Amateur Hour Watch Restoration

Where it’s from

This stopwatch was given to me to work on by the father of my friend. Paul (my friend’s father) said he bought the stopwatch in Hong Kong in 1971, which he used to time his runs after he bought some accompanying Adidas shoes.

After a brief Google, I think this is a Heuer 7700 movement. The movement pictured in that article matches the picture of an eBay listing of what looks to be the exact same stopwatch.

What it looked like

Overall, it seems in excellent condition. The crystal is nearly scratch free, and the dial seems mint. There is a central sweep second hand, which completes one full revolution every 30 seconds. There is a small sub-minute hand that runs to 15 minutes.

Paul indicated that there is an issue with the sweep-second hand stopping/stuttering at around the 18 second mark. I gave it a full wind, and didn’t observe that issue, but after letting the power run for most of a day, I can see that it indeed seems to stutter around 18 seconds, and the lower the power gets, the more often it stutters. I don’t know if this is simply an artifact of having low power, since I’m guessing stopwatches operate slightly differently from regular wrist/pocket watches.

Aside from the low power issues, on a full wind it seems to work perfectly. Interestingly, the reset button causes the hands to reset in the direction closest to zero: if the seconds are < 15, it returns to zero counter-clockwise, and vice versa if the seconds are > 15. Paul thinks that he may have injured the reset cam one day in an effort to figure out exactly where the switchover in reset functionality is.

While I’m guessing that the drive/gear train is similar to a watch, I’m a little leery/anxious about the start/stop and reset functions. On the bright side, it is at least not as small as a wrist watch, so I’m guessing it will be relatively easy to open and clean. There’s probably gonna be some interesting stuffs in there!

How I restored it

May 18, 2025

After opening it up, and giving it a little twist, I can see that the balance wheel has low amplitude, which is causing the escape wheel to “stutter”. I’m betting that the issue is just low power transmission. Hopefully cleaning it will improve things.

After poking around a bit, and taking some readings on the watch timing app, I’m getting more confident that it just needs some oil for better power transmission. The timing reading was really good, gaining maybe 3 seconds a day, with about a 200 degree amplitude. For something like this, I’d expect the amplitude to be a little bit higher, so I’m hoping an oiling will help things out.

May 24, 2025

I took it all apart, and manually cleaned stuff that looked dirty. When reassembling, I had some difficulties putting the pallet fork back in, and I may have accidentally damaged the bridge very near the hole for the pallet fork pin. However, after getting the pallet fork properly seated, it seemed to be OK. I didn’t see any damage on the pallet fork pin itself. (It’s possible that damage was there before, I didn’t look after disassembly).

After giving it a wind, the pallet fork didn’t really want to tick over on its own, so I oiled the pins on the train wheels. This seemed to help, but when I put the balance back in, it seemed to stop running after a bit, even with a full wind. So, I took out the balance wheel cap jewels and oiled them, and kind of overwound the mainspring a bit to get things moving, and it seems that the movement is about back to where it was before: near 0 seconds per day, with about 200 degree amplitude. Starting to think that the mainspring is the issue now.

Side note: I accidentally broke the crown wheel spring. I ordered one from a slightly sketchy looking site, we’ll see if it actually gets here (so sketchy that the confirmation order email landed in my spam folder).

May 24, 2025

After reassembling, I took another reading, and it seems to have very slightly improved to around 220 degrees amplitude. However, when I took a look at the balance in motion, I noticed that it didn’t look to be oscillating that much. I took a slow-mo video of the balance, and it looked to be about 160-170 degrees, to my eye. Then I looked up what the lift angle of the movement is, and I think it’s actually closer to 42 degrees [ref] (the app defaults to 52). Updating the lift angle to 42 degrees in the app gives a reading of about 170, which definitely seems more accurate. Unfortunately, this means the movement is much less healthy than I thought. I’m going to try and source a new mainspring to see if that helps.

Jul 20, 2025

I got the mainspring and replacement crown wheel spring awhile ago now, but life got in the way of working on this. I had actually put the new mainspring in the barrel a few days after the last entry, but I hadn’t gotten around to re-assembling. So, I went ahead and reassembled (including the crown wheel spring, which actually appears to be correctly engaging with the center post), and took another measurement. On a very low wind, it still seemed to be at about 170 degrees, but when I gave it a full wind, it jumped up to about 220 degrees. Much better, but still not the ideal 270. Now I have to decide if I want to try disassembling and cleaning… It had already looked pretty clean though, so I’m not sure if it would help. Decisions decisions…

Jul 21, 2025

I decided that 220 degrees amplitude was good enough. I readjusted the timing to be optimized for dial up, fully reassembled and closed it all up; calling it done! I did one last test on the power reserve, by giving it a full wind before going to bed. When I woke up in the morning, it had stopped, which made me a little nervous. However, when I opened up the case back, attempting to let the power out didn’t do anything, which tells me that it had successfully gone through its whole power cycle. The Emmy Watch listing indicates a power reserve of 20 hours.

Sep 6, 2025

I changed my mind, and decided that I want to try and get the movement at a higher amplitude. I disassembled the winding works + train of wheels last night, and polished the pins and pivots. We’ll see if polishing did anything, cross your fingers.

Well unfortunately, after giving the pins a polish, nothing has changed. At least it’s not worse! I’m going to do a longevity test to see how long one wind lasts without any motion-works in place. I gave it a full wind at 2pm, so according to the spec, it should last until tomorrow at noon-ish.

Well, after coming back from the Bay FC game (another loss!), it didn’t even last 10 hours, so I’m going to say there’s something wrong with the power transmission. I’ve looked very carefully at the pivots, and everything seems clean, so as my last resort I will run the train of wheels, the main plate, and the bridges through the ultrasonic.

Sep 7, 2025

Ran the train wheels, main plate, and bridges through the ultrasonic, and got to work on reassembling.

Sep 8, 2025

I finished reassembly, and… it’s basically the same as it was before. I at least figured out that I can actually adjust the beat error though, and got the beat error down to about 0.2ms (it was about 1.5ms before). The accuracy app was having a difficult time reading the amplitude, but I took a slow motion video and saw about 215 degrees. So, I think getting it any higher is currently beyond my skills, unfortunately.

So to recap: when I received the movement, I saw about 170 degrees amplitude, but with an otherwise very healthy reading. Through the course of disassembling and reassembling the movement several times, I cleaned it, and replaced the mainspring (and replaced the crown wheel spring that I broke, oops). After all that work, it’s at 215 degrees amplitude, which is an improvement of about 45 degrees. I also adjusted the beat error down to 0.2ms.