Variable capacitor

[Seiko&Casio Lcd's]

Hi guys,
A question, what happens when the variable capacitor for adjusting the timing is defective ?
I am talking about an lcd watch, will it stop working or would there be some life in it ?
Any help would be much appreciated

[s_elias]

This just a guess - seems two are two conditions for going bad

A) the cap is shorted

I think it's in parallel to the crystal and would cause the oscillator to stop resulting in no display (no multiplexing) or a single digit nothing moving

B) the cap is open

I think things would work however the trimmer is off so time would run fast or slow

That's all based on what I've been reading

[Seiko&Casio Lcd's]

Thanks for the tips s_elias

[s_elias]

No worries,

I'm just a novice right now and still experimenting. I think I might have had it backwards after looking at a module last night.

Looks like one end of the trimmer cap goes to ground and the other goes into one end of the crystal. So that might mean it's in series with the crystal vs parallel.

If that's the case then the short on the cap would result in fast/slow time, an open on the cap would be a non-functional display most likely.

I did additional testing last night on good modules and bad / non-working modules and it seems to me the majority of the failures are either a bad crystal or leaking batteries eating away some of the traces.

I will have to search around and see if I can find some actual blueprints of modules to confirm.