A7753 Service & Analysis - The thread you've been waiting for!

[14060 or 16610?]

My day job is pretty busy today, but I was able to spend my lunch hour tearing down the new A7753 movement. This recently released, much-hyped movement allows for the following:

* 3 - 6 - 9 subdial layout with running seconds at 9.
* no sunken datewheel.
* date adjusted by pushbutton located at 10:00.

My first impressions are that the A7753 is well-made. It can be reliable and keep good time for years and years with proper maintenance, not unlike the newest A7750s with which it shares the majority of its parts. Here are some fairly significant differences from its A7750 cousin:

* calendaring retaining plate, jumper, and spring.
* manual-set calendar driving pawl and gear.
* 3:00 subdial gearing.
* 2-position keyless works.

The movement I received was keeping good time. It was sent in for a full service and to repair a jammed datewheel which would not advance either in time-setting mode or via the pushbutton at 10:00. I noticed the mainspring did not "crunch" when reaching a full wind; evidently it was slipping on the barrel walls. This would obviously reduce the power reserve.

I also noticed that the movement was very dirty, with large chunks of dirt and various fibers (white and blue, mostly) found throughout. I even found a dried-up piece of lettuce or some other leaf. The keyless works were bone dry, though the stem and sliding/winding pinions were greased. None of the pivots had any oil on them (I checked thoroughly). The balance jewels *may* have been oiled, as they remained stuck to each other during removal. If you know A7750s, you know this is all very routine stuff.

I took many pics and will post back with more detail when I'm able. But I wanted the folks here to know a thorough teardown and analysis complete with pics is on its way.

Until next time...

G

 

[P4GTR]

Interesting. Sounds like its.. basically... an A7753. Not much difference between its Swiss counterpart, aside from QC?

 

[acharria]

Nice thread.. Tks..
Waiting for pics..

 

[R2D4]

@ P4, yeah aside from the lettuce, not much different. :rofl: Thanks for the news G.

 

[avenger007]

@ P4, yeah aside from the lettuce, not much different. :rofl: Thanks for the news G.

Um...you've got a little piece of......right.....um......never mind. You're good.

 

[Pix]

Thx for taking the time.
So basically we can rely on the A7753 if I understand. The problem might be spare parts ?

 

[COLDI]

Very eager to see pics and the full review! This is what I've been waiting for!

 

[rooster133]

Sounds great!
So basically all it needs is some vinaigrette and it's ready to go??

 

[14060 or 16610?]

Interesting. Sounds like its.. basically... an A7753. Not much difference between its Swiss counterpart, aside from QC?

Yes, essentially the same. But dimensions of some of the parts and especially the gearing for the counter at 3 are completely different from the gen 7753 parts. In short, certain spare parts for this movement will be difficult to come by, as the gen parts cannot be used. And since this movement is so new, the stockpile of spare parts is not as mature.

 

[14060 or 16610?]

If you've seen similar pics and know all about the non-A7753-specific parts, sorry. I'm posting them up anyway for folks who don't know what's involved in servicing these movements.

For starters, I removed the caseback. This caseback was already loose, so no need to use a wrench or 12-point die.

The first thing I noticed was that the date lever was stuck. I pushed it back out towards the case to free it up, and the date wheel was able to "settle" on a single date (it was previously jammed in between two dates). With this lever unjammed, I was able to observe the date changing by advancing the time. However, the quick-set date function via the button at 10:00 would not work. Each time the button was depressed, the date did not advance, and the lever would not return to resting position. This clearly pointed to lack of lubrication and a possible misalignment of parts.

Next I removed the hands, dial, and calendar retaining plate.

Here you get a better look at the components on the dial side. Note that the date wheel and the parts sitting inside of it are unique to the A7753 and, as far as I know, not interchangeable with the A7750 (the exception *might* be the date jumper). Notice the anti-jam date advancing gear.

Some more parts unique to the A7753. The intermediate gear is used to transfer motion from the 30-minute counter gear to the corresponding post in the tricompax configuration. Very similar in concept to the modifier plate in the tricompax-modified A7750s. Unfortunately, the extra play is still there, at least on this particular movement. The fit and finish of the gears is just not up to the standards of the gen ETA 7753. On a positive note, we get the lower positioning and resulting height, which eliminates the sunken datewheel. The date gear is used to advance the date wheel. It is actuated by a lever underneath the calendaring plate, which you will see next.

I removed the calendaring plate. Everything on the right side of the movement looks pretty familiar, nothing new here. But on the left notice the lever and spring. When actuated, the lever (more of a prawl EDIT: I mean "pawl") turns the date gear via the teeth on the underside (date gear flipped to show these teeth). Remember how the date was jammed when I received this watch? The lever was very stiff on its post and was difficult to actuate. I'm betting it's because the pivot and the spring (where it contacts the lever) were bone dry and causing too much friction. The date gear itself was also dry on its post, causing even more friction. Not hard to see why there were problems.

