Hughes module "under the hood", photos!

[rewolf]

What's under the black metal lid of a Huges module?
I opened one and pushed the camera to its limits (and beyond...):


The brain:


The oscillator chip, presumably it also contains part of the frequency diver.
The top right wire must be the clock signal, it is also routed to a test contact at the edge of the PCB where it is easily accessible even with the lid closed.


Then there are 2 load capacitor chips. They appear to be made of silicon and, very interesting, seem to have 4 different capacitors on one chip, presumably of ration 8:4:2:1.
Does anybody know if this was for factor level coarse trimming? Looking very close there appear to be wire residuals on all 4 capacitors per chip. Could it be that initally all 4 capacitors were wire-bonded, and later at the trimming stage the wires were removed according to the quartz' needs?


Belonging to the oscillator circuit, presumably the QC parallel resistor in the several MegOhm range (didn't think of measuring it).


4 digit driver transistors on one chip, and 8 segment drivers transistors on another (one of them unconnected):


Fianally the LED chips:


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[LEDluvr]

Fascinating pictures Rewolf.
I'm curious, was this a fully functional Hughes module or did you pull off the 'hood' of a non-runner?

[abem]

Very cool. It's interesting how the Hughes modules have a lot in common but little differences too. The module that I photographed has a similar layout but is different in a number of places.

I'd be curious to hear what you're using for a camera, lenses, lighting and exposure settings to capture these images.

-abe.

[rewolf]

I'm curious, was this a fully functional Hughes module or did you pull off the 'hood' of a non-runner?

The latter. Someone (not me) had already replaced the QC, but it still didn't work. It's not a contact problem. I'll give the QC another try after I saw the soldering...

I'd be curious to hear what you're using for a camera, lenses, lighting and exposure settings to capture these images.

Oh well, err, nothing special.
The photos were made on my dining table.
The lighting is the light hanging over my dining table (which is maybe a tad better/brighter than in an average household, over 2000lux on the table ).
For the photos where the chips throw "shadows" I side-lighted with a 700lm LED flashlight lying on the - you guessed it - dining table.
The camera is a Canon Powershot A640, several years old, it was the "company camera" at my workplace until the LCD broke. They bought a new camera, I took the broken one, got a replacement LCD screen for $16 off ebay, et voilà, my first own camera .
Exposure - I set it to ISO100, the camera does the rest. Sometimes I fix exposure time to 1/25 or 1/50 s to avoid interference with 100Hz flourescent lighting flicker.
And I don't have a tripod.

It's interesting how the Hughes modules have a lot in common but little differences too. The module that I photographed has a similar layout but is different in a number of places.

Yours appears to be a later version. Higher integration and better PCB quality (gold-plating).

[retroleds]

Very nice pictures - thank you Rewolf.

The lowly Hughes seems much more resilient than the vaunted Pulsar movements. Shame the displays weren't bigger and the crystal is an odd frequency. But a shortage of the crystals shouldn't be a problem if people remember to occasionally pull good crystals off Hughes movements with display, not timekeeping issues.

[Huertecilla]

I opened one and pushed the camera to its limits (and beyond...):

Thank you Wolfgang.

I had the ´The Digital Watch Repair Manual´ by Greg Zanoni with it to compare the text and illustrations with your text and photos.
Highly informative.

[rewolf]

The lowly Hughes seems much more resilient than the vaunted Pulsar movements. Shame the displays weren't bigger and the crystal is an odd frequency...

Err, is it not 32.768kHz (please forgive my ignorance)? That would explain why a new QC didn't help. The module is from a Wittnauer Polara, It'd be nice if I could get it working again. I have access to more Hughes modules, but either they don't work (don't oscillate), or they are in nice watch cases. Seems I'll have to take a working one and look at it with a scope.

I recently restored a friend's neglected LED watch collection (some 50 watches), about half of them just needed new batteries, most of the rest had only contact problems, and now 7 or 8 non-workers are left, the Wittnauer being one of them.
BTW: I documented the process photographically, that is, I have now photos of all the watches and their modules, and a "database" which watch had which module inside (though some of them could be non-original) I learnt a lot about LED watches in the past 3 weeks

I had the ´The Digital Watch Repair Manual´ by Greg Zanoni with it to compare the text and illustrations with your text and photos.
Highly informative.

