ZX Spectrum 128k toastrack horizontal bars at power up

[kbjunkie]

Hi 1024MAK

It's a plastic OTP ROM (Intel P27256) I think? (Could be a mask ROM I guess).

I've attached a pic.

Cheers again,

KbJ

[1024MAK]

Yeah, that’s definitely a OTP EPROM. Intel refers to it as a ‘production’ or ‘plastic’ part in their datasheet (attached).
It’s likely it’s starting to suffer from the memory contents degrading.

You could try reprogramming it. But that will only work if you use exactly the same file / data that it was originally programmed with. And it is possible to set your programmer to ignore the fact that it’s not ‘blank’. And your programmer either tries programming each memory location before checking it ‘programmed’ okay rather than reading and then deciding if each memory location needs programming. Or you can force it to program each memory location regardless. In other words, it needs a ‘dumb’ (slow) programming algorithm not a fast, intelligent or smart programming algorithm.

Then if successful. Try it in the machine again.

But obviously only do this if you find this kind of thing fun

Mark