Capacitor replacement

[msknight]

I've got an issue 3 with axial and an issue 1 with radials. They look OK despite their age.

Normal protocol is to replace the radials.

Grateful for insight into what to do please, before I just do, "the usual," and potentially regret it

[Moggy]

Never replaced one yet in 40 odd years never had one fail, I don't think they are too critical on a zeddy someone will clarify I'm sure .

[1024MAK]

None of the electrolytic capacitors (two or three depending on version) is critical. No need to renew. Unless your machine misbehaves, in other words, replace on failure.

Mark

[Paul]

The 1uF only needs replacing if you have a zeddy that needs more than a single try to start properly.

[msknight]

The conventional teaching says to replace before they fail, because once they do they've inevitably leaked all over the board and cause damage.

So I'm wondering why the advice to replace on failure... and what this means for small collections of zeddys that only get plugged in now and then?

This is getting interesting!

[Paul]

The ZX81 capacitor are not known to leak but they dry out.
They are unimportant so nothing breaks if they fail.

[Moggy]

The conventional teaching says to replace before they fail, because once they do they've inevitably leaked all over the board and cause damage.

So I'm wondering why the advice to replace on failure... and what this means for small collections of zeddys that only get plugged in now and then?

This is getting interesting!

Because in my long experience they just don't fail or leak. The zeddy is such a low power low spec device that "conventional" wisdom doesn't really apply unless it keeps one awake at night so try not to overthink things, re the 81 it's such a simple beast really.

For the record I have been a user since day one and at least two of mine are in use 7 days a week up to 8 hours a stretch one doing actual computing.
( Higher maths, Forth and/or encryption, sorry not a gamer ) the other playing jazz/funk or whatever albums in the background and duff caps are the last thing I worry about if at all.

But there's no harm done if you want to go down the replacement route.

[1024MAK]

The conventional teaching says to replace before they fail, because once they do they've inevitably leaked all over the board and cause damage.

That's because you've been reading about the capacitors produced during the "capacitor plague". As a result, the internet us absolutely full of misinformation about electrolytic capacitors...

> The "capacitor plague" was a period of time when an unsuitable electrolyte was used.

Older electrolytic capacitors produced during the time when Sinclair machines were produced normally don't suffer from leakage failures during normal operation. Their chemistry is far more stable. Although they are larger than later, more modern components.

Service centres and repair shops (not just Sinclair, but throughout most of the consumer electronics trade) only replaced failed electrolytic capacitors or sometimes electrolytic capacitors that were known to cause problems (such as being next to a hot heatsink or in used in very demanding applications such as switching PSUs). There was normally no 'routine' or preemptive replacement of them other than as described.

And the lifespan of electrolytic capacitors can vary enormously. When not used in a very demanding application, they can be 40 or 50 years old and still be working okay, is perfectly possible. Compare to a lifespan of 3 to 10 years for some from the years of the "capacitor plague".

Mark

[Lardo Boffin]

I had to replace a capacitor in an issue 3 that did not boot consistently. Thats 1 out of I don’t know how many!