[time-nuts] GPS 18x death and resurrection - was: GPS Week 1536 causing problems?

Kasper Pedersen time-nuts at kasperkp.dk
Sun Jul 5 21:45:15 UTC 2009


Hal Murray wrote:
> I don't think it has a battery inside.  That seems like a poor design.  Too 
> many reasonable use cases would include sitting in a drawer for extended 
> periods of time.
>   
There is a battery inside. A tiny little Panasonic rechargeable lithium 
cell. Mine were at 2.7V.
> Mine was less than a year old.  It had been plugged in and working fine for 
> several months.  Then it just died.
>   
Six months. The most recent component is dated 0751, so they've been in 
storage for a while before I got them.
> As I was poking around, double checking things to make sure I didn't inject 
> too much noise into this discussion, it started working again.
>   
I discharged the batteries on my pair. 0.6V was not low enough, then I 
tried again with a dead short for a few minutes, and they both came 
alive again. So just discharging in the drawer for a month or two might 
bring it back to life.
So I support the 'yet another buggy firmware' theory. MediaTek.tw does 
not give me a warm fuzzy feeling.
> In case it dies again... Does anybody know how to take one of them apart?  
>   
The case is two cups. The top has two 'rings' 2mm apart, the outer ring 
being the outside of the top. The bottom also has two rings, 1mm smaller 
than the top. The cavity between the two rings on the bottom is filled 
with silicone before the top is pushed on. It is held in place with 3 
snap locks, one of which is right next to the thickest bulge on the 
strain relief. If you insert a flat screwdriver and pry the top up 
exactly opposite that bulge, you can get the silicone to release and 
it's then relatively easy to see where the snaps are. Apply force.
If you have compressed air, pull off the bottom label, pull the green 
seal off the breather hole, and apply compressed air.
The magnets are glued on from the inside, there's nothing on the outside.

(and on a side note, the tiny little TCXOs in them are both ~1.4 ppm low)

/Kasper Pedersen



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