exxos's Atari, Amiga & retro forum

So as I posted elsewhere that I'd received this little fella:


Although I have a Spectrum + and a +2, I really wanted the rubber keyed Spectrum 48K that I'd had in my younger years, so was pleased to find this one on evilbay.

A good burst of nostalgia from this one, since I spent a lot of time with my own Spectrum back in the day.

Although scruffy, a little TLC and the case has come up very nicely, apart from the obligatory couple of small dents to the aluminium top cover!


The mainboard is an issue 3, and showed no signs of rework on the bottom, and the top was clean and dust free:


You can see that the modulator top cover has been removed in preparation for a composite mod, which can be found here: Spectrum Composite Mod

Although super simple and requiring very little work, the results are great:


However, the keyboard is only partly functional because one of the membrane connectors has failed:


It's gone so close to the case that repairs are not really practical, so replacement it is, and I'll get one ordered today. Pretty normal scenario for the speccy.

I just use a 100uF capacitor for the composite mod. Completely reversable, quick and simple. Works with every monitor I've tried and capture devices and it isolated the ULA from any DC offset issues.

Disconnect the 5V braid, disconnect the composite wire from the motherboard, disconnect the wire from the centre of the photo socket. Wire the cap to the motherboard composite, feed wire through hole and solder to the centre pin on the phono socket. I can't remember which polarity it is though off hand.

Just try one of these in replacement of your old membrane:

https://www.ginger-electronic.com/en/re ... model-zx81

I had one for my my ZX Spectrum and it was really day and night compared to the original keyboard.

With the membrane, a pair of scissors should fix that enough to get a replacement from RWAP https://www.rwapsoftware.co.uk/membranes.html

stephen_usher wrote: 05 Sep 2023 11:48 I just use a 100uF capacitor for the composite mod. Completely reversable, quick and simple. Works with every monitor I've tried and capture devices and it isolated the ULA from any DC offset issues.

Disconnect the 5V braid, disconnect the composite wire from the motherboard, disconnect the wire from the centre of the photo socket. Wire the cap to the motherboard composite, feed wire through hole and solder to the centre pin on the phono socket. I can't remember which polarity it is though off hand.

Yeah, I was prepared to use a cap, but the pic was fine as it was, though the article I linked to does mention the cap too.

HigashiJun wrote: 05 Sep 2023 13:01 Just try one of these in replacement of your old membrane:

https://www.ginger-electronic.com/en/re ... model-zx81

I had one for my my ZX Spectrum and it was really day and night compared to the original keyboard.

I've got one ordered, hopefully here tomorrow.

stephen_usher wrote: 05 Sep 2023 13:35 With the membrane, a pair of scissors should fix that enough to get a replacement from RWAP https://www.rwapsoftware.co.uk/membranes.html

Not fixable with scissors I'm afraid, it's cracked at the end where it enters the case.

rubber_jonnie wrote: 05 Sep 2023 17:34

stephen_usher wrote: 05 Sep 2023 11:48 I just use a 100uF capacitor for the composite mod. Completely reversable, quick and simple. Works with every monitor I've tried and capture devices and it isolated the ULA from any DC offset issues.

Disconnect the 5V braid, disconnect the composite wire from the motherboard, disconnect the wire from the centre of the photo socket. Wire the cap to the motherboard composite, feed wire through hole and solder to the centre pin on the phono socket. I can't remember which polarity it is though off hand.

Yeah, I was prepared to use a cap, but the pic was fine as it was, though the article I linked to does mention the cap too.

The picture will be fine, until the DC offset kills the ULA! The cap is there to decouple the circuits electrically.

rubber_jonnie wrote: 05 Sep 2023 17:35 I've got one ordered, hopefully here tomorrow.

Good !

HigashiJun wrote: 05 Sep 2023 13:01 Just try one of these in replacement of your old membrane:

https://www.ginger-electronic.com/en/re ... model-zx81

I had one for my my ZX Spectrum and it was really day and night compared to the original keyboard.

Did you mean this one?
https://www.ginger-electronic.com/en/re ... 6k48k.html