Bright Future: Jornada 720/680 CCFL to LED upgrade

Hi All,

A few of my J720's have a dim dull screen due to aging compact fluorescent backlight. For $10 dollars or so, LED backlights are available and can easily be trimmed to proper size. I am still working on the power/brightness control... but here is a view showing the difference between one of my brightest ccfl J720 vs the new LED installed on a J680 screen. It's a work in progress but gives proof of concept. Notice how uniform the backlight looks... at high intensity.

More to follow...

Joval

Addendum: I've found replacement ccfl backlight replacements for the same price... $10. So I may compare the two new ccfl vs LED, as it is obviously much easier to swap out the ccfl with same and not tinker with power and dimming control for LED (which I hope is easier than it sounds). Whichever works in bright outdoors will be my choice as the J720 is too dim for most outdoor viewing on sunny days.

Edited by joval 2022-03-05 8:07 PM








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CCFL vs LED backlight.png (169KB - 5 downloads)
DSC01693.JPG (127KB - 3 downloads)

Man, this is incredible and you have some serious courage to pop the hood and just start throwing parts over your shoulder.

Congratulations,
Jake

Hi Jake!

Thanks! I think this is a game changer... I took the J680 outdoors in full bright sunlight and could actually see the screen quite well!!! Usually I have to seek out shade and even then is near impossible to see anything...

Easily powered by the Jornada ccfl backlight power connection/tap.

Now I just have to put a transistor and resistors together as the Jornada brightness keys only change the dimming voltage from 8.86v to 10.6 volt low to high ... the LED power board dimmer control range is 12volts (dark/off) to 0.0 volts (max bright). A Mosfet with the proper reverse bias should do the trick, just speculating with my limited know how.

I'll see if I can take a picture...

Joval

Addendum: All is not perfect as the LED driver requires 9 volts and is really bright on 12 volt AC, however on battery power voltage drops to 8 volts and although much improved, screen is not near as bright on battery... ideally may need a boost inverter added for outdoor battery use.. the plot thickens.

Edited by joval 2022-03-06 12:23 AM

I wait with bated breath to hear your next move.

Jake

Wow, that's night and day (pun intended). Do you think you will be able to successfully wire it into the brightness controls?

Could be a good tutorial for a CESD if you're willing to write one up, joval.

I would be interested to know what the immediate difference is on the battery life moving from CCFL to Led. One would assume that the saving would be significant.

It does seem counter intuitive that 12v would be min brightness and 0v max brightness.

Nice work. Someone made a LED mod with his 680 back in 2006.
https://web.archive.org/web/20060617024748/http://sprite.student.utw...
I think you also need some kind of microcontroller for brightness/power ...

Stefan

I remember that Stefan...

WOW!!! Joval, nice work!

My biggest concern would be opening the display. I wouldn´t like to get my Jornadas damaged. Are there any screws or is it all self contained with glue?

Nice work, the CCFL's in my Jornada's are not as bright as they used to be so I was thinking of replacing them but LED seems like a better option if a control board can be rigged up especially as it might have the added bonus of improving battery life!

Yes, I'm in... just need to optimize the power side of things. I ordered the LED strip well over a year ago, it was about $10 but price is a bit high now so I don't recommend getting it from Amazon... there are cheaper units now for much less, however this one the power drivers fits inside the case with slight mod) so now finally putting things together:



The LED is just plain brighter so is using slightly more power. Rough comparison CCFL is at best medium bright uses 110ma @12volts, approx 140ma@9volts. The brighter LED strip is 210ma@12volts, 232@9volts using the included LED driver. I measured the milliamps running the Jornada without batteries, powered off my metered bench power supply/soldering station and with screen turned on and turned off (by toggling the "alt + Calender key" and subtracting the cpu power useage when screen was off)

The LED strip has 42 LEDs in series of 3 at a time (3x3volt=>9volts input), 5 LEDs per inch (or 3 Leds per 1.5 cm). Cut the Strip at the 6 1/4 Inch mark (has 1.5 cm increments marked on backside) which gives 30 LEDs to fit Jornada screen including 1/4 for wire connectors. See below photos.



Thanks Stefan. Yes, I was aware of that LED mod... he made his own strip @ 40 volts and designed his own boost converter as LED driver.

These strips are already assembled with 5 LEDs per inch, in series of 3 so 9 volts... which is a bit high for J720 battery power about 8 volts. Super bright when J720 plugger into AC 12volt supply!

So, yes, I think I need to build a simple custom boost converter to get the best brightness options and it will also allow dimmable. Studying up on LED boost circuits such as this: https://youtu.be/bJjN_5xed64?t=109

Rich: What happened to all the lonely widows chasing after you... you weren't charged with "assault with a dead weapon... were you??... not again??!!



Small torx screws under the HP and Jornada720 "stickers" at base of screen near hinges, not very difficult, no glue, like cell phone has snap-in plastic catches so technique matters as they break... use fingernail or credit card. Details later or google Jornada teardown.



Really doubt much improvement there because once you see a brighter screen during daylight you want the brightness. Most CCFL vs LED use close to same power, IMO, maybe a 20% gain with hi-efficiency LED driver perhaps. Included LED driver is good size to fit into Jornada case but may not be optimized power efficiency. Will explore.

Here are some pictures below.

Joval




Edited by joval 2022-03-07 11:48 PM










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Cut LED at 6.25inch line(red paperclip).JPG (203KB - 1 downloads)
LED Driver fits case.jpg (124KB - 0 downloads)
30 LEDS fit in 6 inches for J720(680).JPG (163KB - 0 downloads)

OK, with screws and clips I will give it a try. Seems ok for trying it on an already "scratched" model.

Back in the days they even added homemade backlight to the HP95 and HP200. There was a page online from Daniel Hertrich (the guy who came up with the idea and later sold the service to do it). He once showed it to me, it was a bit tricky but the result was astonishing. You didn´t see any hints on the modification till the light brightens up.

Maybe you can get some ideas from the concept. The description must be in some archives today.

I can write up a walk-through on how to access the CCFL lamp and how to swap it out with the LED strip if needed. Easy peezy.

I think I have the boost converter in hand: and will try it soon, then all I need is to reduce its size to fit into the screen case along with the present LED driver.

You won't believe what a bright improvement it will be!

best,

Joval