Products > Test Equipment
Upgrading the HP/Agilent 8714C from green CRT to color LCD
TiN:
Badass mod, reviving gear like a boss. :-+
Zero999:
--- Quote from: TheSteve on December 27, 2015, 08:33:44 am ---The LED strips I ordered 1.5 months ago finally arrived. They are long thin strips of white LED's mounted on PCB. They were shipped in a strong plastic tube to prevent damage yet some how the postal system still managed to fold the tube right over. This of course snapped the LED strips into pieces, they also managed to damage the included switching power supply. The LED strips I ordered were the shortest I could find on ebay but were still too long. As luck would have it the broken pieces were the correct length to convert the LCD screen to LED backlighting and to ditch the CFL tubes and inverter. They were also broken at just the right place as the LED's are in parallel sets of three LED's in series.
The original CFL tubes just slid out with no panel disassembly at all. I added some heatshrink tubing to the LED strips which gave them a nice snug fit when slid in to the LCD panel. For brightness I used a power supply to find what I thought was the optimal drive current and then added a single 20 ohm resistor in series with the LED strips which connect to the 12 volt power supply. So for now the brightness is fixed.
A further project is to use the original 8714C knob to vary the brightness. The pot is 100K so I'll need to come up with a simple linear based circuit(no noise) that can vary the current to the LED strips between 100 and 200 mAh.
Once installed the LCD looked same of course but has instant on backlighting with no inverter noise at all. I have attached pics of the original tubes and new LED strips.
--- End quote ---
Good work!
Here's a constant current LED circuit which should do the job.
nctnico:
Thanks :-+ I never knew those LED based CCFL replacements existed!
plesa:
:-+ Upgrade!!
Howardlong:
Very impressive!
I did the Newscope LCD mod to my 8753A some months ago, it's taken two decades off it. Of course there's no VGA output on the 8753A, they have an FPGA to do the CRT untangling.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version