The machines are very fragile and don't like being manhandled at all
Would probably have to continuity check the whole RAM circuit out...
But while pressing the reset, just press down on various places on the board as sometimes a bit of pressure in the right place can temporarily "heal" a bad solder joint somewhere ..
Connected the Diagnostics Cart using Sidecart to the PC. It immediately identified U27 to be faulty. Confirmed with 41256 tester. New chip in and GEM appeared!
Thanks all for your excellent advice.
Amazingly the extra RAM which I butchered in all those years ago is still working fine. It was the original installed RAM. Amazing how just 1 chip can just fail.
chakobsa wrote: Tue Jul 22, 2025 4:03 pm
Bit of an update.....
Connected the Diagnostics Cart using Sidecart to the PC. It immediately identified U27 to be faulty. Confirmed with 41256 tester. New chip in and GEM appeared!
Thanks all for your excellent advice.
Amazingly the extra RAM which I butchered in all those years ago is still working fine. It was the original installed RAM. Amazing how just 1 chip can just fail.
Good stuff
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
