Timefactors Precista PRS-10

This Timefactors PRS-10 came in with a stopped movement and a cracked crystal recently. These watches are based on the military-issue Precista G10 from the early 1980s and even carry the same name on the dial due to the fact Eddie Platts (the Timefactors proprietor) actually owns the trademark. I presume the movement had stopped due to water ingress as the insides were very mucky and there was a whacking great stretch of crystal missing around the circumference!

Timefactors Precista PRS-10

The reason I thought this worthy of featuring (besides the fact I’m a fan of the brand) is that the movement, a Ronda 715Li, isn’t readily available these days. However the Ronda 715 is and it’s a relatively straightforward job to swap the Li parts over from the old to the new movement. As can be seen the caseback features the model details, water resistance and the serial number.

Timefactors Precista PRS-10

With the back removed the large lithium battery can be seen, this is the ‘Li’ part of the movement and the battery lasts a lot longer (10 years I believe) than the 371 battery of the 715 movement. It looks like someone’s tried to force the battery down a bit further with a piece of packing to see if that would get it going. It didn’t!

Timefactors Precista PRS-10

Compare the battery with the standard movements one!

Timefactors Precista PRS-10

Once I’d taken the movement out the debris covering the dial could be seen, very dirty. It’s amazing the damage a cracked crystal can cause.

Timefactors Precista PRS-10

The dial and handset were removed ready for cleaning and the transplant. Apart from the rhodium plated movement of the original there’s no difference on the dial side.

Timefactors Precista PRS-10

On the other side, with the lithium battery removed, the differences can be seen.

Timefactors Precista PRS-10

The battery holder is the first thing to be removed from the dead movement, underneath they look a lot more similar now.

Timefactors Precista PRS-10

The circuits have to be stripped to allow removal of the batteries negative contacts as these also need swapping over.

Timefactors Precista PRS-10

Once the contacts are swapped the movements can be rebuilt.

Timefactors Precista PRS-10

And that’s it, we now have a dead Ronda 715 and a new fully functioning 715Li 🙂

Timefactors Precista PRS-10

The dial and hands were cleaned and refitted, getting that seconds hand to hit the markers takes me a few attempts usually!

Timefactors Precista PRS-10

The old crystal was pressed out and the case components were cleaned ready for the new one.

Timefactors Precista PRS-10

The new crystal and tension ring were fitted along with a new battery….

Timefactors Precista PRS-10

The seals were greased and the case closed up.

Timefactors Precista PRS-10

It certainly looks a lot healthier now, a shame these are now discontinued as they are a cracking grab and go quartz.

Timefactors Precista PRS-10

Timefactors Precista PRS-10

Timefactors Precista PRS-10

5 comments

  1. Hi, I’ve just restored one of these to health after the previous owner did their best to ruin it.

    I wouldn’t mind a new/spare crystal, have you got a record of which one you bought? Sternkreuz ATCR looks like a good candidate? Thanks.

    Like

    1. The coil and circuit are different part numbers but look absolutely identical to the naked eye. I’ve done this swap a number of times to resurrect dead 715Li movements and using the 715 coil and circuit certainly works and doesn’t appear to affect reliability. I haven’t had any report of the one’s I’ve repaired failing at any rate!

      Like

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