via the screws on the underside. Once you open it up be careful of the connected cables - they are likely to be brittle. Looking at the disk drive unit you should be able to see the drive belt and although a little fiddly it can be gently removed and replaced with your replacement belt. Check the belt turns ok before putting your 6128 back together.

I bought my drive belt from John King's CPC/Spectrum/PCW website where you'll also find some superb tutorials, photos and diagrams to help. The belts are available elsewhere though, you'll also find them at The Sinclair Shop and searching Google and eBay will probably reveal other options.