Sinclair ZX80 / ZX81 / Z88 Forums

I'm using this slotted diag rom: http://blog.retroleum.co.uk/20170918/smart-card-v2/ I cannot access any menu test functions as the initial boot the diag rom auto tests the lower/upper ram. If any ram errors are detected then I cannot proceed any further. The ram faults are always 16K/48K spectrum (...

Another strange anomaly is that when I power off the spectrum and remove the diag interface, then power the spectrum back up, some of the screen contents from the diags are still on the screen even though the diags are not actually plugged in ? Seems the RAM is still holding the same contents after ...

Just performed some checks with a multimeter on the ROM and Z80 address lines and found a strange resistance reading on A0. All of the address lines have a resistance of 8.9Mohm with ref to GND apart from A0 which is reading 5.5Mohm. Not sure if this is normal for A0 to have quite a large difference...

I'm having a similar problem but with Smart Card V2 ROM Diagnostics v1.40. The RAM tests seem to be reporting bad ram for the 48K model and shows the IC numbers at fault for a 48K spectrum (IC6,IC9,IC18). I have a 128K +2 grey model similar to toastrack board and these have 16 RAM chips starting fro...

Moderator note: split from this topic “ zx Spectrum 128k +2 Grey Screen Issue. Help appreciated ”. How are you getting on with this boot issue and garbled screen ? I've got a very similar fault also with my grey +2 issue 3 board. Using Smart Card V2 diagnostic ROM the boot fails with both lower and...

How are you getting on with this boot issue and garbled screen ?

I've got a very similar fault also with my grey +2 issue 3 board.

Moderator note: topic split and the new posts moved to their own thread: ZX Spectrum +2 (Grey) issue 3 board problems