Anotherpower.com Forum
The Corner Tavern. => The Bar => General Electronics Discussion => Topic started by: Norm on January 29, 2012, 11:21:16 pm
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When new the digital readout was black, bright and clear.....but after a
few years it started getting gray and dim, so I checked the button batteries
and total voltage of the two 357s was 2.54 , nominal voltage is 3v for the
2 in series..so I gave it voltage from 2 AA batteries externally .....no difference
but it is almost like original when viewed from a 45 degree angle or a digit is
black if you press on the screen right over it.
any thoughts on how to fix this? :(
thanks....
Norm.
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Norm,
LCD's require vlotage on a contrast pin to function. I'm guessing the voltage supply to the contrast pin isin't working. The voltage can be positive or negative and is usually greater than the logic voltage. Often it is a charge pump power supply. If you can get a number off the display you may be able to track down the pinout. Many of them have the same pinout.
HTH,
Jonathan
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Is there a place that I can google for the display screen
these things are a big mystery to me just a rectangular
piece of like glass a small block looks like rubber (but isn't of course)
fits between the glass and copper paths on the pc board.
That little square of glass is what you replace?
Norm.
BTW thanks!
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Might be totally off base here Norm, but sounds like a similar problem I had with a meter. As it was hooped
anyway, I cleaned (gently) the rubber with an alcohol swab, then did the same, but less gently with the board.
So far, it's working. Not sure if it was actually dirty, or if the alcohol softened the rubber, or if I just got
lucky.
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What are you doing on a treadmill Norm
You should be peddling
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I invested 30 minutes searching for LCD troubleshooting and had fun reading this site -
http://character-lcd-module.com/LCD_knowledge.html (http://character-lcd-module.com/LCD_knowledge.html)
From their 'who makes your flat screen display' section...
"Basically they buy from a Original Equipment Manufacturer (OEM), claim to have a secret extra special feature then stick a new sticker on it and bill you thousands extra for the sticker. If you really want to pay thousands for a sticker please call our sales dept and we will sell you a sticker with our website logo for much less then the couple thousand you will pay ..."
From quick reading the earliest & cheapest monochrome LCD displays have a fluid that dies just from age - the troubleshooting procedures I've seen so far call out a specification, around 25%, for display module current flow drop that signals end-of-life for the glass assembly. Repair is remove & replace.
From my history with repairing them, once you've lifted the silicone-rubber connectors all bets are off it will ever work as-new again. Some will, some won't. There is chances on conductive gel on the contacts that has crept around and thinned to reduce power transmission or allowing leakage voltage to bypass the module, moisture saturating the contact area and killing conductivity, or the mechanical latch-clamp force that holds it aligned has let up some from whatever reason and its not longer getting full signal strength jumping across the umptyzillion contacts.
So... inspect with magnifying glass to see if silicone oil has spread out like an oil stain :o , let module bake in sunlight to see if some moisture is driven off 8), and poke at it scientifically ;D to see if the rubber connector block has relaxed and a little extra pressure darkens the display..
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Mystery solved.....
Madlabs....No and yes on the voltage on the contrast pin.
BJ.....Cleaning with alcohol and a q-tip might have helped
if that had been the problem....but it wasn't...but it didn't
hurt either.
Woof...Not on a treadmill .....wouldn't be caught dead on one ....unless
I turned the Treadmill motor....a regular treadmill makes as much sense
as being tied behind a slow moving car.....
dang....From reading what was on that site you were entertained
and this that was posted probably entertained so all in all you haven't
wasted your time
From my history with repairing them, once you've lifted the silicone-rubber connectors all bets are off it will ever work as-new again. Some will, some won't.
Cleaning with alcohol I'm sure would help them .....
.....but here's what I did....there are 2 button batteries each one had 1.24v total 2.48.
....so I charged one up with my solar panel (3 VW panels in series)opened the back
door....sun shining on the top 2 panels...charged one of the 357 buttons for about 2
minutes.=1.7....dropped down to 1.6......popped it back in it's place....and the display
is noticeably darker digits....so I done the same with the other ....and Ta Dah !
sucess.
(blush)....well I would have tried new batteries and when I was in the newly opened
Dollar General in Albion, Pa. I spied them ....a package of 3....357s ! ....I started to
reached for them and recoiled in horror! Like from a striking rattlesnake! $5.50 ! :o
No way ! .....well now that I know the batteries would have worked .....Maybe DollarTree
has them ....like 2 in a package for $1 ? :)
Thanks for all your help guys....hopefully we all learned something....
and it was fun.
Norm.
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Glad ya got it working!
Jonathan
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yeah me too but will have to get new batteries those didn't hold up very long
gue ss they'reo really rechargable.
Norm
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I started to reached for them and recoiled in horror! Like from a striking rattlesnake!
Me Too!
Except two LR44s for my digital micrometer.
Ended up with a 99-cent toy cell phone full of candy.
Two LR44s, 2 spares, and candy, 99 cents.
I like candy.
G-
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Forgot about this posting but hey Ghurd.....
in at DollarTree and yes 6 of the right size
battery buttons for a Dollar ! ....don't
that beat all ! sometimes it makes me sick to
think of all the different prices !
Norm.