Re-capping a ZX81

[RetroMike]

I've just finished a re-capping frenzy on my Speccy and Amiga, and was considering it for the Issue 3 Zed, but wanted to ask whether there are any issues to be aware of when re-capping one. There aren't a great many caps on board, so if I have to buy some in, I might try & get radials, as I don't like the look of the axials when you've sheathed the +ve and turned it into a Z-shape to make 'em lie down. There's not much headroom in a Zed case, so I doubt I could put 'em upright?

[balford]

Unlike a Spectrum where a capacitor degradation or failure can have serious consequences for the voltage conversion circuitry and by inference the lower RAM IC's, there's nothing in a ZX81 that depends critically on the electrolytic caps.

The worst that can happen is that you might get some screen noise if the +5v filtering cap (C3) is degraded, or squiffy resets if C5 has suffered.

Best to inspect and replace only if they show signs of bulging or leakage.

B

[Moggy]

Agreed not really a critical thing even with the filter cap leaking pus all over the board the zeddy will still chug along quit nicely, never had one go down in thirty years of collecting and using the old door wedge. Certainly a lot hardier than its younger brother

[gozzo]

Personally I wouldn't bother 'recapping' a ZX81 or ZX80, unnecessary unless obvious failure....Spectrums, however are a different matter as the DC-DC converter circuit is a bit tetchy!

[balford]

Probably is worth stating, though, that a 16K RAM pack does contain the same 4116 RAM IC's as a Spectrum, and the necessary voltage conversion circuitry.

So it's probably worth recapping one of those if you're keen on keeping an original setup working.

B

[RetroMike]

I've done the Speccy, some of which were looking a little "iffy", and last night I even re-capped the old logic board out of my fridge freezer while I was replacing some blown components after it failed a few years back. Long story.

I've got three 16k RAM packs to my name, one being the Memotech one that I raided for the case for my ZXpand, and two that came with my two Zeds. Both original Sinclair, both in their polys, and one with a card outer. I'll probably sell the memotech and the least desirable Sinclair pack, keeping the Sinclair unit to go with my Issue 1 board that Charlie is currently playing with to see why it doesn't like the ZXpand. If I have some spare caps of the correct μF, I'll probably re-cap 'em all before I sell 'em, which might make them fractionally more desirable maybe?