CFA635 loses a lot of brightness with age?

[gschizas]

I recently bought a second CFA635 (for my other PC) and the difference in brightness is huge! My old CFA635 was actually one of the first (more or less), but seeing them now side-by-side, the new one is about 10 times more bright (i put the brightness on my new CFA635 to about 10% to achieve a similar brightness as the old one).

Unfortunately my camera's battery was completely spent (I think I need a new battery), so I'll probably post a picture tomorrow.

Both CFA635's are blue with white letters, and both work from an external USB. I have the old one for less than 3 years (I know I was using a smaller red CFA631 for my old box, and I was still using it for my next box in July 2004)

What I'm interested to know is whether it is considered normal behavior to lose that much brightness in the course of just 3 years (and probably less), or the first units were defective in some way and new models don't lose brightness?

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[Heffo]

It's the nature of LED backlighting to dim over time with use. I have a 633 that the blue backlight has dimmed somewhat. The best suggestion to preserve the brightness of the backlight is to use the dimming & shutdown features of CrystalControl so that the backlight is not (or less) active when you are not using your PC.

 

[gschizas]

That much? It's like day and night here!

On the left is the old one, on the right the new one:

With flash:



Without flash:



When not using flash, it's really off the scale!

Obviously both are at the same settings, 100% brightness and 50% contrast.

 

[Heffo]

That looks about right. The rated lifetime of a white LED is about 50,000 hours. If you leave your PC on all the time and the backlight constantly on then we get...

24hrs (1 day) * 365 days (1 year) * 3 years
24 * 365 * 3 = 26,280hrs

So, if the end-of-life of a white LED is 50% of original brightness after 50,000 hours then you are already over half-way through the life of the backlight, and you would be sitting at about 75% of the original brightness, which from the photos you posted, looks about right.

If you look through the backlight sections of the character LCDs that CrystalFontz sell, the ones that use white LEDs usually give a suggestion to turn down or turn off the backlight during inactivity.

Edit: There is also a note on page 18 of the 635's datasheet about the lifetime of the backlight.

 

[reider]

I wouldn`t rely too much on what the percentages are showing. I`m sure its different from one LCD to another, even on the same model. CF Admin or Tech will give you more details.

Reider

 

[CF Tech]

We rate all of our current white LED backlit products at 10,000 hours.

The white LED backlight lifetime has been worrisome for us. We have found that many of the LED manufacturers and backlight manufacturers seem to be quite over-confident on the lifetime numbers that they post.

We are in the process of redesigning all the backlights of the white LED backlit modules. I think the new CFA-634 design is shipping or in the production pipe. The CFA-635 redesign has just been approved, so those new modules will be coming to customers soon. The CFA-631 white LED backlight has also been redesigned.

The new design uses more LEDs that have better efficiency, running them at significantly lower current (and therefore lower temperature, and therefore longer lifetime). The overall initial brightness is better, and overall current is lower.

 

[gschizas]

And I just bought one more... Oh well, I guess I'll be buying a new one for my old PC once the new CFA635 is out... I think I've bought at least 4 LCD modules up to now, 2 631's and 2 635's. The first 631 was destroyed by the (IMHO) bad design of the USB connector*. I guess the 2 635's will just have to live out their backlight hours...

* The USB connector is designed so that the cable is inserted parallel to the board. So when the cable is pulled too fast (by accident), it rips off the connector from the board. A better design is that of the SCAB connector, where if the cable is pulled too fast, the worst that can happen is that the cable is pulled of and maybe some plastic is bent. Maybe I should put that complain in another thread though...

 

[CF Tech]

We have the USB connector on the CFA-631 fixed now:

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