Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones...https://sinclairzxworld.com/
https://sinclairzxworld.com/viewtopic.php?f=7&t=2782
Andy Rea wrote: ↑Wed Feb 21, 2018 11:03 am In centre bottom dark thing just below and to the left of the diamond shaped chip... Regards Andy