Today I received an IC tester through the post. Yay.

this is an important bit of kit for me. All I have to do is remove a chip from its socket, dorp it in the tester and press ENTER. This little gadget identifies and tests the chip in a fraction of a second. Crikey.

I’ve worked through the VDU and CPU boards and found one faulty 74LS393 counter on the VDO board and a 74LS00 NAND gate on the CPU board. Hopefully these are the source of my problems. If not, I’ll keep looking.

Supplies are on order. I’ll keep you posted.