7750 (21,600 bps) running too fast!

[jj69]

I have a 3717 pilot's chrono with the Asian 7750 running at 21,600 bps (unfortunately). Whenever I wind it (about 20 turns) and set the time, it begins to run VERY fast. It seems to gain about 3-4 minutes in the first 15 minutes after it is wound.

After that, it seems to settle down a bit, but it continues too run fast.

I showed it to a local watchsmith. He put it on his timing machine and immediately said, "This thing is running a lot faster than 21,6!" He demagged it, but that didn't help. He even removed the balance wheel assembly to make absolutely sure the spring wasn't magnetized (it wasn't). He eventually said, "I've never seen anything like this." His best guess is that there's something seriously wrong with the mainspring. He suggested that it's possible they simply put the wrong mainspring in the movement when they assembled it.

Has anyone else ever seen this happen with the current version of the 21,6 7750 movement? Does anyone have any ideas?

I suppose I should start saving up for a Swiss 7750.

[ajoesmith]

The Asian 7750 slow beat 21,600 bph is famous for either running too slow or way too fast.

Its just in the assembly, no oil and lots of dirt etc in the movement. A complete strip down, cleaning and oiling will solve the problem.

Or you could get on the group buy for an ETA 7750, a good investment and money well spent

[magagne]

...Or you could get on the group buy for an ETA 7750, a good investment and money well spent

Don't bother paying for disassembling/cleaning/repairing a A7750 21k. The A7750 21k can be directly swap with a the Swiss 7750, no hands hole mod to do.