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Casio-F-91W die-shot

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Re: Casio-F-91W die-shot

#41

Post by hotpotamus »

vasqw wrote: post #12

I bought one of those recently and I was surprised by how inaccurate it was. It drifted like 15 seconds every month. From what I've been reading, that is normal, but I was surprised - with all the technological advances that we have it is odd to think that cheap timekeeping is not a solved problem yet! Also: how is the software of these watches without a CPU designed? Is it something like Verilog or whatever?

Citizen has a movement where they throw all the tech they have at it to guarantee 1 second per year accuracy. I remember things like quartz crystals have aging effects, so they used pre-aged crystals - little details like that. It even has an anti backlash mechanism on the second hand so that it ticks perfectly with no visible wobble. It probably doesn't make sense when it would be much cheaper to just use an external radio/GPS time source, but as a watch company, it makes a statement about their craft.

There are other high-accuracy watches (it's mostly a Japanese market thing), and I believe +/- 10 seconds a year is considered fairly pedestrian in that world.

Re: Casio-F-91W die-shot

#42

Post by jansan »

mmaunder wrote: post #24

I'm a big fan of the F105W which is basically the same watch with a vastly improved backlight that lights up the whole LCD. It makes a great watch extremely usable at night. I'd also recommend the Casio G-Shock GWM5610 which admittedly is about 5 times more expensive at $111 but it has UTC time and is absolutely bulletproof, along with radio sync and solar with solar charge indicator. It's currently my favorite among…

I had been wearing the F105W for about two decades and then decided that I want an upgrade. I tried to get as much value for my money and ended up buying the LCW-M100TSE-1AER from Casio's Lineage collection for 240€. Features are

- Titanium casing and strap

- sapphire crystal glass

- Wave ceptor (radio signal receiver)

- Solar cell

- Light (not great, but usable)

If Casio combined these features in a classic looking LCD watch that does not cost a fortune, I would not only buy one, but three of them. I know, there is the MRG-B5000D-1, but with a price tag of 3500€, which is more than then times the price of my watch with fewer features (no waveceptor) this is a bit expensive IMO.

Re: Casio-F-91W die-shot

#43

Post by [deleted] »

mmaunder wrote: post #24

I'm a big fan of the F105W which is basically the same watch with a vastly improved backlight that lights up the whole LCD. It makes a great watch extremely usable at night. I'd also recommend the Casio G-Shock GWM5610 which admittedly is about 5 times more expensive at $111 but it has UTC time and is absolutely bulletproof, along with radio sync and solar with solar charge indicator. It's currently my favorite among…

[deleted]

Re: Casio-F-91W die-shot

#44

Post by makomk »

kens wrote: post #38
addaon wrote: post #23

Earlier quoted context omitted.

This is outside my wheelhouse, but I assumed that the large capacitor area was a (trimmable) capacitor bank that could be put in parallel with the load capacitor on the (external) quartz oscillator, allowing calibration to counter some unit-to-unit variant in crystal frequency.

That's a possibility, but I don't see any laser-trimming marks on the big capacitor. Another option would be selecting capacitors with fuses, but I don't see any fuses or capacitors with powers-of-two sizing. With the complexity of the circuitry in the right hand side, I think there are a bunch of analog things going on.

The calibration for quartz crystal variance in these watches is done much, much later in the manufacturing process using solder bridges on the PCB - people have reverse engineered it. I think there are watch oscillator chips out there with one-time programmable calibration (particularly for analog watches) though.

Re: Casio-F-91W die-shot

#45

Post by einpoklum »

F-91W is the watch I wear today.

Actually, my favorite wristwatch - or rather the one I wore for 25 years or so - was a W-71. Unfortunately, you can't buy these except as vintage second-hand. I still don't understand why that is... I always felt it a more "aesthetically-balanced" version of the F-91W; plus it had 4 buttons rather than 3, which makes sense given the structure both watches. But I lost my W-71 while moving out of my last apartment, so... now I've had to settle on the F-91W. Ah well.

Re: Casio-F-91W die-shot

#46

Post by galangalalgol »

TedDoesntTalk wrote: post #27
mmaunder wrote: post #24

I'm a big fan of the F105W which is basically the same watch with a vastly improved backlight that lights up the whole LCD. It makes a great watch extremely usable at night. I'd also recommend the Casio G-Shock GWM5610 which admittedly is about 5 times more expensive at $111 but it has UTC time and is absolutely bulletproof, along with radio sync and solar with solar charge indicator. It's currently my favorite among…

> F105W which is basically the same watch with a vastly improved backlight Can’t stress this enough. The F-91W is useless at night because the backlight brightness is terrible. The F105W has an indiglo-style “EL” light that is very effective. The two watches are nearly identical from an aesthetic perspective. The functions are identical as are the buttons.

I've never had any problems with my f-91w at night. I can't use it as a reading light like the EL backlights, but it also doesn't ruin my night vision.

Re: Casio-F-91W die-shot

#48

Post by jimmyjazz14 »

mmaunder wrote: post #24

I'm a big fan of the F105W which is basically the same watch with a vastly improved backlight that lights up the whole LCD. It makes a great watch extremely usable at night. I'd also recommend the Casio G-Shock GWM5610 which admittedly is about 5 times more expensive at $111 but it has UTC time and is absolutely bulletproof, along with radio sync and solar with solar charge indicator. It's currently my favorite among…

I don't really understand your comment about avoiding Seiko (and yes as a Seiko collector I'm a bit triggered). In my experience Seiko makes absolutely great quality watches still with maybe the only issues generally being the occasional misaligned chapter ring though I pretty much only collect Seiko mechanical watches so maybe the situation is different with their quartz watches.

Citizen also makes some particularly interesting quartz watches the Chronomaster series (which is a Japanese domestic market exclusive) has one of the most reliable watch movements ever with a rating of +/-5 seconds a YEAR.

Re: Casio-F-91W die-shot

#49

Post by jimmyjazz14 »

vasqw wrote: post #12

I bought one of those recently and I was surprised by how inaccurate it was. It drifted like 15 seconds every month. From what I've been reading, that is normal, but I was surprised - with all the technological advances that we have it is odd to think that cheap timekeeping is not a solved problem yet! Also: how is the software of these watches without a CPU designed? Is it something like Verilog or whatever?

Citizen has a quartz movement that is rated to only drift plus or minus 5 seconds a YEAR which is quite impressive though they cost around 2000 dollars and are exclusive to the Japanese market. Several other brands out there make high accuracy quartz movements (which is done with thermal compensation) but they do generally cost more than cheap Casios.

Re: Casio-F-91W die-shot

#50

Post by [deleted] »

einpoklum wrote: post #45

F-91W is the watch I wear today. Actually, my favorite wristwatch - or rather the one I wore for 25 years or so - was a W-71. Unfortunately, you can't buy these except as vintage second-hand. I still don't understand why that is... I always felt it a more "aesthetically-balanced" version of the F-91W; plus it had 4 buttons rather than 3, which makes sense given the structure both watches. But I lost my W-71 while mov…

[deleted]
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