We’ve mentioned memory plague before, and a recent note in the
INMC newsletter
gives a more consistent cure. However, whilst looking
for the troubles with the Basic ROM with EPROMs in situ, a remarkably
naughty bit of tracking on the earth line of the EPROM block was
discovered. The earth track is connected to the ground plane close to
pin 12 of IC27, but nowhere else!!! So I now suggest when gridding the
back of the pcb that pin 12 of ICs 28, 29 and 30 be incorporated in the
grid thereby Incorporating the EPROM sockets firmly into the ground
plane. It can’t do any harm, and seems to do some good (but difficult
to prove).
By this time the back of the memory board is beginning to look
like the classic ‘rats nest’ with bits of wire and resistors hooked all
over it. Don’t worry, finding the cures, and incorporating the mods was
fun wasn’t it? And after all, the thing works reliably (or should
anyway).
