Casio VDB-1000/VDB-100 "Open" repair

Finally working again after 3 years of saying "OPEN"

Updated March 2019
Fixed my VDB-100 today. These watches (the VDB-100 and VDB-1000) were, in my opinion the pinnacle of Casio's innovation in the 80's and 90's. This model in particular has a touch screen and dot-matrix display and is more sophisticated than just about anything they've released before or since (android watches don't count as innovation!).  It's a bit of a long story, so if you just want to know how to fix the "OPEN" message, then skip to the last picture in this article.

About 3 years ago I changed the battery and when I reassembled the watch it perpetually had "OPEN" printed to the screen. When this happens none of the functions work and the touchscreen is unresponsive. The watch is on but effectively useless.

VDB-100 rendered useless because it "senses" the back cover is still open.

As popular as these old watches are, it amazes me there aren't better resources about them online. I couldn't find anyone who had a clue what was wrong with it outside of the usual "You probably lost one of the tiny springs when you took the back off" (Which I didn't - not even remotely possibly - I opened the watch inside a plastic freezer bag so anything that tried to pop or fall out would be captured. Yeah, no lost springs.)

I spent a couple of hours over the next couple of days playing with the springs, trying to clean stuff (how it could be dirty was beyond me but I was desperate). Operating on the assumption that the open check mechanism might be checking current through the metal watch back, I connected wires trying to simulate electrical contact, but nothing made any difference. So I shoved the watch in a box and tried not to think about it for about 6 months.

After that I started looking at buying a replacement from eBay, but these things are insanely expensive. Even the ones in really bad cosmetic condition with scratches and the print completely worn off go for an average of about $130, and in good condition for about $200, and then there are the people whom I can't take seriously who routinely list them for between $500 and $1200.

I knew this thing was about 20 years beyond warranty when I bought it, but I figured I didn't have anything to lose so I called up Casio's officially designated repair shop for my hemisphere - a company in California called "The Time Machine". They were helpful, polite and realistic - they said I could send it in and they'd see what they could do but they didn't really have parts or expertise for stuff that old. About three days after shipping it to them I got a phone call saying that they couldn't fix it and that I needed to pay them $10 for return shipping. The problem, they said, was that there was a piece missing "probably lost when the watch was disassembled". That didn't make sense because the piece would have had to have been missing since before I bought it, and the watch was working fine until the battery went low. Now, in their defense, Casio Data Banks do normally have a white plastic frame that sits over the back of the watch that you need to remove in order to swap the battery. These particular models did not but they evidently didn't have a proper service manual to tell them that, and it didn't help the confusion that the battery change instructions printed on the inside of the back plate generically mention a "white cover".

Update: evidently I owe The Time Machine an apology - though I've seen at least two VDB-100's with no "white cover", I recently bought a junk VDB-100 because I wanted to get an original watchband and lo and behold when I removed the back, there was indeed a white plastic piece that pushes that button in when placed over the back. Only two possibilities occur to me, 1: one of the previous owners of my watch must have snatched or misplaced this part before it came into my possession, or 2: Casio used a cheaper means to press that door switch in (I can't really explain the extraneous spring that was found in my watch when I originally opened it).

The elusive "lost" white cover for the VDB-100/1000.  The peg on the underside circled in red presses the door switch when the watch is reassembled.

So I paid my $10 and the watch sat unopened in its return shipping box for the last two years.

This morning I checked the prices for these things on eBay and decided it was worth it to have another go at fixing it myself.

Things started pretty much the same way as the first time - checking electrical connections - this time with a multimeter. There are three springs that contact the watch back - one unusually long one on the top above the battery, and two on the right. The two on the right are used to activate the watch "speaker" which is basically just a round metal disc glued to the watch backing. I didn't know what the function of the one above the battery was, but after testing it, it was not apparently to conduct electricity - the spring socket was surrounded by metal which very clearly contacted the metal bracket that supplied positive current from the battery.

Then I did something colossally stupid. I sprayed contact-cleaner into the back of the watch. I'll explain what I had to do to fix this later.

The next step was to remove the metal clip that connects to the positive battery surface. I was looking for some kind of door switch that would make contact when the watch was closed. I thought maybe this was the purpose of the little leg on the bottom of the metal clip just to the right of center. There were shiny copper spots just beneath it and replacing the watch back might just push it down onto those spots. After looking more closely, though, the copper beneath it was actually just a pair of resistors and not contact points after all.

The action of removing the screws from the frame allowed some of the still-wet contact cleaner to get between the elastrometric/zebra connectors and the pads on the PCB so the LCD started showing missing lines and display errors. (I only figured this out a little later).

But, after the metal clip was replaced, instead of just saying "OPEN", for a moment the screen flashed "CHECK" then "BATT" and went back to "OPEN". Progress!!! Something I did made a difference. A little more poking around finally gave me the answer.

Circled: the not-at-all-obvious door switch on the VDB-100/VDB-1000.  If this "button" is not pressed in, the watch will perpetually show "OPEN" and not respond to touch controls.

So, see that circle area above the battery? When I first disassembled the watch, I found it a really long spring sticking out of the center of it (pictured below) that would be easy to mistake for the coil springs used to complete a circuit, but that's not what it's for. It may have been intended as part "door switch" mechanism, but after having found another VDB-100 with the white cover I'm no longer sure my watch wasn't just "rigged". In any event, that whole metal "circle" underneath that hole in the clip is actually a door switch. I took the spring out, and pressed a toothpick gently into the opening and the whole plate pushed down like a button. Sure enough when I turned the watch over, I could watch it go from "OPEN" to "CHECK" to "BATT". I popped in a new battery and up came the time.

VDB-100 found with a spring in the center of the door switch button.  I don't know what purpose the spring serves as I was never able to get it to operate the door mechanism - it would not seem to press the "button" down to tell the watch the cover was closed.

If you're in the boat I was and don't have a white plastic frame to push that button in, you can get your watch working normally again by finding something to stick under the plate to keep that button pressed down so the watch stops believing that the back cover is open.

The "door button" rigged with the ball from a sewing pin. I chose this part because it is hard, non-conductive and won't deteriorate.  Also, the little bit of pin on the bottom fits into the hole in the center of the button and keeps it from rolling off as I close the back.

Now about that colossally stupid thing I did by spraying contact cleaner into the back of the watch. Hopefully no one else will be dumb enough to do something like that, but if you have or if water has gotten into the works and caused a similar problem, you may be able to fix it the way I did. After removing the metal clip, then removing the remaining two screws in the upper and lower right corners, the back part of the watch works will loosen. DO NOT ATTEMPT TO REMOVE IT COMPLETELY. There is a tiny ribbon cable connecting the top of the PCB to the touchscreen. I don't know how to safely remove it, and I don't recommend trying.

With the back section of the works loose you can lift up the bottom edge of the watch to see the elastromeric/zebra connectors along the bottom and left. These are basically little strips of rubber with conductive channels that carry electrical current from the PCB to the LCD. I used a Q-tip and isopropyl alcohol to gently wipe the contacts on the PCB and the tops of the zebra connectors, then I used a hair dryer, being careful not to actually blow hot air into the back of the watch, but close enough to dry the air out next to it and evaporate any residue that might be left by the contact cleaner or the alcohol. Waited a good 5 minutes after this, and reassembled the watch. I count myself extremely fortunate that the LCD came back to life and is now fully functional - those zebra connectors are notoriously fiddly.