I now own a computer I've been wanting since the '80s for no reason other than it's as utterly cheap in price and quality as a fully functional home computer could get: A Timex Sinclair 1000. The picture quality is delightfully crappy. Unfortunately, half the keyboard doesn't work, which probably means its super-cheap ribbon cable kinked & broke.
ZX81/Timex Sinclair 1000 fault
@arielmt If you haven't solved it yet, it might also be worth checking the pull-up resistor SIL - *could* be some dry joints there.
(I built one from a kit, and, being a bunny of very little brain, didn't notice the polarity, so one keyboard column was dead until they fixed it, largely wiping out the saving in not buying it built =:)
ZX81/Timex Sinclair 1000 fault
@porsupah Oh, it's definitely the keyboard ribbon in both cases. They all but completely disintegrated in both ribbons at both bends.
I should probably give the boards a thorough once-over all the same. The video quality from one-meter RF cables is worse than a low-power TV station over 100 miles away.
ZX81/Timex Sinclair 1000 fault
@porsupah There's a UK auction site called SellMyRetro, and one of the sellers there makes and sells replacement keyboards. They're UK-specific, but the only thing Timex did different in the US version was some wording on top.
ZX81/Timex Sinclair 1000 fault
@porsupah Replacing the RF modulator? Yeah, some folks refined the composite mod to be pretty reliable, and some are selling assembled drop-ins that can fit into the RF box. (I'd like to keep the RF if I can, so yep, troubleshooting that is next.)
ZX81/Timex Sinclair 1000 fault
@arielmt Ouch! I suppose that was inevitable. ^_^; How feasible is replacing that?
Mm, I can imagine the modulator having degraded over time, unless you're maybe looking at hacking a composite output into it.