Does the manual say anything specifically about this module? Escpecially about load capacitor trimming?


BTW: an old but very informative thread about Hughes modules: http://www.dwf.nu/viewtopic.php?t=2081

[Huertecilla]

Err, is it not 32.768kHz (please forgive my ignorance)? That would explain why a new QC didn't help.

786.432 Hz.
The divider has different logic too; divides first by 2 then by 3 and then 17 times by 2 again, so it would not get nearly at 1 with a 32K QC.

Does the manual say anything specifically about this module? Escpecially about load capacitor trimming?

It is generic only but does deal with load capacity trimming yes.
I suppose it will not teach you much but the manual is only $19,95
http://www.zantechinc.com/store/categor ... ategory=18[/quote]

[rewolf]

Err, is it not 32.768kHz (please forgive my ignorance)? That would explain why a new QC didn't help.

786.432 Hz.
The divider has different logic too; divides first by 2 then by 3 and then 17 times by 2 again, so it would not get nearly at 1 with a 32K QC.

Absolutely sure? The module I pictured above? ALL Hughes modules? I thought only some special early ones used the HF quartz.

[Huertecilla]

Err, is it not 32.768kHz (please forgive my ignorance)? That would explain why a new QC didn't help.

786.432 Hz.
The divider has different logic too; divides first by 2 then by 3 and then 17 times by 2 again, so it would not get nearly at 1 with a 32K QC.

Absolutely sure? The module I pictured above? ALL Hughes modules? I thought only some special early ones used the HF quartz.

Well, I do not know what I do not know but for as far as I know Hughes used 786KHz.

[retroleds]

All Hughes modules use the 786. Even the calcs and the dual LED/LCD. Which is why I suggested playing "Repo Man" on all crystals that seem to keep good time but the display or logic is otherwise kaput. I have a small jar full, if you need some.

[rewolf]

Damn. So that's it. Another thing learnt about LED watches...

Huertecilly wrote "The divider ... divides first by 2 then by 3 and then 17 times by 2 again" so after the 4th stage it is 32768 kHz and thus in all following stages "compatible" with a standard quartz.

Has anyone ever tried using a replacement oscillator? As can be seen in the pictures above, the clock signal is easily accessible. One could remove the wire to the oscillator chip and feed in a clock signal at the test point. The question is: at which point in the divider stage is this clock signal - I'll have to measure the clock signal's frequency. Or does anyone know?

[Huertecilla]

so after the 4th stage it is 32768 kHz and thus in all following stages "compatible" with a standard quartz.

Yes; if you swap the whole oscilator circuit by a 32K one, the rest of the module simply receives the ´1´ pulse so is oblivious to the QC and frequency dividing.

Seems simplest to put in a 786 QC though.

[rewolf]

....Seems simplest to put in a 786 QC though.

If you have one... in this collection are 11 watches with 6 or 7 types of hughes modules. 3 of them don't work though the modules are absolutely clean, no corrosion or any visible damage.

Back to my idea above: use an external oscillator and feed the signal directly to the main chip via the test point.
I took a working Hughes module that looks the same as the one pictured above (only the plastic is of differnt colour) and looked at signals at the 2 test points.
Result: the oscillator feeds 768Hz to the main chip, that is, it dicdes the crystal frequency of 786432Hz by 1024 (that is, 10 times by 2). At the other test point the main chip provides an 8Hz signal. So the divide-by-3 stage must be on the main chip.
Bottom line: there is no straightforward way to get the 768Hz for the main chip from a standard 32768Hz crystal.
Below are scope images of the two signals. Note that scope GND was connected to 1.5V for both images. Also note the different signal levels: apparently the oscillator chip runs only at 1.5V supplied by the "upper" battery (signal level L=1.5V, H=3.0V).



Updated annotated module photo:


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[Huertecilla]

Bottom line: there is no straightforward way to get the 768Hz for the main chip from a standard 32768Hz crystal.

Thanks for the illustrative explanation.

Drop Ed a line for a handfull of the things from his jar.