Thursday, February 09, 2017

Brighten up your scanner's LCD display

I recently moved from the back country to a more people-active area and had a need to upgrade my old radio scanner to a version that can understand EDACS trunking. While you can listen to trunking on a conventional scanner, it's annoying with EDACS and you can't follow any conversations, you only get random channels and talk groups.

I have been watching old Radio Shack scanners on ebay and set a limit of $40 for any purchases. So far I've nabbed a pair of Pro-97's and Pro-95's and a Pro-433 to go with my ancient Pro-2005 and Pro-34.

Love these scanners, for now they will work with the current trunking system. One problem, though: The Pro-95 has a really dim, ugly green back light on the LCD screen. Here it is, compared to the Pro-97 with its nice, bright orange display:

My goal here is to change this horrible display from green to orange. This modification will work on the nearly identical Pro-93 and probably the Pro-94 as well.

The only purchase I had to make was the surface-mount LEDs. I sourced them on ebay here. If that link goes dead, just search for LED 0603 orange. You could probably use size 0805 or 1005 but I wouldn't try any bigger than that.

Radio disassembly

It is quite simple to access the LED, just take care not to rip things apart. Take your time. Remove the battery cover and battery holder from the back of the radio and remove the four long screws.

Carefully pull off the back half of the case. Nothing is attached to it, just set it aside. Then carefully pull the rear PCB assembly away from the front PCB by detaching three plugs. One is on the left and the other two on the upper and middle right. The right-hand plugs are small, only two prongs and powers the LEDs and something else I don't know. The longer one on the left connects the two large PCBs. They come apart easily. The speaker wire will be attached. You can unhook it if you wish or leave it in place, it's not too bad to just fold the case off to the side.

Now you need to remove five screws to remove the front PCB from the front half of the radio case. Be careful here, the LCD screen will swing loose and the back light diffuser will fall out. Don't damage the small cable on the screen.

Removal and replacement of LEDs

Carefully flip up the LCD out of the way and be sure not to damage the cable. Remove the diffuser panel to expose the two LEDs you want to replace.

As you can see, the LEDs are quite small. For reference, I put a penny in the picture. The penny is 19mm wide. The LEDs are less than 2mm across.

Be sure to identify which polarity on your LED. The cathode will go on the right. LEDs can be marked differently, use Google to see types other than this.

Now for the intricate surgery. You need a very fine, low-wattage (I used a 12-volt, 15-watt) soldering iron and a toothpick. Wedge the toothpick under one side of the LED and desolder that side, the LED will pop loose on that side. Then remove the LED by desoldering the other side.

Sorry I don't have a picture of this step, both hands were busy!

Now position the new LEDs. Hold the LED down with the toothpick and solder one side then the other. It is NOT easy to keep the LED in place. You could try fine-tipped tweezers. I found the toothpick easier. You will be chasing around the LED on the PCB and it will flip over and spin around, but you'll eventually get there.

Once soldered in place, you can plug in the radio and test. Just be sure not to short anything out while it is disassembled. Remove the silicone keypad from the front case and place over the PCB and press the light button.


Put it all back together

Now we want to reassemble everything. Roll up a bit of cellophane tape and stick it where you want the diffuser to go. Mark the position of the LED receptacles on the very end (thin edge) to help you line it up, then stick it into place and carefully flip back the LCD. Leave this loose, because it'll inevitably sit crooked when you place the front cover back over the assembly.

Be VERY, VERY careful that the LCD is sitting properly in the front case, otherwise you will crack the screen when you tighten the five screws on the back.

Make sure you put the speaker cable back in the notch at the side of the front PCB, tighten the five screws to hold on the front case half (MAKE SURE NOT TO PINCH THE LCD SCREEN OR YOU WILL BREAK IT), push on the rear PCB with the three plugs lined up, put the rear case back on, tighten the four long screws, and you're done!

Not an exact match, but much, much brighter and easier to read than the lame green! I suppose yellow LEDs might be an alternative, a project for another day!