Spectrum Computing

If you're new to soldering, I'd definitely recommend practicing on something other than the Spectrum first. It's pretty easy to work on, with huge joints and tracks the size of your thumb, but Sinclair definitely skimped on the materials and the board does have a bit of tendency to fall apart while ...

The drop-in switch mode regulator has worked like a dream for me --- no heat sink, no heat, no problems. Strongly recommended!

I really like it when I find a problem that turns out to be caused by me doing something really dumb --- because it's usually very easy to fix. Turns out the Spectrum was just poorly calibrated, and five seconds' work with a screwdriver fixed it. It looks really nice on my Trinitron PVM monitor, and...

It does PAL and SECAM, with a switch. It also has lights to let you know whether it detects colour. Interestingly, if I route the video through an CV-to-HDMI-to-CV cover I get nice vibrant colour and the PAL light lights up. Connected directly I get mono and no light. This suggests that the monitor'...

My nice new Sony PVM has arrived! The Spectrum displays in mono on it. It displays in colour on two out of my three composite-capable LCDs (the third is a big-screen TV and just shows black). I was kinda expecting a real CRT to do better than a modern LCD. Is this behaviour symptomatic of anything? ...

I don't think 'pedestrian' is the right word --- that implies it's somehow ordinary, which ZX81 Basic is anything but. I think my favourite combination of features are the absence of multiple statements per line and the missing ELSE clause in if statements: these synergise beautifully for maximum in...

Oh, yeah, I completely forgot you could do that! Except it didn't save the GOSUB stack along with the program state, hence the warning in the manual... Gosh, I'd forgotten how... opinionated... ZX81 Basic is. Also slow. Incidentally, several of the programs in that issue of _Sinclair Programs_ are i...

So ZX81 Basic, unusually, allows modification of the program without clearing all the variables; and SAVE and LOAD will save them and reload them. Except, RUN implicitly does a CLEAR, wiping them before the program runs. Given that the ZX81 does (AFAIK) allow autorunning of programs, how does this m...

Or maybe, and bear with me, I know this is a long shot... maybe I could just connect the composite decoupling capacitor the right way round? Okay, so I also added the transistor mod, so maybe that made a difference too, but all the monitors I've tried this with are quite happy now. (Although the ins...

Thanks for the links; all useful. The transistor mod is simple enough I may just try it, and see what happens --- it can't make things worse. It's still really weird that there's no sign in the scope of anything wrong. The timing looks fine (64us per scanline). The voltages look fine (1V from the bo...

Well, I fired it up today on the capture card with the intend of typing in my colourbars program and tuning it; and was met with black. There was signal there, but the capture card wasn't showing an image. The machine still works and still shows (glitchy) images on the other devices. So whatever's c...

Way ahead of you own the TV settings, sorry! Image 'enhancement' filters drive me nuts and I always try to turn them off... But there's something more than that going on. I'm trying to source a real composite CRT and see if that's any better. I hear that the ZX81 omitted various important parts of t...

Woohoo! https://s15.postimg.cc/g9357ou4n/my_photo-2.jpg I own a really very nice Tektronix 7603 oscilloscope weighing 13kg, so calibrating the video was a cinch --- thanks for the links; I'd never have thought to do it otherwise. However... I have a mini composite monitor, which won't even admit the...

Hot water and a iFixit-clone stainless steel spudging tool worked reasonably well --- I managed to get most of the lumps off. It'll lie flat now, so I think I'll leave it at that, as it's good enough. Man, that glue is repulsive. I actually tried a nylon pot scourer thing, and the nylon came off on ...

I did actually use a water bath to get the faceplate off (it wasn't like the old membrane could get any more broken!); I'll have another go. I have a soft plastic spudger that'd be ideal for scraping. Apparently IPA isn't a good idea because it can discolour plastics. I can't find out what the plast...

Status update: caps replaced, though I cocked up and I might need to replace some again --- I'll find out when I try to put reassemble later; replacement membrane is here and I've disassembled (and cleaned, ugh) the old keyboard; TRACO regulator should arrive tomorrow. Kudos to RWAP for delivering t...

Yeah, the Acorn MOS is a bit of an unfair comparison; having 16kB BASIC + 16kB OS was unheard of luxury back then (and went a long way to explaining why the BBC Micro was so special, and so expensive). A better comparison is the Commodore 64. (Also supported by Cowgol! https://pbs.twimg.com/media/DO...

Well, that was anticlimactic. var i: uint8 := 10; while i != 0 loop print("I can do it "); print_i8(i); print(" time"); if i != 1 then print("s"); end if; print_newline(); i := i - 1; end loop; ...compiles to: https://s15.postimg.cc/x3b1xys0n/screen.png The binary is pr...

Note that I rewrote my last post to be less obviously frustrated --- sorry about that. I'm used to the BBC Micro, which has a significantly more complex operating system (like, it actually has an operating system). The Spectrum's so much simpler, better understood and has such a larger community tha...

Again, there are no “universal” entry points—each programmer uses mostly arbitrary points based on his particular needs. [...] Those tutorials you refer to, simply use a subset of “most commonly used shortcuts” to ease a novice into programming in languages other than Sinclair BASIC. Yes, precisely...

Re not wanting to do this much --- so far every single Spectrum machine code tutorial I've found has used the Basic entrypoints for drawing on the screen; plus I've found two different Forth interpreters which do it, for all their I/O; plus a Pascal interpreter which does it; etc, etc... although in...

I don't have an assembler. My compiler generates binaries directly. I already know how to turn these into loadable TZX images which can be used on emulators or real hardware; that's not the difficult bit. I know that the huge list is a disassembly of the entire ROM, which is why it's not very useful...

So I've got this compiler: http://cowlark.com/cowgol/ It's a self-hosting fully compiled language for the Z80 and 6502, where the Cowgol compiler is written in Cowgol and you can (technically; it's far too slow to be feasible) rebuild the compiler on the target machines. Now that I own a mostly-work...

Nothing looks particularly explodey in the power supply, but it generates about half the voltage it should; it's got two 1000uF capacitors and a single 2200uF one, all in parallel across the output lines. Wow. It's been a while since I've seen a PSU quite this primitive. Naturally, my parts drawers ...

Good to know; I'll stick with the regulated 9V supply. I think I'll attempt to repair the original power supply brick, but I suspect it's going to spend its time on a shelf somewhere.