ZX Spectrum Projects – Diagnostic & Repair

November 1, 2019

Now I’m back on my retro computers I’ve put together this quick guide for those looking to diagnose and repair ZX Spectrum computers.

Schematics and Service Manuals:

Having a set of schematics or even better a full service manual is the good thing to have before starting any repair. Fortunately for us, full schematics and service manuals for the all ZX Spectrum models are available on the web. I have my Speccy schematics printed out on the biggest paper size I’ve got access to, namely A3. The service manuals are a great place to start when looking to diagnose a fault.

Schematics and Service manuals can be found at:

World of Spectrum

Spectrum for Everyone

IC Data sheets

wikipedia
7400 series
4000 series
Zilog Z80

Diagnostic Software Tools:

Happily the ZX Spectrum has quite a few diagnostic software tools to help the would be fixer in his fault diagnostics. Most of these are based on external ROM device which avoids the need to have a fully working Speccy or the problem of loading diagnostic software from tape.

Here’s a few ROM based diagnostic tools

Brendan Alford on github has “ZX Diagnostic”

Paul Farrow of fruitcake has the following ROM tools: 128K RAM Tester & ROM Tester
he also has the official Sinclair Test ROM as well
Phil Ruston of Retroleum has the following “ZX Spectrum Diagnostic ROM”

Tools needed:

Hand tools
Side cutters
Pliers
Screw Drivers: Philips and flat blade
IC extraction tool

Soldering Iron
De-soldering tool

Multimeter

Advanced
Oscilloscope
Power Supply (Adjustable/current limited)

Diagnostic software tools (see above)

TV Monitor/Screen (or car reversing monitor for composite video)

Repair mat
Anti static wrist or foot strap
IPA Wipes (no not the beer) – Isopropyl alcohol to clean edge connectors and contacts

Good web sites:

If the your own best efforts have not yet found the problem then there several good web sites that share their repair achievements where you can search. I like the following sites:

Dave Currah of Tynemouth Software

nightfallcrew

If you’re still no wiser, then try asking on one of the various Retro Computing Forums or general electronic forums in their repair section if they have one.

Remember to share as much information about the Speccy model, what it is not doing and what you have tried so far. Avoid simple statements like “Speccy not working please help”. It goes without saying that following the forums etiquette for posting will usually get you a more productive and polite response.

World of Spectrum forums
https://www.worldofspectrum.org/forums/

These are more general forums:
atariage forums

EEV Blog fourms