Nepro DSM

[charger105]

Hi All.
Recently I picked up this Nepro DSM LCD:



I've put a battery in it and I get nothing. I know the displays on these are very temperamental. This one looks OK, but I've been told this means nothing.

I wasn't expecting it to work, but would like to at least give it a chance before declaring it a 'display piece'. It's in NOS condition, so it will make a nice 'display piece' if I can't get it going.

Any suggestions on where to start. I've never worked on one of these.
Rgds,
Andrew.

[fronzelneekburm]

Very nice piece! At first i would start with cleaning all contacts, that means each square milimeter of metal the battery can touch. Carefully scratching with a knife can usually be enough for a small test. Don't forget - after 30 years most metals could have oxidized. Check for any traces of leaked battery acid, usually greenish crystals that look a bit like stained bronze are clear signs of an acid massacre.

From the pic i can only say the display looks not acid-burned or bleeding, but that must not mean a lot.

Double check your batteries. You'd laugh how many watches have been declared dead just because they were tested with dead batteries or contacts being oxidized or contact clamps being bend off/missing, so the batteries can not establish electric contact with the back of the watch (most vintage watches use the watch back as an electrical conductor, so clean this too).

if you can make sure it is no contacts problem then the air is getting thinner. From now on analysis is getting more complicated, most pros maybe would start with a multimeter searching for dead conductors or similar. Use much love and patience - some old watches can behave odd when they get powered on after 30 years, so they may not immediately display something or need some kind of reset or button pushing.

[charger105]

Thanks Fronz.
The module is as clean as a whistle.......like new !
I was hoping someone may have had some experience with this particular module, and may have had some "handy hints".

I think I might try to measure the display voltage. If there's 20V at the display, then the display is probably the issue. Azimuth_pl suggests this here:

http://www.dwf.nu/viewtopic.php?t=2749

Rgds,
Andrew.

[azimuth_pl]

I'm back after a long while.
I would say that your Nepro is dead and all that based on that poor picture.
the shine and color of a good (functioning) display should be different.
I've had some 10 or more of these.
if it's silver mirror shine then it's very likely dead as the crystals have escaped somewhere over the years... don't ask how and where :)
a dead display with liquid crystals in place should be cream-yellow due to aging of the crystals and some bubbles or empty mirror-silver spots should be present (spots where the crystals have disappeared).
a functioning Nepro/Microma display after all these years should be light-cream.
check Peter Wenzig's website for big pictures. all of them show decay.

[charger105]

Thanks Piotr. Good to have you back ! Have you been travelling ?

I've had another look at the display, and where the digits are, is a silvery mirror colour. Around the edges I can see traces of yellow area where the crystals must still be in-tact. It looks like this one is well and truly dead.

I've got an Optel DSM which is very nice. Display is degraded, but still works. Interesting that the Optel displays are much more long-lived than the Nepro/Microma ones. I've only ever seen one working Nepro/Microma, and even that display is degraded (on Peter Wnzig's site).
Whilst on the subject, I recently got a load of Optel parts, and in it are all the parts for the square DSM module. The date on the IC is 1972, so this would've been an extremely early example. A shame that it's been taken to pieces.

Rgds,
Andrew.

[azimuth_pl]

the mirror color on the display is the background on the glass. so if you see this color only it means that the display has lost vaccuum and the crystals have evaporated. it might still display some digits in places where the crystals are still present but it depends on the condition of the crystals. if they are yellow they are dried out completely.

I wish I could travel :)
a lot of projects at work, at home and on my workbench.
I have moved into new fields of exploration and worked a lot on deco jumphours, early quartz and electrics.
I have decided that I do not need to be tempted to buy any more LEDs because I already have some 30 Pulsars and some 5 Barry Synchronar lots that have been waiting for some 18 months.
so the best solution is not to search or read about LEDs because I will never finish all the projects that are in the pipeline :))