Repairing an LCD display

[AgX]

I just repaired a 12 years old telephone base station where the LCD display meanwhile turned blank completely. That display does not have pressure contacts but a plastic foil with printed conducting paths which is glued/laminated to the LCD’s base glass and the LCD’s printed circuit board. After quite some time I found out that this foil somehow lost electrical contact, though on visual inspection and mechanically it seemed totally right.

After further experimenting I realized that applying heat of 180°C and pressure reinstalled electrical contact. I used a digitally controlled solder iron with a screwdriver type of tip.

After quite some delicate work with a head loupe I succeeded in getting nearly all pixels work again. Only at three contacts I spoiled it as the tip used was slightly wider than the contact zone, and and at these three contacts I seemingly cut the printed conducting paths of the foil at the point where the foil runs over the edge of glass base plate. So it seems a good idea to chose a tip a little less wide than the contact zone, but not too small (no pencil tip) in order to spread pressure evenly.

I’m curious for how long my repair will last…

 

[Ralph Javins]

Good morning, AgX;

The Antex Precision soldering iron made in England has several sizes and shapes of interchangeable tips available. The smallest tip I have for mine is the 1/32 inch or 0.75 mm diameter cylindrical tip. For working around recent SOIC and other high density contacts for integrated circuits, it has been very helpful.

 

[Phillip P. Dimor]

I have/had an Antex soldering iron, 15W with a gold-plated needle tip (the finest one available for the iron). It's worth the money, great iron. Heats up extremely fast, nice even heat. The tip was sweet but delicate.
I love those irons.

 

[AgX]

too early been pleased...

Today the display faded totally again.

Well, that probably means that I should be more sceptical on any goods with LCD displays in future.

 

[nickc]

I don't know if this is still a live post, but here goes:
Canon in their T80 user manual gives the life of the LCD at about 5 years, and suggests taking it to a repair depot after that time for replacement. As the T80 was one of the first cameras to have a large lcd on it, I wonder if any display of similar vintage might have time expired?

 

[AgX]

Does that suggestion by Canon refer to the time since manufacture or the active (switched on) time? I don't know.
Anyway, the displays of my T90 are still fine. Though, as others, I am worried.

This case of attempted repair by me was on a telephone and not the actual LCD failed but its contacts. Though the effect is the same. And LCD's can be contacted different ways.

 

[Andrew K]

Canon actually put the lifespan warning into the service manuals to cover themselves against a mass of future warranty claims.

Back in the 80's no one knew for sure how long an LCD was going to last?

In the time I repaired cameras for Canon Australia I think I replaced 1 LCD that was faded/dim out of maybe 500 repairs involving faded LCD's...most faults involved damaged LCD's (90% of repairs) where the cameras were dropped.

The other 10% was divided into dirty/faulty connector strips - maybe 5%. The other 5% involved a faulty circuit board where the PCB was faulty and wasn't driving the LCD correctly...

 

[AgX]

Great to learn that at least this problem maybe not as serious as commonly stated.

 

[benjiboy]

My Canon T90 was made in September 1986 and the LCD display is fine, I have three bodys and they are all fine, there must be tens of thousands of them still about like that.

 

[Ray Rogers]

I used a digitally controlled solder iron with a screwdriver type of tip.

Whats a "digitally controlled solder iron"?

Can you dial in your desired tip temperature?

 

[AgX]

Yes. In contrast to the classic ones that run on the mains and just get to some equilibrium with the air around and cool down with each soldering action again, these controlled ones are running on low voltage and have a temperature probe near the tip. Thus a feedback regulation can be applied via the transformer unit where one also can set the temperature over a wide range. With the current models there is a digital display of temperature.

 

[Ray Rogers]

Cool, That's Hot!

I will look for them on an upcomming trip to Electric Town (Akihabara) later this week.

Ray