A7753 Service & Analysis

[Guest 14060 or 16610?]

REPOST FROM RWI ORIGINAL THREAD: http://www.replica-watch.info/vb/showthrea...ouve-60596.html

 

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

 

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.

[mulder 0]

Thankyou for reposting this. Interesting reading

[AllergyDoc 42]

this was a great write-up (read it first on RWI)

 

I have a PAM with a 7753 coming. Hopefully it arrives sans a side salad.

[greg_r 107]

Great stuff - thanks for the repost!

[Silverspeed 10]

Great analysis....thanks for doing this, many were waiting for this

[KBH 7]

Reading this makes one realize the value of a good cleaning/service fairly soon after getting these Asian Chrono watches.

[dingle 62]

great read

 

 

The ant salad is popular nowadays....

[Guest 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.

 

 

Reassembly was also pretty routine and on par with that of the A7750. After all, most parts are shared.

 

 

Look at these excellent analyzer results:

 

 

Now for the weak spot of the movement - the quick set date function. Click on the video to see the incredible amount of play and wobble in the quick set gear which leads to jamming when the quick set lever is actuated.

 

[greg_r 107]

Again, really useful stuff. Many thanks!

[KBH 7]

Nice. Is there a fix for the quick set gear? Other than that problem it seems like a pretty decent movement.

[gB. 0]

Have you seen this issue with the quick set gear in every A7753 movement, or is this the first A7753 movement you've seen and it has this issue? Wondering if it's a systemic problem with the A7753 design, or if it's just an issue with the one you are working on. We all know there is wide variation in Chinese production from one watch to the next, and curious if that's also the case with the movements...

[GC 5,338]

Wonderful review of the new 7753 movt...

your talent and knowledge are inspiring!

 

thanks for share'n

[Guest 14060 or 16610?]

Thanks for the kind words, everyone. I am glad to help. Here are some measurements, for those of you wondering about A7750 swapability:

 

30.39 diameter

07.42 thickness (excludes rotor and post protrusion)

00.19 all 3 subdial posts

02.00 hour cannon

01.20 minute cannon

00.20 center chrono post

 

As for the issue with the quick set gear, I would truly hope it's isolated to just this specific movement. But I really haven't seen enough of these to be able to say one way or another. I haven't come up with a fix for it yet.

[nuker 30]

Does 7753 Asian clone interchangable with 7753 Valjux?

[twofake 0]

loved the thread. Thanks for posting all the photos and details. Great stuff.

[Thang 601]

Great post. Thanks for sharing.

[ahcho00 0]

had a question regarding this movement. i recently purchased a santos chronograph with the 7753 movement and at the 3 o'clock subdial the chronograph needle is loose. it sways left and right about a tick if i shake it.

 

is this normal? and if so, is there a way i can tighten the needle to stay in place?

 

Or did i get a defective one?

 

Thanks in advance.

[DR3M3L 6]

Though i ask myself the following question: he's doing a GREAT service and holding the movement in his fingers WITHOUT gloves.... WHYYYYY?!?!?! I can even see a fingerprint on the top left :(

[greg_r 107]

had a question regarding this movement. i recently purchased a santos chronograph with the 7753 movement and at the 3 o'clock subdial the chronograph needle is loose. it sways left and right about a tick if i shake it.

 

is this normal? and if so, is there a way i can tighten the needle to stay in place?

 

Or did i get a defective one?

 

Thanks in advance.

 

 

Depends on whether the movement itself is at fault or whether the hand is just a fraction loose on the pinion. The only way to find out is to get a watchsmith to look at it for you.