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Discussion Starter · #1 ·
Since one of the members here asked for a review of the Shanghai B GMT movement found in an Alpha GMT and provided a watch, how could I refuse? (Thanks, Alpha-Getty)

Here is the watch, an Alpha GMT Master, no doubt you have seen one before:

Front



Back



Someone had used the wrong tool to remove the back and scratched it, and had done a rather inexpert job of reattaching the six o'clock hour marker. The crystal was uniformly dirty on the inside, but that isn't the reason for this post.

This is:



First thing we have to do after the movement assembly is removed from the case is remove the hands and dial. So, first we get all the hands together in one place and to pull them off at once:



Then undo the dial feet retention screws and remove the dial

Here is the dial side of the movement:



Some has been here before, one of the screws is missing. (red circle)

Removing the remaining screws, reveals the GMT or fourth hand complication:



The GMT complication is, perhaps, the simplest complication next to the day complication. All there has to be is a hand that makes one revolution every 24 hours. If the watch has a date complication, most of the gears are present, after all the date wheel indexing gear makes one revolution every 24 hours.

We can see that the date intermediate gear has a third gear mounted on top of it that engages in the 24 hour gear, simple.

But, how does the 24 hour hand get set? Well, in this particular example, it doesn't. Two gears are missing. In the next image, the two missing gears are ghosted in by red circles and it becomes a bit more apparent.



The smaller circle is constantly engaged with the date quick-change gear and the larger gear, the larger gear is allowed to float between the two positions indicated, controlled by the lever which is, in turn controlled by the crown. When the crown is in the intermediate position, the lever pushes the large gear into engagement with the 24 hour gear assembly and transmits the motion (clock-wise only) to the 24 hour wheel.



Here is a larger picture of the 24 hour wheel, we see that it is, in fact, two gears that have a friction clutch, so the the slipping gear (upper) can stay constantly engaged in the driving gear and the lower gear (attached to the hand) can be positioned as necessary.

Note the tolerance in the in the driving gear (the little one at 9:30), this backlash causes the hour hand to lag about 30 minutes after setting, because the little wheel has to catch-up to the gears (setting moves then out of contact). So when setting, advance the 24 hour hand approximately 30 minutes ahead of the correct hour, or it will appear than the 24 hour hand is 30 minutes slow.



Here is the bottom of the cover plate showing the spring that keeps the large adjusting gear out of the way during normal operation.

Now, some general shots that may, or may not, be of interest to anyone other than the owner of the watch:





During the service, in addition to the missing screw and gears, we found a nasty dent in the mainplate. While rather nasty in appearance, it does not affect the operation of the movement.

The crystal was very dirty, so bad it has to be removed to be cleaned.



Note: All those little bits of crud you see on the paper? Those are metal shaving than fell out when the bezel was popped off.



The bezel detent and its spring were in pretty poor shape, too:



Hands were in good shape, minor scratches around the fitting diameters but not noticeable, unless examined with a loupe, or you are looking for them.



Well, time to put it back together, the only thing I will note here is how to get the date to change at the right (12 midnight) time. First, the hour hand (in this case the 24 hour hand) is loosely fitted and the hand advanced until the date starts to change (this one advance half way before snapping over, true instant change date are a bit more fickle).



The hand is then removed and set back on so the date trips exactly at midnight:





Then the rest of the hands are installed. and the movement put back in its freashly cleaned case:



(Cleaning the crystal may have been a bad idea, now that six o'clock marker stands out like a sore thumb.)

The bezel was horribly loose on re-installation, so the retention spring was bent to give more friction. The 120 bi-directional click is almost imperceptable, due to the condition of the detent spring. I didn't replace the crystal gasket, so I would trust this beyond the 3 ATM on the back. I timed it to somewhere less than +15 s/d, but probably more than +7 s/d.

What do I think of the movement?

The Shanghai B is the most ETA-like of all the Chinese movement, (with the exception of the ETA clones/copies), it has an off-set center wheel and direct center seconds, so there is no possibility of a stuttering second hand, and much more reliable hack system. The auto winding is similar to the Eterna design, but uses the five jewel clutch in the reverser, making slightly less prone to spinning the rotor during winding if the oil gets gummy.

I believe that this is a slightly more expensive movement to manufacture, but not necessarialy more reliable than a well cared for ST16 or DG (or NN) 28.

These movements (the GMT models) have a stem height of 2.60 mm, so they are interchangeable with the ST16 and DG 28. This means that only one type of case need to be ordered if you wish to make both Sub clones or GMT clones, which is why, I believe these are commonly seen in GMT Master, and Explorer 2 copies.
 

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Another excellent tear down and tutorial Lysander :-!

The watch was full of surprises; missing gears, dent's in the main plate and all that mess with the bezel :-(

You should have seen the 6 o'clock marker before I cleaned it up...it looked like someone had glued it on while wearing wool mittens; there was grey fuzz stuck all over it. All I could do was carefully pluck off what I could. I also had to remove a huge glob of glue from around the marker as it had spread quite a bit as you saw.

Oh well, I didn't pay that much for it and the previous owner did say someone had been into it.
If I want a new movement, Mr Pink Pink will send me one for $25 shipped. Since the dial and bezel are kind of hooped, I don't hink it's worth spending any money on it.

The watch has provided more value to me and the rest of us in your capable hands. I had no idea how the GMT hand was driven but the pictures and your description make it so easy to see :-!

Thanks for giving us another detailed write up to add to the references :)
 

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Very nice lysanderxiii. Thanks for all of your work and effort to document it here. I am thankful you are a member and that you like to share your knowledge with us.

