Saturday, June 18, 2011

Marathon JSAR Conversion

I have decided to compile the JSAR conversion into one post to make it easier to follow the conversion.

The original JSAR is fitted with the ISA 1198-103 movement. With this model, the conversion to fit the ETA 2824-2 is much easier as:

1. The movement is a direct swap, as both are 11.5 ligne. The metal ring (movement holder) that holds the movement in place in the case will fit both the ISA 1198 and ETA 2824. The dial feet are also in the same position.

2. The hands are a direct swap, except for the sweep seconds hand. The hand size on the ISA 1198: 90/150/20 (m/h/s), while the hand size on the ETA 2824 is 90/150/25 (m/h/s). So the sweep seconds hand needs to be broached to the correct size.

This is optional:

1. Swap the date wheel from black on white on the ETA to the new date wheel.

Other things we found out along the way:

1. Need to replace the standard length winding stem on the ETA 2824 to a longer winding stem due to the size of the watch case.

2. Instead of broaching the sweep second hand, you can change the mount post. This allows you to still use the sweep second hand if you decide that you don’t like the conversion.

3. The spacer between the movement and dial is not used. I suspect this is due to the height of the cannon pinion of the standard ETA 2824-2.

So with this in mind, I got the watch and the parts required for the conversion.

The watch.

The movement, ETA 2824-2 with the original black on white date wheel.

The new white on black date wheel.

The ISA 1198 movement inside the JSAR.

Another view.

Because the sweep seconds hand had to be broached, I decided to send the watch to my watch guy for the conversion.

Work in progress, the dial and hands fitted to the ETA 2824-2.

The old ISA 1198 movement. Note the white on black date wheel of the original.

The huge JSAR stainless steel case at 46.6 mm diameter, now with no movement.

My watch guy decided not to broach the sweep second hand, leaving it as a last choice. His reasoning is that the outer diameter of the sweep second tube is 0.27mm while the inside diameter is 0.20mm. If he were to broach the hand to 0.25mm (internal diameter), there will not be much metal left. His option was to change the sweep second hand mount post. I left the decision to him.

The location of the mount post.

He went with changing the mount post. The old mount post (0.25mm from the ETA).

He also had to change the winding stem to a longer winding stem as the standard winding stem that comes with the ETA 2824-2 was too short.

The old date wheel from the ETA2824-2.

Another unused part from the watch. This is the movement spacer between the the movement and the dial. I could have it installed but that would require the cannon pinion of the ETA to be taller. So it was decided that the spacer not be used.

The removed ISA 1198 movement. Remember to remove the battery if you intend to store the movement.

The new ETA 2824-2 movement fitted inside the case.

Another view of the ETA movement.

The case back. Note the crinkle washer. The washer holds the movement spacer in place. It does make the case back look like a compressor case back. The bad part is the washer is not held in place on the case back. This makes installing the case back a tad difficult.

The watch, now with an automatic movement fitted.


  1. I know this is kind of old, but do you know of any reputable place that I can get this done? I wouldnt mind doing this to my jsar.

  2. Hi Ryan,

    Welcome to the blog. Drop me an email.

    Best regards,