P2 displays single digit

[corona with lime]

I have a P2 which has begun to display a single random digit in a random location when power is applied. If power is removed and reapplied a new random digit appears in a different random location. Does this sound like a toasted logic module or perhaps just a bad timing chrystal?

[bruce wegmann]

Classic symptom of timing crystal failure. When I replace one of these, I clip the leads about midway between the crystal case and the circuit board, and trim the leads of the new crystal to barely touch the wires coming from the board. A tiny solder bead can then "bridge" the connection. I prefer not to disturb the solder connection at the curcuit board itself; they are fragile, and it is better not to heat surrounding components unnecessarily. Of course, ideally, the watch will need to be re-adjusted, since the new crystal will almost certainly oscillate at a slightly different frequency, and so affect the timekeeping accuracy.

[corona with lime]

Bruce - I've got a couple of modules with other ailments but good timing chrystals. Does it have to be a P2 style doner or can I pull one out of, say, a P4?

[bruce wegmann]

Ideally, a part should be replaced with an identical twin. If P4 modules are all that's available, I would certainly give it a try, as all Pulsar timing crystals are identical in design frequency [32.768KHz]. The only complication I can think of is that they be of different circuit capacitance, and the trimmer may not be able to fully compensate for that difference [which might result in poor timekeeping accuracy, but it would at least be working!]. You would need a timing monitor to be certain the crystal was operating at the correct frequency, in terms of seconds-per-month error.