Notice this special spring which engages with the date gear. It is aligned by 2 posts and affixed with a screw screwed into a specially-drilled hole. This makes the calendaring plate also unique to the A7753. It’s rather ingenious how the Chinese took parts from the A7750 parts bin and modified them for this movement.

I disassembled further. Here are more parts unique to the A7753 movement.

The hour wheel had what appeared to be grease on it. But this “grease” had hardened into a hard, glue-like substance. I’ve seen this many times and even have a movement tray that was “etched” by it. It is difficult to remove manually, but is no match for the ultrasonic.

A closeup of the hardened glue on the hour wheel. Maybe the A7753 has more in common with the A7750 than I thought at first?

That’s it for the tricompax portion of the movement.

 

[acharria]

What a great review..
Thanks..
Now..I only need a better price on this...

 

[P4GTR]

This is the kind've stuff that reminds me what made visiting the boards exciting and interesting. Reminiscent of some of my favorite posts were ziggy's tear downs and tutorials. This is just as great, thanks for tearing it open for us all to see!

 

[Drulee]

Do you happen to have any ETA 7753 date wheels lying around? I was wondering if they are identical or not, from the pics Vac had posted it seemed that the teeth may be slightly different.

 

[14060 or 16610?]

Do you happen to have any ETA 7753 date wheels lying around? I was wondering if they are identical or not, from the pics Vac had posted it seemed that the teeth may be slightly different.

Unfortunately the 7750 and 7753 datewheels are different. I just confirmed via parts interchange lookup.

 

[rhack1]

is the thickness of the a7753 movement the same as the a7750 movement from the dial side to the stem?

just wondering if it could replace an a7750 movement - understanding that the a7753 would still need a pusher to advance the date - besides advancing the time round and round, that is...

 

[Drulee]

Unfortunately the 7750 and 7753 datewheels are different. I just confirmed via parts interchange lookup.

Not asking about the 7750 DW, but the ETA 7753 DW compared to the A7753 one. Or are you saying the A7753 is identical to the 7750 DW? Confused...

 

[babola]

I believe G is saying that the A7753 DW isn't compatible with either ETA7750 or ETA7753 DWs, or A7750 DW for that matter.

Just by looking at the photos it appears to me that the A7753 DW is somewhere in the middle between 7750 and 7753 DWs dimension wise. G, could we confirm this please?

thanks,
b

 

[jj69]

So it's safe to assume that this new "A7753" is not really a 7753 at all, but rather an A7750 with mods to make it work like a S7753?

 

[14060 or 16610?]

The rest of the teardown is pretty routine for an A775x movement. Lots of dirt and grit. This one in particular was littered with metal shavings all over the mainplate and inside the mainspring barrel. Absolutely terrible. I still don't see how folks leave these running unserviced from new. Even if it's running, it's just not right in my opinion. But of course that's a debate for another time. Your mileage may vary.

The reassembly is complete, and the movement is keeping very good time. However, I believe I have found a weak spot. It's no surprise. I'm still trying a few workarounds, but they don't look promising. I'll have more info, and a video, shortly...

is the thickness of the a7753 movement the same as the a7750 movement from the dial side to the stem?

just wondering if it could replace an a7750 movement - understanding that the a7753 would still need a pusher to advance the date - besides advancing the time round and round, that is...

The physical dimensions appear to be the same, so I believe it could be a direct drop-in replacement. However, your dial date window is not going to line up with the A7753 date wheel.

I believe G is saying that the A7753 DW isn't compatible with either ETA7750 or ETA7753 DWs, or A7750 DW for that matter.

Just by looking at the photos it appears to me that the A7753 DW is somewhere in the middle between 7750 and 7753 DWs dimension wise. G, could we confirm this please?

thanks,
b

Sorry for the confusion. Both the A7753 and A7750 datewheels are completely different from the gen ETA 7753 datewheel.

So it's safe to assume that this new "A7753" is not really a 7753 at all, but rather an A7750 with mods to make it work like a S7753?

Yes, that's essentially the case. The only thing accomplished with this new movement is fixing the sunken datewheel. But if you must have it, then you must.

 

[Drulee]

Great analysis, thanks for posting this.

I was wondering though why you keep the parts in the jars when using the ultrasonic. Wouldn't that restrict the flow (dampen the vibrations), thereby making the cleaning less effective?

The only thing accomplished with this new movement is fixing the sunken datewheel. But if you must have it, then you must.

The other thing they accomplished, unintentionally, is they now made all cases that use the movement ideally suited for a direct transplant of ETA7753/Dial without any mods