I’ve been looking out for the date version of the 0840 Cosmotron since I hadn’t previously found an example – designated the 4840, models with this movement were launched in 1970 and run at 21,600 beats per hour. Since my funds were limited, I took a punt on a ‘junk’ model on Yahoo Japan, especially because it has the date window at the more unusual 6 o’clock position. Described as not working, even after a battery change, it also had a damaged crystal. After checking that a new crystal was still available, and knowing that I could get it looked at at a later date by Paul at ‘Electric Watches’ I nabbed it, the only bidder, at just ¥1,800 – about £10 ($15). So not a huge loss if it were to prove beyond rescue. On arrival I could see that the dial and hands were in good condition – the hands are an unusual ‘see through’ frame design:
The cracked glass and wear to the case show it has been well used – the case also shows evidence of an original brushed finish. But the dial and hands are nice:
I have found before that it is always worth trying a new battery even when a seller has already tried one. Here’s a shot of the 12 jewel movement, which thankfully appeared to be in clean condition, with new battery installed:
And to my delight it fired up! 🙂 Not only did it start to run, but it also keeps good time, and the date change works just fine. So this was turning into a bargain – and a new acrylic crystal made specifically for this model was soon ordered, again at little cost. The damage to the old crystal is even more obvious with the movement removed:
There’s no guarantee that crystals are still available, but Sternkreuz still stock one for this model:
This is a compression fit crystal, and fits directly into the case without a bezel. I’ve not fitted one like this before, so the ‘crack’ as the press located it in place was a bit unnerving! But all was well:
I cleaned and very lightly polished the case to revive it a little, and after re-installing the movement, here’s the result:
The case back is good condition, and shows a production date of April 1970:
So, the gamble in buying a ‘junk’ watch has paid off – always a nice feeling 🙂
Sweephand's Vintage Citizen Watch Blog 
Greetings Stephen, I enjoy your Watch Blog. I am a keen collector of Citizen and Seiko higher end watches. I thought you might be interested to see what I just bought on Ebay. It is an Electronic Chrono Master , and I attach a link which should take you to my purchase page. regards, Stephen Loomes, Australia http://www.ebay.com.au/itm/191412140352?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
Hi Stephen, thanks for your comments. Congratulations on buying the Chrono Master, it is one of my favourites 🙂 I don’t know if you’ve seen my post on this model: https://sweep-hand.org/2011/07/11/this-weeks-featured-watch-10-the-electric-watch/
These originally came either on a mesh bracelet or a black leather strap if you want to get it as original as possible:
Stephen
Nice!
In addition, I, too, like the orange sweep second hand. I really like some color in my watch dials(not too much as that is distracting), as color livens up the whole watch experience, sadly, lacking in most of today’s wrist watches.
Hi Mike – I agree, a dash of colour can really enhance the look of a watch 🙂
Stephen
Stephen, that really looks nice. I like the orange secondhand,It pops out nicely from otherwise simple back ground.Simple and beatifull!
Hi Mikko, I really like it too, been wearing it all week. Keeps good time and it gives a warm feeling to have a nice watch for only a little money!!
Stephen
Hi Stephen, I recently bought a 4-4800, with a fetching blue dial. Despite a few teething problems with a displaced battery contact and switch contact underneath, it now keeps decent time and is a striking watch with the contrasting hands.
Does the 4840 have a quickset date feature? I haven’t come across it when playing with it, or it could be broken.
Hi Simeon, I have a couple of 4840 Cosmotrors and they don’t have quickset dates. Stephen
Hi Stephen,
One more question if I may. My watch has been running well and I am thinking about about regulation. When testing the watch on my timegrapher app it’s gaining about 20 seconds dial up and 15 secs dial down so that’s quite good considering it’s unknown service status. The beat error is consistently 1.2ms.
Can I adjust the beat error in the conventional way by adjusting the stud carrier? I assume that I am still looking for as close to zero as possible and certainly less than 1.0ms?
Hi Simeon, apologies for a later reply. The answer is yes, adjustment is possible by carefully moving the stud carrier, and good accuracy can be obtained.