I got a really good deal on a used tacho and the 'small' clock for the 120y - so good that I didn't think to ask if they actually worked
After testing the clock I found it had a broken clockspring, burnt out coil and a stripped gear! These small clocks are so hard to find that spare parts are like rocking horse poo, a clockmaker would probably charge 5x more to repair it than its worth, and I really didn't want to fit one that didn't work. Sooo I pulled it apart, took some measurements, and came up with this:

A cheapo 1.5v ebay clock movement, cost ~$8.00


And a low voltage buck converter from aliexpress, cost a whopping $2.95


I cut the hanger bit off the top of the clock movement, drilled out the faceplate slightly, carefully reamed the hole in the hour hand to fit (the minute hand just happened to fit perfectly) and put it together -


The old mechanism v the new quartz movement (note - AA battery is just for testing!)


Soldered to the buck converter - I covered it with a bit of blue heatshrink -


Fitted in the original housing and tested with a 12v source -


Spruced up the needles with some fluro orange paint -


Final fit up - I did file a tiny notch either side of the minute stem so it would catch on the adjuster once the cover was fitted (too small to photograph with my crappy phone) -


Fitted in the Y (that old econometer is getting the boot next!) -


I thought the new clock movement might block more of the light from the old globe, so we popped in a nice led -


Pretty happy with the result. Dont forget to align the hands before fitting (line them up together at 12 o'clock), or you'll have to pull it back out to fix it - ask me how I know
Some of these clocks must be getting on to 50yrs old, I bet there's a few dead ones out there that could use a fix like this...
Now to test that tacho...

Oh -
I was concerned about the current draw from that chinesium buck converter, so I did test it while it was running on the bench power supply - my multimeter showed a tiny 750 microamp draw. Thats 0.75 milliamps - max acceptable current draw is around 50ma so it wont flatten the battery.

That's really cool, good work! I have a large collection of 200B SX clocks that also don't work, now I know that there is a simple solution

_________________
green200b - aka Alistair

The fleet:

Australia:
'80 200B GX - the green200b - hibernating
'81 RX-7 - 12A extend port - daily
'74 RX-2 - 13B bridgeport - cruiser

Europe:
'93 200SX - CA18DET - tourer

Nice work

_________________
http://goo.gl/3vkZ0i Cool Datsun T-Shirts

Couple of weeks later and the time is still spot on