Citizen 4520

[HectorLooi]

I'm currently working on a Citizen 4520 movement. This has to be the smallest and weirdest quartz movement I've ever worked on.

Firstly, it's small. Really small. Here's a picture of it next to a LR44 battery for comparison. 

And unlike conventional quartz movements, the construction of this movement is really weird.

The moment I took off the top plate, the rotor and 1st wheel are exposed. The PCB is right on the bottom plate. There are no dial side components and cover plates. Everything goes in from the rear.

Not sure if I'm able to fix this watch. The old battery leaked and there are battery juice crystals everywhere. And there is a 1 uA constant leakage current, which will drain the tiny battery in no time. But at least there's still a pulse and the rotor twitches.

[RichardHarris123]

I wonder what the theoretical size limit is for both a quartz and mechanical movement? 

[tomh207]

17 hours ago, RichardHarris123 said:

I wonder what the theoretical size limit is for both a quartz and mechanical movement? 

For mechanical I think the JLC 101 holds the record, I’m sure @nickelsilver has mentioned working on them. This is still the record for mechanical movements a hundred years after it was created.

 

Tom

[nickelsilver]

1 hour ago, tomh207 said:

For mechanical I think the JLC 101 holds the record, I’m sure @nickelsilver has mentioned working on them. This is still the record for mechanical movements a hundred years after it was created.

 

Tom

It seems the 101 is still the smallest- and yes, I've worked on a number of them, and their brother the 104 which is 2mm longer and 1mm wider. They are very nice movements, but get used in jewelry where they are squeezed in with tiny dials, not really practical for telling time. The Piaget 9P was the thinnest movement for some time, and is actually a really good runner, and much more legible at 20mm and round. The 101 is 14mm x 4.8mm rectangular.

 

There's been a lot of new efforts on the "thinnest" front in recent years. I personally hate them all (not the classic Piaget stuff), but impressive work. Surprisingly Bulgari has the record now.

 

I've never seen a Citizen 4520, man, that's small!