I'll link to the articles sub-forum soon.

Cheers,
gigfy
 

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Discussion Starter · #6 ·
With all the metal shavings and other stuff that was under the bezel, who knows what it originally was.

The detent (see picture above) may have had a small post on the conical shaped end, this would have engaged the ratchet machined on the lower side of the bezel, and made it unidirectional.

A GMT really should be bidirectional, though.
 

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A GMT really should be bidirectional, though.
... That is so logical, but I never thought about it like that. I always thought the bidirectional bezels were a sign of cheapness, that they were supposed to be uni.
 

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I am confused (sorry, sleepy, and read this too quickly),

I am under the assumption that this particular watch (dirty, messy, yuck etc.) did not come into your hands, Alpha-getty, direct from the manufacturers? But instead was purchased 2nd hand and previously tampered with, thus it's condition is not indicative of Alpha's watches when purchased new?

I am quite confident that it isn't, from all I've heard about alpha here, but I just want to be sure. (considering buying from them soon)

Also, if this particular watch is not a prime example of Alpha work, (which, as my slowly awakening mind leads me to believe that it isn't), what is the quality of a newly purchased alpha -- on the inside?

-Thanks,
SS


Thank you, lysanderxiii for this wonderful horological vivisection!
I am wanting to purchase an inexpensive GMT, and am considering the alpha 'for kicks' and it has been most helpful to know how exactly this specimen ticks :)P)

-SS
 

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I am confused (sorry, sleepy, and read this too quickly),

I am under the assumption that this particular watch (dirty, messy, yuck etc.) did not come into your hands, Alpha-getty, direct from the manufacturers? But instead was purchased 2nd hand and previously tampered with, thus it's condition is not indicative of Alpha's watches when purchased new?

I am quite confident that it isn't, from all I've heard about alpha here, but I just want to be sure. (considering buying from them soon)

Also, if this particular watch is not a prime example of Alpha work, (which, as my slowly awakening mind leads me to believe that it isn't), what is the quality of a newly purchased alpha -- on the inside?

-Thanks,
SS

Thank you, lysanderxiii for this wonderful horological vivisection!
I am wanting to purchase an inexpensive GMT, and am considering the alpha 'for kicks' and it has been most helpful to know how exactly this specimen ticks :)P)

-SS
Others may be able to testify with first hand experience, but in my reading about Alpha, the quality issues have improved over the last few years and I suspect that AG's watch is old enough to be from the time where there were a lot of complaints.

The other thing is that Alphas can become tinkering watches for those of us less experienced than lysander. So all that business with missing screws in the movement in the review above may not be the fault of Alpha. Its a lot easier taking a movement apart than putting it back together.
 

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I am confused (sorry, sleepy, and read this too quickly),

I am under the assumption that this particular watch (dirty, messy, yuck etc.) did not come into your hands, Alpha-getty, direct from the manufacturers? But instead was purchased 2nd hand and previously tampered with, thus it's condition is not indicative of Alpha's watches when purchased new?

I am quite confident that it isn't, from all I've heard about alpha here, but I just want to be sure. (considering buying from them soon)

Also, if this particular watch is not a prime example of Alpha work, (which, as my slowly awakening mind leads me to believe that it isn't), what is the quality of a newly purchased alpha -- on the inside?
Your are correct; this watch has had several owners since it left the factory.
The last owner only took it on trade then flipped it to me. Some time previous to the fellow I got it from, a hack was inside the watch as evidenced by the missing gears, missing screw and the nasty dent in the main bridge. The bezel click was also improperly installed at some point.

I'm fairly confident this watch is about 7 or 8 years old and was in good condition when it left the factory.
Poor assembly practices may have been the cause of the 6 o'clock marker coming loose but only a gorilla could make a mess of gluing it back on the way it was.

I've had three other Alphas; two with the ST16 and one with the Miyota. Al three of those are/were effectively new when I got them in trade(two even still had the plastic on the bracelets and case backs. Inside they were spotless and all are working wonderfully today. Theay are all at least three years old by now.

I am trying to decide whether to get another GMT(I am leaving this one with Lysander) or the orange bezel PO. Choices, choices :think:

Don't hesitate to grab an Alpha if one strikes your fancy, they are excellent watches for the price :-!

I don't say that because my handle seems like I'm biased but because I've been inside a couple of hundred watches now and I do recognize all of the good and not so good things that Lysander has pointed out for our education :)
 

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I am trying to decide whether to get another GMT(I am leaving this one with Lysander) or the orange bezel PO. Choices, choices :think:
You're kidding, right ? ;-) You don't really hesitate to get a GMT or an orange PO ?





GET BOTH !!! NOW !!! :-d :-d :-d
 

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Discussion Starter · #15 ·
Get the PO and put the GMT movement in it.
 

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Great job Lysander. Thanks for your review :-!

As a side note, when we (or I should say Bayram) pulled apart my GMT, there was dirt inside the movement. The watch was bought new by me, and it was one of the few watches I had not opened. So when Bayram did the disassembly, it was the first time the watch had been opened ...



You should never find dirt inside a brand new movement :-d

It was a watch I had bought about 5 years ago. I guess many here on the forum have said Alpha has gotten better since then, about using clean rooms? I certainly hope so ;-)

The GMT hand was also misaligned on mine, ... about 10 minutes off. The crown was very wobbly too. All in all, a real piece of crap :-d But for $37 I wasn't going to complain too much ... I just gave it to Bayram for the disassembly. The info gained (and the traffic it brought to my website) was well with the $37 investment :)
 
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