IWC Pilot's story and tech info
I decided to write this article because I didn't find any solution to this problem on the net :) or maybe nobody has written about it yet.
Some time ago, I won an IWC Schaffhausen Pilot's ref. IW3741 in the online auction. This watch has a so-called mechaquartz (meca-quartz) movement. Calibre 630/1 was developed by Jaeger-leCoultre in 1987 (this movement was also used by IWC).
Mechaquartz is a hybrid movement - because it has a mechanical chronograph module. According to the description, the watch was "in working condition". When I got it, it turned out it works only partially - the chronograph module doesn't work 😡😤.
Diagnosis - Why it doesn't work?
I decided that I could handle repair "by myself", having this amount of saving in my pocket. I have some non-professional experience in watch servicing (hobby). I opened the case to look at the movement. It turned out that the chronograph magnetic coil connector was broken - actually, there was no connector inside! So, it couldn't work. There is no connection between the wire coil and the movement circuit board without this part. It also means that the chronograph wire coil is damaged. Somebody (a big watch seller with an excellent rating) didn't check chronograph functions or made a mistake in the item description.
Genuine parts issue
I started searching for the proper wire coil replacement for the Jaeger-leCoultre calibre 630/1 (631 contains a moonphase module). And guess what... there is ZERO available around the world - there was only something on the web archive that was SOLDOUT. After this disappointment, I decided to buy complete movement. It is not easy because the coil is often broken in so-called "for parts" offers. The price for an entire working movement is around the watch price.
Trying to adjust foreign parts.
So I decided to find an "alien" donor of parts, take out the donor's magnetic coil, adjust the coil handles and install it in the calibre 630. In theory, this could work. The calibre 630 chronograph motor doesn't require much induction power to rotate. If the coil fits inside, it will work. Like other quartz movements, this one contains a levet-type stepping motor (Wikipedia).
It turned out that it is pretty difficult to adjust/resize coil handles and not damage them.
A first donor circuit board with an integrated (size-similar) magnetic coil:
I had already attached the ends of the wire to the liquid silver (conductive adhesive). So, I created "connection points" directly on the coil surface. I used an eyeglass to be able to disconnect wire ends from the circuit board and move them to the liquid silver. Conductive adhesives are often used when soldering is not an option.
I made a small "reshape" of the left handle to fit the original IWC coil mounting. I also painted the coil to isolate wire:
The connection to the watch circuit board is made with liquid silver (conductive adhesive). This is not permanent - silver could be easily removed from the circuit board:
After putting all together, it was working! I recorded a short video with this great success:
Unfortunately, the joy did not last long.
... It was working, but only for about 3 hours ☹️ - after 3 hours chronograph started to slow down and finally, it stopped. There was a short circuit (in the coil). The donor coil was already pained I was not able to repair it. Even without paint, it is hard to fix a wire coil.
Then, I decided to try another donor:
But this one had developed a short circuit during installation and didn't work.
Making a watch magnetic coil
So after several attempts with different donors, I give up. After some hard thinking, I decided to use the donor coil differently - I need only a proper wire and an original coil core!
But how to wind wire (much thinner than a human hair) without 10k$ winder stuff?
I found a possible solution. Even a thin wire should be strong enough to survive the rewinding process. The strain on the wire causes the source coil to unwind. I browsed the net to the end and found a wire coil that is easy to un-wind (the coil without a protection layer on the surface) - Miyota GL20 or GL30 is a good match. I bought several for $2.5 each:
I don't have a professional winder, but I have an excellent Makita drill with smooth movement control, watchmaker mounting stuff (pin vise), and my re-winder PoC (proof of concept):
During rewinding, I used a paper towel as a tension balancer. The rewinding process takes (with pauses) about 25-40min (with a max of 2-3 turns per second). It is essential to be focused during the process - movements should be languid (from left to right coil edge) to create similar wire layers. It is tough to see wire after a while of rewinding (maybe a zoom screen would be a good option).
The first re-winded coil looks like this:
Nice ... but there was a short circuit with a coil core! I should have used better core isolation than acrylic paint. The mainplate is connected to the battery plus - so the coil will not work right.
In the following rewind process, I created a coil that didn't fit in the movement :(. I made too many wire layers.
The final working coil
In the final coil PoC (third), I didn't use rubber to connect wires because it was too big. I directly connected the coil wire and the output wire. I used glue to place the output isolated wire in the correct position. The output wire can be moved without damaging the silver connection point:
Final PoC - self-made wire coil parameters vs genuine part:
So, it doesn't look good on paper :). These are profound differences - the circuit board (chip) could be damaged. But I decided to install it - there's no other way and no sources of genuine parts...
Because there is no original connector attached to the wire coil, I have to use a new screw on the right part of the coil handle (the original screw is much longer and covers a connector and watch circuit board).
And finally, movement is in one piece:
It was a rather hope-driven development up to this point, without any serious calculations. I only estimated the number of required wire turns to create a coil. But it works. Video with working movement:
Summary
Updates:
List of tools used
Impressive and a lot of patience. I have one similar movement but the chronograph does not reset to zero.do you know how to adjust ?
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