7750 Issue

[HorologicalHobby]

I recently got done servicing my 7750 movement, and it has been giving me issues. The timeographer reading shows no issues, a little more positional variation than I'd like, but otherwise getting around +8 seconds a day. However, with the hands on, it seems to be loosing 5 minutes an hour, sporadically. I replaced the mainspring when I serviced it, I don't know if that's the issue, or what it could be. Could the canon pinion need tightening? Or should I do a complete tear down again and start over?

 

Any ideas are great help!

Thanks!

[HorologicalHobby]

It has occured to me that this could be a loose cannon pinion, and probably is, considering how smoothly the hands move. Any advice on how to tighten one properly on a staking set? Sadly I don't have a pin vise.

[clockboy]

If you have no cannon pinion tighter then I highly recommend this.

 

 

 

Although pricey it's versatile fitting all canon pinion sizes and the most important thing control.

I have some special anvils that fit to my Seitz jeweling tool which I use because of the control issue.

If you sneeze the cannon to much your in a host of trouble.

[Geo]

This is not a tool for use with the 7750. There is an indirect cannon pinion driver that has a slipping clutch, if this is slipping, I suspect it will have to be replaced. Here is a picture of it from Lawson's post.

[clockboy]

Good reminder Geo should have remembered this set up for the 7750. This is the part that also needs a good lube because if it is seized other problems happen

[Mark]

Agreed - the lube required for the correct friction is 9501

 

Do not tighten the floating canon pinion (the one under the hour wheel) - it is supposed to be loose.

[HorologicalHobby]

The floating canon pinion is loose, and I lubricated the offset canon pinion properly, and made sure it was not slipping on the post, however it is losing time like crazy, still. It is registering perfect on the timeographer, but is showing a few minutes lost an hour! I'm at my wit's end. This is the third complete teardown of this movement.  :pulling-hair-out:

[clockboy]

On the timeograher is it loosing 2mins an hour or is it only happening once cased up.

[HorologicalHobby]

It is perfect on the timeographer (+1 second to 5 positions), but once it has the dial and hands on it starts losing time badly.

[Geo]

This is a strange one. The symptoms certainly point to slippage, and the prime candidate would be the cannon pinion as previously mentioned.

You say that it was definitely not slipping on the post which is correct, but did you check for slippage between the triangular clutch plate and the outer gear? If that is also OK, it sounds like there must be something binding after the cannon pinion causing the pinion to slip because of the increased drive force required. If this was the case I would have expected that to show up as an issue on the timegrapher.

[clockboy]

I agree with Geo binding or slipping somewhere.

Example I had a Seiko that ran perfect on the timographer but when cased would not run after a lot of fiddling and many post here found that a previous repairer had fitted the wrong crystal & it was binding on the hands. Might be worth looking at these areas hands etc.

[Lawson]

Does it show the time lost on the timegrapher with the hands and dial on, and time properly with them off?

If so, the issue is not with the movement, it's in the fitting of those items.  Here's a few troubleshooting items to look at:

 

1. Check that the dial feet are not bent.  This can cause the dial to seat off-center and rub on either the pinion or the hands.
    Make sure each of the four holes in the dial are perfectly centered around each post for the hands.

2. Check that all hands clear the dial and the other hands ... especially the subsidiary seconds hand ( @ 9 o'clock) is not touching the dial.

3. Check the hands are not contacting the glass.

 

Hope this helps.

[HorologicalHobby]

Timeographer reading is perfect whether dial/hands are on or off. No sub seconds on this movement, however the hour and minute posts are slightly offcenter, not sure how to adjust a 7750 post to center them.

[clockboy]

If the posts are off centre then you might have a re-dial i.e. the dial is not the original & is not exactly the correct fit. If it is not binding on the hands and gives good readings on the Timographer in all positions when cased up I am to be honest at a loss. The fault is happening when the watch is being moved not static which would indicate a balance issue. When you change positions on the Timographer does it settle down quickly or does take awhile before it settles.

[HorologicalHobby]

Slightly off center, but the hands didnt seem to catch. All positions are good except dial down which added some beat error and -10 seconds.

[clockboy]

By any chance are the cap jewels in the correct way around i.e. the concave shape should face the balance staff. Just a thought.

[HorologicalHobby]

They are not. I'm going to just completely redo it. Maybe I missed a lubrication point...