Today I upgraded the LED's in my HP 5350B frequency counter. First, a huge thanks to Mr. Kerry Wong for his excellent writeup back in 2017
http://www.kerrywong.com/2017/01/30/hp-5350b-backlight-upgrade/My backlight board was a little different than Kerry's, but the steps and components for the upgrade were the same none the less. I figured I'd do a quick writeup of my upgrade, in case anyone else is planning to do the same.
As you may be aware, the 5350 has a terrible backlight from the factory. Practically invisible, really, under ordinary room light. Five very dim, yellow, LED's on each end of the display that edge-light the LCD screen. The upgrade is to use modern white LED's to replace them. Another issue I had was a lot of scratches and hazing on the plastic window covering the LCD. I didn't get any pictures of the process, but I solved this by using a small propane torch and gently "flaming" the surface of the window (once out of the unit) to polish the lens. I followed up with a microfiber towel and automotive "optical grade" polishing compound. It's not perfect, but it's FAR better than when I got the unit.
Another challenge was bending the LED's and positioning them for soldering. To solve this, I 3D printed a fixture that held the LED's at the proper spacing at exactly 4.85mm from the surface of the board to the bottom of the LED's. A bit of 3/8" Kapton tape held it in place during soldering. I think the results speak for themselves; all of the LED's are pointing straight and exactly at the proper height. I'll be sure to include a link to the file if anyone is interested once I get it hosted.
From here on out the pictures, along with Kerry's write up, pretty much speak for themselves. So without further delay, let's get to the pictures!
Parts: Digikey # 1516-QBL8IW30C-NW-ND (quantity 10).
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