LIGHT MOD FOR THE BEARCAT 235XLT TRUNKTRACKER!! From Sly Kapchinski, N5GQB This mod will enable you to turn on your backlight via a separate switch and to leave it on as long as you desire. No longer do you have to keep hitting the light button all the time to see who's talking while at night. Before I begin I must say that I have had this mod on my radio for several months now with no ill effect on the radio. I leave the light on all night while scanning with the radio on the night stand. As for the extra battery drain, it is not as bad as you might think. I did some milliamperage checks on the radio and here's what I found. The radio pulls between 70 - 85 MA while on, squelched and no signal present. The variance depends on if your trunking or not, scanning or manual, the frequency band your on, etc. With the light on, the radio pulls an additional 20 MA (approx). So you can see, by leaving the light on all the time will not severely cut back on battery life. My personal experience you will loose about 2 hours of battery life if left on continously. However if you are able to plug the scanner in, it is probably best, especially if you leave it on at night while you sleep. There is a couple of small drawbacks to the mod. #1 The backlight will still continue to shine even after the low battery indicator has shut the radio off. If left this way the batteries will continue discharge to nothing. This is not good for the batteries. However, this will not happen (of course) if left on the charger. Please note though, the light "DOES" go off when the scanner is turned off by the knob. #2 Depending upon your preference and the size/type of switch you choose to use, it may be necessary to drill a hole in the case. Other things you'll want to know #1 The regular light button will function as normal.As long as your added switch is not turned on. #2 The keypad lockout button functions as normal regardless of added switch position. #3 This mod will more than likely void your warranty. *However see "my idea". #4 Your scanner will not lose any of its memory. Unless you leave it taken apart, day in - day out. DISCLAIMER I assume absolutely no responsibility if you blotch the job. This mod will more than likely void your warranty. (see my idea!) You will be required to solder to a surface mount transistor. If you do not have experience in messing with SMD's or the necessary equipment then I suggest you do not proceed or let some one who has the experience do it for you. I am in no way related to, tied to, or work for Uniden, any scanner retailer, wholesaler or repair shop. I am merely an individual with a somewhat electronic background and an interest in scanning like yourself. Like mentioned before. I have done the mod myself and it works just fine. Lastly, if for some reason your scanner has a different layout of the identifying components than as to what I describe below then don't proceed. Guessing will only get you in trouble. Direct any comments/questions to n5gqb@txcyber.com Supplies you'll need #1 A low wattage soldering iron with a tiny tip. You will be soldering to surface mount devices! #2 Very small gauge wire, about a foot and cut in two pieces. I would recommend 26 gauge or smaller and stranded. Once again you'll be soldering to smd's! You cannot put any undue stress on these components! I would not use magnet wire. #3 Lastly you'll need to locate a s.p.s.t. switch (not a momentary either). Your choice of switch depends on the way you want to mount it. I recommend two mounting situations. #3A) Involves drilling a hole in the top of the radio just behind the earphone jack. I highly suggest you take the radio apart so you can see what you're doing before drilling and to see if you can fit a switch into this small void area. Such as a micro-mini toggle switch. Also note there is a metal plate underneath the plastic top that you'll need to drill through. This will be evident once the radio is apart. You'll probably need to shop around some specialty electronic stores.I don't think radio shack has anything small enough. However confirm for yourself. I would recommend you take the radio apart first and look at your size options and/or mounting locations to give yourself an idea of what you need. "MY IDEA" #3B) The second switch option involves no drilling, in fact if you go this way you can remove the whole mod with no evidence! You will need to locate a small enough switch to fit inside the battery pack area. I used a switch that is about half the size of a fingernail and about an 1/8 inch thick, it resembles a single "dip" switch that you might would find mounted on a circuit board. It has a tab on it for the switch so I can use my finger nail to flip it. It fits nicely in the lower right corner of the battery pack section (yes the battery and cover is installed and I can swap out packs with out interfering with the switch as well). I mounted the switch to the case with some strong double stick foam tape. Remember you don't have to do exactly as I did just use some "enginooity". I obtained the switch I used from "Ace Electronics" in Houston. "How this mod works" The switch will be hooked up to a switching transistor inside the radio that is normally responsible for acting like an on/off switch for current to the backlight. You will in effect be bypassing the current around this transistor, like a jumper. This transistor normally receives a timed signal from the cpu to allow current to flow to energize the backlight. You will not be hooking up to the cpu but to the transistor. As stated before this mod has no ill effect on the radio. Unless of course you foul up. "Lets get started" 1. Start by removing the battery cover, battery pack, antenna, volume and squelch knobs (they pull off), remove the round nut for the bnc connector (I use a small pair of needle nose to grip the slots). 2. Remove the 4 black screws holding the back cover on and remove back cover. Don't worry about removing the screws for the belt clip. 3. Remove the top cover as well. 4. With the radio pointing up and the back facing you, remove this first circuit board by carefully! grabbing it at the top and bottom and carefully! rocking it top to bottom. It is held in place by a multi pin connector on the bottom right side. The pins are held in place by resistance, do not worry about having to release some tab or anything to get this board off. However, do not use anything to pry with and do not use excessive force. This is the only thing holding this board down. Once removed set this board to the side. 5. Remove the next board by removing the 2 silver screws at bottom, The 2 silver screws in the center of the metal plate shield and the 3 silver screws holding the metal shield itself. This board should now come out. 6. Release the two tabs holding the metal shield on, they are on either side of the lcd display. 7. Now turn this circuit board to the left. The component side should be facing you and the lcd display (on the underside) should be facing to the left. 8. Locate the 2nd largest chip on the board, it is labeled IC202, mine has the numbers D7225GB on it. Now, about a 1/4 inch from the "top right" corner of this chip (going to the right) you will see a 3 legged black component. This is the transistor you need to hook up to. It is the only 3 legged component on this whole left side of the board. Mine has the numbers 64 and 23 on it. This transistor should be easy to identify as this board is not very crowded. There are some smaller resistors and capacitors around it. As for another desription as to its location, its half way between IC202 's top right corner and the screw hole in the circuit board. Remember to have the circuit board facing in the direction as described in step 7! 8. With the board still facing the same way you will need to solder one wire to the top left leg of the transistor, then solder the other piece to the single bottom leg. REMEMBER DO NOT LEAVE THE IRON ON THE COMPONENT MORE THAN A SECOND OR YOU'LL WIND UP BURNING IT UP OR MESSING UP THE SOLDERING PAD OR TRACE! BELIEVE ME ITS VERY EASY TO DO! 9. Now route your 2 wires to your switch! Be sure to leave plenty of slack and be real easy about this. Do not pull or tug on at all where its been soldered to the transistor! BE SURE TO DOUBLE CHECK THE SOLDER JOB WITH A MAGNIFYING GLASS. Make sure its secure, no cold joints and no bridges exist. 10. Put your radio back together and confirm operation and your in business!! Direct any questions/comments to n5gqb@txcyber.com