[time-nuts] Ashtech Z12 question.

[Peter Monta]

>
> Does the Z12 have an internal memory backup battery?


Yes, there are two lithium thionyl chloride cells, Tadiran TL-5104.  They
are 3.6 V primary cells, cylinders roughly AA in size, with spot-welded
axial leads.  That part is obsolete, but Digikey has an equivalent,
TL-5903/P, which worked fine for me.  They're easy enough to replace, but
the inside of the box is a little awkward, with multiple board levels,
screws, and hinges.  Clip the spent cells free of their leads to make the
desoldering a little easier and to reduce the risk of heating the cells
(the chemistry is hazardous).  There is also some foam double-sided tape
helping to hold the cells in place; will need to replace that as well.

The two cells are wired in a diode-OR, so a single cell will also work (for
half as long).  While I was waiting for the shipment, I used a single
lithium coin cell, 3.0 V, to tide the box over, which also worked fine.

Cheers,
Peter