Tag Archive for 'zxspectrum'

ZX Spectrum update

Posted on December 25, 2009. 1 Comment

I’ve brought my spectrum to university today, they held a sort of computer technology history lecture there, it wasn’t really a lecture, but it was pretty interestring. There were 10″ floppies, and huge disk plantterns (used for data storage), and various old computer parts.

Anyway, I added an extra resistor to speakers, which made volume twice smaller, and now it doesn’t sound-rape your ears. I’ve showed it on small black & white TV I have, and the setup roughly looked like this (plus a laptop acting as cassette player to load from tapes):
IMG_1406

And here’s a small video, which has sound:

Oh yeah, I tried copying games from tapes to diskettes, but it seems they need to use altered game loader, which I didn’t start writing (but it should be fairly simple, most games just require to load their binary by specific address, and that’s all, in fact, most of the time it’s offset 32768, at least that’s valid for original JSW). The tape-to-disk copier looks like this:
IMG_1411

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ZX Spectrum RGB

Posted on November 8, 2008. 1 Comment

With some help I’ve accomplished the goal of few months – ZX Spectrum now runs and outputs image in COLOR.

Well, it’s not really done – right now only RGB and synchronization outputs are properly converted (to SCART). There’s still brightness output though, so it only displays 8 colors without shades.

Also cable is terrible, image quality is bad because of interference in the cable itself (it’s not isolated or anything, just simple 5-wire cable). You can see rounded edges, and a red stripe in the video below.

The cable:

That’s SCART. A lot of pins, for everything you could think of, but here’s what pins I used:

  • 21 – GRND (Ground)
  • 20 – SYNC (Synchronization signal)
  • 16 – BLNK (Blanking signal). Attached to a small 1.5v battery. There is no acceptable power source from Spectrum, and you have to input voltage here to switch from composite to RGB input/output)
  • 15 – RIN (Red channel input)
  • 11 – GIN (Green channel input)
  • 7 – BIN (Yellow channel input. No just kidding, it’s blue.)

Also it was fun when I made mistake of swapping BLNK (16th, RGB-COMPOSITE switch), and brightness output – it outputted only bright parts correctly, and the rest of screen was white…

Jet Set Willy was loaded from my laptop via sound output/tape input. The game works, except it’s copy of original, so I needed this nifty table to bypass copy protection (found on Wikipedia (look, it’s small picture doooown there):

Also notice the diskette inside. That’s my tapeloader diskette – it’s MS-DOS formatted, and therefore crashes ZX Spectrum, and it reboots in Sinclair ROM rather than TR-DOS ROM (TR-DOS works only for floppies).

Edit: Tape signal looks like this (square wave modulated by width, 300 bytes/second):

Photos:

Video:

(Yeah, that’s the kitchen, with the telly that is not occupied)

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ZX2

Posted on October 12, 2008. 0 Comments

So the power feed for 5 volts is missing, and source unknown. It’s too complex to take off the floppy drive (psu is under and near it), so the decision was to just connect it to a new power surge unit.

Motherboard taken off, sorry for horrible webcam, you can barely see the KR-something floppy drive controller. The 5-inch drive isn’t ibm compatible, but the power connector is compatible one, weird.

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ZX

Posted on October 11, 2008. 0 Comments

So I got my old fathers ZX Spectrum back from garage. But it’s no ordinary spectrum – it was built from scratch from parts, and technically it’s Pentagon modification with TR-DOS controller (yes, while rest of the world was using tapes, soviet people used diskettes).

Right now it doesn’t work yet, some problems in it’s PSU prevent voltage from getting to 5 volts (it outputs only 0.33 volts, which is just enough to slightly light up power led).

So I’ll be working on it, maybe I’ll get it to work soon.





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