Do Synchronar's feel the cold.?

[Snetzka]

Well this little section of the site has been quiet for too long, so here's my contribution..

I am in the middle of repairing a couple of MK-1's and MK-II's in various states and currently i have under soak test a MK-II.
It has a new Xtal fitted (Round, cylindrical type) and a pair of new SMD Capacitors. I have it hooked up to a remote rechargeable battery to prove the solar cell / charging circuit etc. But recently it has taken to stopping overnight. Investigation is problematic because the very act of attaching an oscilloscope to it to diagnose the problem starts it running again, very annoying.!

The only thing i can think of is that it's sat in the window sill of my workshop / computer room, and over night the temperature drops sufficiently (>10'c) to stop the xtal from working.

I will of course move it from the window to a warmer part of the workshop and see if that solves the issue.

I was just wondering if anybody else noticed such things in watches etc...?

[clockace]

according to the spec page of the mkI/II booklet they should operate between -30C to + 50C. here in the states that is -22F to +122F. i have 2 modules that are acting just the opposite way. during normal wearing they work fine. if i get outside and they are in bright sun for more than 15-30 minutes they quit running. not just the display, they stop completely. once they cool down for a while, sometimes a half hr or so, sometimes more, they start up again. they are behind correct time so i know they have stopped running. can the cells get overcharged? i thought not. i think i am going to replace the cells in 1 of them and see if there is any difference. peter

[charger105]

I've had a few MkI and MkII modules that work fine for a while, and then stop. Normally if I fiddle around with them, they'll start up again, but stop again down the track sometime.

I've never attributed this to ambient temperature though. I've assumed it's an oscillator problem somewhere. I've changed QCs resistors and trimmers, cleaned all flux around the oscillator tracks, with no real improvement to prove this theory. My guess is it's a problem with the IC.

BTW Snetzka, how do you tell the value of the SMD caps since there's nothing written on them ?

Rgds,
Andrew.

[Snetzka]

Hi, Andrew.

There is a whole Synchronar thread devoted to the xtal oscillator and the capacitors... Each type (cut) of Xtal has a designed load (Capacitance) associated with it.. In my case a standard load of 12.5pf (Note - I use the small cylindrical (Watch) xtal's to replace the standard ones fitted.)

http://www.dwf.nu/viewtopic.php?t=2944

Yes, i have two modules like you describe, but in my case i am 90% sure it's a dry joint that i have missed - when i have the time i will go over every joint. The other assumption i have is that in these modules the oscillator is on it's limits of working and just simply needs a change of series resistor, load capacitor or indeed xtal to bring it back within the operational window. But that's a lot of trial and error, and reserved for when i have a bit more time..

And as for my temperature sensitive one, i brought it in from the cold and it has not stopped yet.. So i guess that will require a bit of experimenting with values to make it reliable, or try another crystal..

It keeps me of the streets..