Date problems with old digital Casio

[Tom-HK]

My SP-400 (module 75) has just gone weird. It spends all its life in a watch box and has been performing flawlessly until now. Today I noticed that the date was wrong and when I tried to reset it I noticed that all but three of the months are missing and the dates from 1 to 31 exclude all days with the numbers 6, 7 or 8. Given the rarity of the watch / module, this obviously strikes me as a devastating development and I am hoping that someone can tell me it's not all bad news.

Has anyone got any ideas about what is going on or whether it can be fixed? I have emailed Casio for advice but the last time I questioned them about this watch they told me they had no records of it, so I don't expect them to be of much help this time.

[767Geoff]

I know, probably tried this but:

1) get a new cell.
2) remove old cell.
3) short the +ve to the -ve to ensure no remaining charge in system or let sit over night.
4) install new battery.
5) the battery cover has the letters AC and an arrow.
6) When the new battery is installed, short the AC battery cover to the point the arrow points to.

This should remove any confusion that the IC may have due to a static shock or low battery.

My HP01 had an absolutely bizarre display and I thought like you, OHOH but following the above procedure I resurrected it. I actually had to leave it without batteries for a few days too remove all residual charge in any of the capacitors.

Geoff

Is this the one?

http://www.haq.watch/Casio%20SP-400%20Gallery.html

Edited +ve and -ve (stupid autocorrect)

[Tom-HK]

Thanks Geoff. I haven't actually tried anything yet. Was hoping for advice before cracking the thing open. The particular watch to which you linked is the right model, but it is one that I sold some time ago. The one that is playing up is a shiny, NOS, practically unworn version. I had been dreading the possibility that something unfixable had happened to the circuitry (after an admittedly impressive 37 years of service), but now I have hope. I shall try the method you suggest and report results.

Thanks again!

[Tom-HK]

Well, it took me a while to get the new battery and to get around to installing it, but I have finally done it and the watch now works perfectly! Thanks again for the advice.

[Tom-HK]

More bad news, I'm afraid. Since my last report everything has been working perfectly. Right up until today. The date isn't the issue, now, but the time and the day of the week are

This isn't an expensive watch by any stretch of the imagination. Nor is it particularly fancy or high-tech. But it is incredibly hard to find and I was lucky beyond measure to have been able to pick one up in NOS condition, so this is pretty upsetting for me.

It can't be the battery after just a couple of months, so I will try shorting the thing again and see if that clears it up. Otherwise I may try speaking to Casio again.

[Tom-HK]

So, I removed the battery, shorted the movement, let it rest for a few days, shorted the movement again and replaced the battery. The problem has now changed in that different sets of numbers are missing but essentially the issue remains and I see no hope of recovery. Casio have voiced doubts about their ability to fix it but have asked me to send it to them. If I can muster sufficient willpower then I shall probably give the Service Centre a try, but I'm feeling a bit down about it all at the moment.