Hughes programable message watch with probs.

[digibloke]

I was having a button pressing session at the weekend to test for dead batteries/watches in my led collection and when I got to my message watch nothing happened when I pressed the time button. The message button was working fine so I checked for contact problems. Apparently nothing wrong there.

If I press the time button straight after the message has finished running the time comes on fine. If I keep on pressing it with intervals of less than two seconds it keeps on working. Any longer an interval than this and no dice. It's running ok and still keeping good time (and incidently, during setting mode the right hand pusher works just fine).

I've tried new silver oxides, a new case and swearing a lot but none of these helped.

Am I missing something obvious or has something microscopic gone belly up in the chip. Absolutely any suggestions would be greatly appreciated as I've run out of ideas.

[rewolf]

Very interesting behaviour...
It's obvious that there is no button contact or PCB trace problem because the chip recognizes the button in some modes, so IMO all that remains is a chip-internal problem, as you mentioned.

The time button can't set the "display on" flipflop, but other all other circuit parts can. But it DOES make its way to all other parts of the circuitry (setting, display timer retrigger).

[digibloke]

Hi Rewolf - I just checked it again and it's working. I won't be at all surprised if it starts playing up again though as these things rarely fix themselves. I guess it could be a temperature thing (the watch is very cold at the moment) or simply a lack of use but I think you're right about a problem with the time display switch in the chip. I'll wear it for a couple of days and see how it goes.

I've been wondering how long these things were expected to last at the time of their design? 30 years seems like pretty good going when you check out the complexity of the wire bonds.