CRG | ZX Spectrum - spares or repairs, let's fix it. Part 2. @CRG | Uploaded July 2022 | Updated October 2024, 4 hours ago.
Following on from last weeks video its time to dig into the ZX Spectrum and see if we can't get it fixed. By the end of part 1 we had it so the machine would at least turn on all be it the display was corrupted so will it be low ram, will it be upper ram, will it be logic or will it be all 3 and perhaps more...

ZX Spectrum Schematics - spectrumforeveryone.com/technical/zx-spectrum-pcb-schematics-layout

Z Spectrum Diagnostic Rom - github.com/brendanalford/zx-diagnostics/wiki

end theme - A Prehistoric Tale (1990) main theme by Jochen Hippel
CRG twitter - twitter.com/YT_CRG
CRG patreon - patreon.com/user?u=13919007&fan_landing=true

Chapters
00:00 Intro
00:18 Initial testing
04:21 Removed the Upper RAM
05:06 Removed the Lower RAM
07:07 Something's missing
12:20 Making a diagnostic ROM
18:58 Testing the diagnostic ROM
22:54 Where has the sound gone
26:00 The new lower RAM has arrived
27:48 Testing the lower RAM logic
31:06 Testing the upper RAM again
33:27 Who's a stupid boy then
34:42 Lets try that test again
36:18 ROM?
37:06 It works!
38:01 Conclusion and credits