Faulty Commodore *LCD*??? HELP!!!

[slystav]

Hi everyone,

Last hope rests with you so don't let me down! I just bought a Commodore watch, I think it's LCD but if you look very closely you can see lots of little circuits around the numbers.

Anyway, I bought it 'as seen' and of course it doesn't work when it arrives. I've just fitted a new Silver Oxide battery which is an equivalent to the one I found already in it when I opened it up. There was no obvious damage or leaking from the previous battery and its voltage measures around 0.9v instead of a nominal 1.5v so we can judge how long it's been in.

I fitted it back into the case (although a little confused which way round to position the plastic membrane as it has locating holes...?) and clipped the back on snugly and nothing. Took the back off again, played around with it and managed to get the backlight to light up although it's VERY dim from the front. I put a meter across some terminals on the PCB and am getting 1.5v OK so the battery's definitely in and the buttons seem OK too.
The basic problem is that from the front, when the watch is back together, everything's just black and the buttons don't do anything, except if you look VERY closely you can just see the bulb shine through around the PCB when you push the light button.
I don't have any test equipment apart from a basic multimeter to test voltage, resistance, current so can't check the crystal etc.

I don't have a picture of the PCB yet but there are three button terminals which correspond to 1) Time/Date/Alarm/Snooze 2) Set 3) Alarm.
The module is labelled "Commodore, Unadjusted, NO(0) JEWELS, MADE IN HONG KONG". There are two small springs on the PCB but I don't know what they are for. They appear to be soldered to +ve tracks. The case, I believe, is positive and the button terminals negative.

The PCB is permanently moulded into a plastic module housing which I would rather not tear off. The PCB is additionally labelled in etched copper with the C= Logo and "commodore" and a just-visible part number of sorts.

Just to clarify, I bought this as an LCD watch but when you look at the screen it is all black. Look closely and you can see seven segment displays with circuits but they are all dark, like gunmetal grey. I used to own watches like this and they were always light grey and the numbers were black so I'm a bit confused.

I paid around ?17GBP including the new battery which right now is about 25 USD and I'm not prepared to spend much more than that but I'd love to know for certain what's up, if it's broken and how to fix it. Also what it's worth and how common they are!

Hope you can help.

Thanks

slystav@hotmail.com[/img]

[retroleds]

Slystav -welcome!

The springs you mentioned generally need to make contact with the case(caseback) to complete the circuit. Most LCDs have an internal current path so the display will work without the case back on, but there are the odd ones where part of the path was OUT thru one spring and then Back thru the other(nutty, huh?)

The black screen doesn't sound good - generally that is a sign of leakage of air into the liquid crystal panel. The digits and "circuits" you are referring to is a conductive matrix that was printed onto the glass panel - when electricity excites the particular circuit path, the crystals in that path change color(I am oversimplifying for brevity).

Try running a jumper from one of the "springs" to each of the contacts that the buttons touch normally - if you get a display then the screen isn't shot(obviously you have already located the one for the backlight). A picture is never a waste here - if only for the edification of the larger forum group, which you are now a part of. :)

[slystav]

Hi,

Thanks for the advice. I see what you mean about the springs but the inside face of the watch back seems to be filled with a white disc of sorts which makes me think this is an insulator and one or both of the springs arent meant to contact the back for some reason. There is also a black flexible plastic disc with some cutouts which fell off the pcb when I took the back off, perhaps another insulator?

I'm a little worried about the LCD though as now you mention it is does have some light dots around it, perhaps bubbles? there is no visible damage such as cracks or chips but I thought it very unusual to be all black with these spots or cavities there. Can I do anything to rescue my watch? If I was that comitted I'd spend some money fixing it up but it was meant to be a very cheap purchase and even buying the battery is already making it very expensive.

Thanks again

Slystav

[retroleds]

The kindest advice I can give, considering that dark display: give up while you are ahead. A screen can be swapped out with one with the exact same matrix layout, but finding one is only cost-effective on extremely high-end pieces. Say 400GBP+. Your COmmador would be fun, but probably tops out at 75GBP in value. :(