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What’s that? It’s Retrochallenge time again?

Victor V86P

I'm sure pretty much everyone in the retrocomputing world would agree when I say that nostalgia is a major driving force in the hobby. Everyone has their own stories about the systems in their collection: maybe it was their first computer, maybe it was the system they had at school, maybe it's something they drooled over at the time but weren't able to get. For Retrochallenge 2017/04, I thought it would be good to have a trip back to revisit one of the systems I regretted selling when I was a teenager and subsequent adventures with a replacement.


It’s all been a bit quiet

So apparently I set this up, and completely failed to keep up with posts. I've got a bunch of things I intended to write up, so if you're one of the few people who comes across this site, there'll be some more content soon - I hope

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Sorry? I can’t hear you!

The original ZX Spectrum was typically connected to a portable audio cassette recorder to load and save programs. Later on, Sinclair released the Interface 1 with the Microdrive, a miniature tape interface that wasn't the most reliable (possibly a post on this at some point in the future). Several third party vendors released disk interfaces with varying degrees of popularity. For the most part though, tape was the the format software came on.

As time progressed, and every other system was already using disks (or so it seemed), Amstrad decided to try and breathe some new life into the Spectrum by releasing the +3, with its built in disk drive. Possibly too little too late, and probably not helped by their choice of format, the +3 was the last of the Spectrum line.


Adding composite video out to the +3

Now I have a working power supply for the Spectrum +3, I need some way to see what's being output. In its original configuration, video is output either a PAL RF signal on UHF channel 36 (UHF 36 was used a lot like VHF 3/4 in north america) or as RGB on the Peritel socket. The RGB signal doesn't help much here - whilst in the UK, TVs have a SCART socket with RGB inputs, in north america, TVs have YCbCr component inputs, so some circuitry to do conversion is required. That being said, the RF signal is generated from a composite signal - in earlier model Spectrums, it's just a matter of disconnecting the input to the modulator, disconnecting the output of the modulator from the socket, and connecting the input to the socket. Unfortunately, with the later model Spectrums, Amstrad mixed in the audio (as an FM signal), and that tends to upset TVs when you include it on the composite video input.


Replacing the ZX Spectrum +3 PSU

Seeing as the A1200 PSU replacement went so well, it was time to have a go at the ZX Spectrum +3. Much like the A1200, this also requires +5, +12, and -12V rails, with a similar sized casing (slightly wider and shorter). The original PSU was linear with a big, heavy, transformer - not ideal when you're trying to keep weight down for shipping. As a result, I'd already opened up the case and removed the existing supply before shipping the system. What I had in front of me was an empty shell.


A timely reminder

We all make regular backups, right? These days, it's easy to setup something largely fire and forget - things like crashplan, backuppc, timemachine, etc. What about our older systems? Making a working copy of your disks used to be standard practice; likewise saving your important files to more than one disk. How about backing up hard disk based systems? Sure, there was software out there to backup everything, but unless you had a tape drive you needed to use a lot of floppies. I remember backing up my Commodore A590 wasn't too bad - it was only a 20MB disk, and writing out to 880kb floppies meant you only needed 15-20 disks. When I got my A1200 with it's massive 60MB disk, I don't recall if I ever did a full backup - after all, I had all the programs on floppy, and I had my data backed up on floppy. Even if I had a backup from the last time it was in use, it wasn't in amongst all the disks I brought over with it. Nor, it seems, were any of my workbench disks. I'm sure you can see where this is leading.


Replacing the A1200 PSU

So January has rolled around and all my stuff from the UK is still sitting in the basement untouched. January is Retrochallenge time - I had intended on working on my 48k Spectrums, but I don't think that's going to happen for a while yet. However - getting my A1200 and +³ up and running seems like a good start.

My A1200 was purchased, second-hand, for a friend at highschool as a replacement for my much loved A500, which by the mid-90s was getting a little long in the tooth. The A1200 represented quite the upgrade, going from a 68000 to a 68EC020 and it had a massive 60MB hard disk (compared to the 20MB I had in my A590). If memory serves, it set me back £60 - which without a job is rather a lot. It was my main machine for a while, before I got my first IBM PC (we had a family PC for quite some time), but that's a story for another post.


Unpacking the big box of goodies

Twas the day before Christmas and all through the house... Ok, maybe not - but it was Christmas Eve when the movers appeared with my big box of toys. As you can see, it didn't quite fit under the tree 🙂 With family descending on us the following day, I thought it would be a good idea to unpack it, take it downstairs, and snap a few photos in the process.


Retrochallenge 2016/01

As I'd mentioned in a previous post, when we were over visiting my Mum last year, I filled a 4.5cuft box with fun bits and pieces from my childhood, including my Amiga 1200, Spectrum +3, and two 48k ZX Spectrums that aren't very happy. Well, the box arrived on Christmas Eve, just in time to go (almost) under the tree.


My love-hate relationship with pre-lit trees

It's that time of year where we start to pull out the Christmas decorations. Now before you start, yes - I know it's only November, but when you have six trees to put up and decorate along with all the other decorations, you need to start early. If you've looked at Christmas trees in the shops recently, you'll see that there's a big trend toward pre-lit trees. If you haven't, the idea is that instead of having a long string of lights in a box that you have to slowly unwind onto the tree, the tree has several strings of lights already attached to the branches so all you have to do is fluff the branches and plug it in.

Incandescent Christmas lights are pretty neat little things. They're not just a simple filament bulb - they also have a shunt which is intended to short out the bulb in the event that the filament breaks. This means that when you have a long strand of bulbs wired in series and one fails, it doesn't cause the whole strand to go out. It usually works, but not all the time. As bulbs fail short, the overall resistance of the strand drops, and in accordance with Ohms law, the current in the strand increases. This in turn means that the likelihood of another bulb failing increases, and so on until either a bulb fails open or the whole strand is toast.