Tuesday, 11 October 2011

ZX Spectrum +/48k - Composite Video Mod

I wasn't happy with the picture quality of the RF output from the spectrum. So I decided to do the composite video mod. Rather than just disconnecting the +5v line and routing the video signal directly to the RF output. I decided to remove the modulator circuit entirely. I also found on this website, that it is possible get a cleaner video signal by adding a 10-16v 100uF capacitor in series with the video line. Here's the pictures I took when I modded my Spectrum 48k+ to do composite. 

De-soldered the modulator from the spectrum board:

Removed the modulator circuit from the metal shielding/casing:

Added the 10v 100uF capacitor to the video output:

All soldered back on the the spectrum board:

Connected up ready for the initial test:

Works great and a much improved picture! I should of really took some before and after pictures:

The completed mod. Turbo loading from an mp3 player:

Heres's the orignial website for the composite mod:

And again a usefull website with lots of modding information:


  1. Sam, saw your blog, cool work. I am also into the ZX Spectrums, and wondered if you wanted to get in touch. I am just gonna start working on my speccies again soon, with a ZX Atasp interface for a cf card !!! Awesome stuff

    get in touch

    Matt Shaw
    Coventry (not far away !!!)

  2. Hey, Thanks Matt! Awesome. Bear in mind that i'm still pretty new to all the speccy stuff. There great systems to play with. I'm hoping to build a Spectrum portable or laptop later this year. Depending on time and funds! I'll allways be here if you have any other questions or comments to share!


  3. Brilliant. Not keen on taking the modulator out myself, as I like to leave as much original hardware in place as possible, but have harvested a 10v 100uF capacitor from an old pc motherboard which I have put into my composite mod, and routed around the original circuit. It would appear that the higher the voltage cap you use, the softer the image becomes.

    My 48k is a restoration project, and I don't think anyone will ever need the RF back but they could easily revert back should they wish.

    Thanks for the mod post and the great pics.


  4. Thanks for this, I used a 50v capacitor and it works great. Clean image quality although I would have wanted to place the capacitor inside the RF box. I didn't dare to apply force to the motherboard to get the RF circuit out... see my mod here: http://t.co/jvRF4bNpgb

  5. The orig site referred to in the first paragraph was saved by the way-back machine here http://web.archive.org/web/20130213213731/http://user.tninet.se/~vjz762w/rebuild.html
    good job.

  6. Pour Zx Spectrum ou son émulateur
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  7. Hi,

    I did the composite mod without taking out the RF modulator. It works pretty good on my LCD screen but the only issue I have are some colors which tends to bleed and shake. What this can be?