🇬🇧 Sinclair ZX Spectrum: Part 3 (Refurbishing continues) [TCE

Work continues on refurbishing this Issue 2 Speccy in a Fuller FDS case. Unfortunately it seems I've encountered an issue with the Speccy now so more troubleshooting is required.
Ivan, a subscriber, very kindly donated one of his 128KByte RAM expansion boards so I am looking forward to trying that out - my first package from 🇷🇸 Serbia! In order for it to work you need to disable the upper 32KBytes of internal RAM, which I've done by adding a switch to inhibit the !CAS signal for that bank of RAM (make one OR gate input on IC23 always HIGH by connecting to +5V thus forcing the output HIGH, thus disabling !CAS).
I've verified the switch works by executing "PRINT PEEK 23732 + 256 * PEEK 23733" : I get 65535 (full 48KBytes), or 32767 (upper 32KBytes disabled).
However, after this it seems things started to go awry (nothing to do with Ivan's board).
I've added in various right-angled plugs for MIC/EAR and power, and replaced the original [RESET] button. I've also strengthened the keyboard cables.
I now have a vLA82 and a vLA1 - the vLA82 replaces the original ULA and also adds RGBS output (Harlequin or Spectrum +2 pinout apparently).
The vLA1 replaces the ULA in the ZX Interface 1 (not worried about that at the moment).
Link to Ivan's Github:
github.com/goloskokovic/zx16t...
That time I went to 🇦🇱 Albania (day trip via ferry from Corfu):
• 🇦🇱 Daytrip to Saranda,...
Replacement ULAs:
www.vretrodesign.com

[@MrWaalkman]

@27:12 it looks like you didn't get the solder to flow up the pins to coat the bottom as well as the top of the board. That may be it.

[@Brfff]

Hmmm ... good observation. I'll re-flow them. Otherwise, I had another look and can't see anything else that could be amiss ...

[@MrWaalkman]

@@Brfff I've had that bite a couple of times. Pain in the ass.