Omega Quartz LCD 1616 Circuitry Help

Canuck

Better pray to Saint Jude Thaddeus, patron saint of hopeless cases. He’s probably your only hope. Let us know if I’m wrong.

sheepdoll

I do not see any pix of the LCD side. How much corrosion was there around the chip and the display.

The old chips were fairly sensitive to static discharge. The nematic fluid can also leak over time. The polarization filters fade. This is basically a form or soap. (soap bubbles are liquid crystals.)

Some years ago I bought a bunch of bare glass displays. Most were for a stopwatch. Found a description how the multiplexing worked. As I recall there were several waves which had different phases. Was fairly easy to code an 8 bit AVR chip to make them work. Shortly after a version of the chip came out that had this function built in.

Since there are so many column drivers the chips are often what is called 'chip on die' or COD packages. where the chip is potted directly on the board.

An oscilloscope would be needed to check this to see if the system is at all functional. An old crystal earpiece can also be used to see if there is activity although the frequencies might be too high to hear. A pipe organ controller I am working on uses that for troubleshooting. I sometimes use these displays with the pipe organ stuff. Pipe organs also use shift registers to drive many columns of control lines.

Volt meters are only good for tracing DC power. Sometimes one can detect some RMS voltage from the clock lines if the frequency is high enough.

I also work with old cameras from the 1990s where LCD displays are standard. These usually have flex printed circuit which often fails. Especially where it bonds with the glass. I have experimented with the conductive paint as well as using the fiber laser to etch traces with less than satisfactory results.

When I fixed some Apple watches I learned about something called 'z tape,' which is conductive in the thin direction. I have too many projects, so have not actually tried it yet, although I did get some.

Would love to find a watch similar to this to experiment with. I have been collecting 134x parts which seem to have increased in popularity lately. Just having the Omega logo makes these attractive.

sheepdoll

You might get some activity with that old analog needle meter. If the quartz is good, then it will twitch the needle. The Quartz is the big oblong thing at the top of the last photograph. There might be some test points.

Good news is this does not use FPC to connect the display. I looked at the data sheet. I think the glass and the electronic modules are separate items.

In a lot of devices, like calculators, there is a rubber strip that is conductive in the Z direction. Sometimes the display is held in place by a hard plastic clip. It almost looks like this display is being held onto it by the corrosion. You might be correct that the display comes off. If this were my watch I would try prising it off with some hand levers. Not a lot of force needed, just enough to separate it from the conductive rubber risers.

One has to be careful of the reflective coating on the bottom. The front polarizer may also be removable. The data sheet shows these with separate part numbers.

I see quite a bit of de laminating of the FPC. So I suspect the electronics here are pretty much toast. Repairing them would require a hot air rework station and some decent soldering skills.

I did do a quick eBay search, not a lot came up in the US. Most of the listings were international. 9600 is always the ref number of the electronics module.

9801 is the display glass, so this does come apart. There are a number of listings for 1615, mostly in Canada. Not a lot can go wrong with the glass.

SG1993

Alright,
Got the screen off. This looks absolutely fried, right?

sheepdoll

Yes. There are thin vertical contacts embedded in the rubber strip.

Does not look to bad. COD is potted as I expected.

There are warnings in the manual (section 4.) about not cleaning in a bath. Dry cleaning only is specified. I think 'skin buff' is the same as chamois leather.

IPA comes in different grades. It can contain a lot of water in it. Denatured is a better choice. The main point of using an alcohol is to remove moisture.

My suspicion here is the battery gunk ate away at the components. I think dielectrics are mostly base caustics, so an acid like vinegar or lemon juice (citric acid.) is what I use to clean contacts and remove the gunk.

The contacts should clean up from where the rubber stuck to them. Use care when cleaning the glass side. There is a transparent conductive ink what connects to the plate traces.

As noted LCDs work by changing a phase across the crystal. This is done with a wave pattern which steps positive to negative. Usually there are three driver lines. This is usually created with a resistor divider. Easy to create with a micro controller.

Simplex displays have the other plate of the grid tied to each segment, which can operate individually. More common is to tie groups of segments together and turn them on really fast. Which is called multiplexing.

Once the drive lines are found, a second line can be used as a probe to locate the column indexes.

I thought I had this project on GitHub, might have been on another server. Should be on one of my backup drives. These days I use the full color 'smart' display screens. I did find the VFD clock project which emulates the popular display protocols on displays found on the front of audio equipment.

I also found a photograph of the breadboarded LCD tester.

This probably makes no sense as the control chip is off screen. It does however show the resistor divider for the row drivers. This is for a calculator display.

Calculators were so successful, that all the electronics manufactures used clocks and watches as the sequel. So successful the tech found its way into breakfast cereal giveaways.

I do have a seiko with dual analog/digital which I might look at again some time. Probably should put the LCD code up on the shared site.

Suspect your LCD is probably good. I think the frequency it too high to get any readings with the multimeter. One really needs a scope to see if any of the board is still good. Trimcaps are fairly standard and could be salvaged from a cheap movement. Of course as noted a rework station would be needed.