Copal 701 + 705L: Hours do not switch reliably after the 59th minute.

[sakukas]

Hello

two of my Copal watches - a 701 and a 705L - are basically running well.

If I manually turn the minutes, the hour also falls after the 59th minute, as expected.

If the watch itself is running, the hour sometimes stops. However, this does not happen every full hour, but only maybe every three hours.

So far, so good.

If I then lightly tap the time setting button, the hour immediately jumps to the correct number.

I therefore do not think that there is a fundamental problem with the synchronicity between the minute and the hour.

I have had the watches running for about 72 hours now. It happens almost unpredictably.

Do you have any ideas?

Sascha

[Johan de Jong]

Sounds like a problem with the synchronization of the hours with the minutes. Here is how it should work:

1. the hour drops past the finger at the top of the tile around minute 50-55 but is still held back by the finger in between the minutes and the hours.
2. when minute 59 drops the finger between the minutes and the tiles moves to the right and releases the hour to drop as well.

If step 1 happens close to (or after) step 2 you get the unpredictable behavior you described. Please check thus when the hour passes the finger at the top of the tile.

Bit of background how this can happen:
The hours and the minutes may get out of sync due to wear of the tiles. Over time the fingers eat a little gap in the top of each tile (and the finger itself may wear a little too, but I think it is mainly wear of the tiles). This minute tiles wear faster than the hour tiles since they make 24 times more cycles. The increasing gap causes the minutes to drop ever earlier.

And how to correct it:
This is a fiddly business where the details depend on the exact mechanism. Basically you need to partially disassemble the mechanism until you can disconnect the gears that connect the hours and the minutes, and then rearrange them at a different position such that the hours first drop happens around minute 50-55. This is already difficult enough in itself, but in case the clock has an alarm (as both your clocks do) you also need to be careful to not bring that alarm out of sync. In my experience it can take a frustrating number of trial and error attempts to get it right.
Alternatively you could remove all minute tiles from the wheel and put them back in a new position. I have never done this and do not recommend it due to the risk of breaking a tile.

[sakukas]

Hi Johan de Jong
Thank you for your advice.

In fact, sometimes the hour falls into the holder / finger in the last seconds of the 59th minute. There is a "ping" sound that I don't notice on my other watches.
When this ping is heard, the hour falls correctly.

Although I am a perfectionist in most things, I think I can allow both watches this "peculiarity". I call it a "specific character" that the hour falls a few seconds late. I am fine with that.
There is a big risk that I will only cause major damage when taking it apart, and that would be a shame.

I will probably have to tackle the 702 because the lighting doesn't work. I think I need to replace the bulb here.

Best wishes!
Sascha