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From: Interpol Date: Fri, 13 Mar 1992 Subject: Here Can You Find Some Modifications For The Uniden Bearcat BC200XLT And BC205XLT. Organization: Northwestern University, Evanston, Illinois Speeding up the scan and search rates for the Uniden BC200XLT and BC205XLT you will need a small crystal or ceramic resonator in the 600 - 800 kHz range. STEP 01: Disassemble the unit to access the microprocessor area a Slide off the battery pack STEP 02: Remove the two screws from the rear of the scanner and the two screws that hold the battery retaining spring at the base then remove the spring STEP 03: Carefully pry the bottom of the rear cover from the scanner and remove the cover STEP 04: Locate the two small screws at the base of the circuit board and remove them gently pull the front panel from the main frame at the base and separate them. If you separate them between the two layers. Remember that for later reassembly; the pins will have to be lined up perfectly before you slip the sections back together. STEP 05: Search around the logic CPU board Uniden calls it the MICOM PCB Assembly, and locate Y-201, which is a little rectangular component this is the stock 400 kHz resonator. Your replacement can be a bit larger if necessary, but not grossly so STEP 06: Carefully desolder and remove Y-201 put it in safekeeping because you may want it for something else someday STEP 07: Install solder your newly procured replacement clock resonator, be it a crystal or another ceramic resonator, where Y-201 came out STEP 08: Reassemble: Insert top of the front panel into the slot under the volume and squelch control panel. Carefully noting the alignment of the dual in-line connector at the bottom of the board with the mating socket, press the front panel firmly into place. Be sure that the holes at the bottom of the circuit board line up two screws and tighten them. STEP 09: Replace the rear cover by inserting the top of the cover into the slot under the volume and squelch control panel press cover into place insert and tighten the screws. STEP 10: Reposition the battery retaining spring slotted side toward notched hole insert the two remaining screws and gently tighten them. STEP 11: Slide the battery pack into place switch scanner on to ensure that the display comes on. If not, the battery may be discharged or the dual in line connector may have been misaligned during reassembly in step 5. Another possibility would be that the new resonator either doesn't work, is unsuitable, or may have been incorrectly installed. Another possibility if you installed something greater than 800 kHz is that it's just too fast. Assuming that the display comes on, leave the antenna disconnected, and run a speed test. Speed in channels per second equals the number of channels divided by the time in seconds. Using a Murata-Erie 800 kHz Note that the channels must have frequencies programmed into them Empty or 0000.000 MHz channels run faster and throw off the calculation. In addition to the shortened delay time, the user reports that the panel lamp will time out. Doubling the clock frequency halves the light on time. There is a variable extended delay modification in the World Scanner Report, to large to duplicate here. Also, in Volume 1, Number 4, Bill Cheek reports that the UC-1147 CPU has the necessary large chunk of memory on board, so you're stuck with 200 channels you can get the World Scanner Report here: Commtronics Engineering PO Box 262478 San Diego, CA 92196. The Scanner Modification Handbook I and II are available from the same address. They're something like $17.95 each + $3 P & H. The World Scanner Report is $25 per year. From: interpol. Date: Fri, 13 Mar 1992 Subject: Uniden Bearcat BC200XLT And BC205XLT Battery Indicator Modification Organization: Northwestern University, Evanston, Illinois Here's are some modifications to help remedy the BC200XLT and BC205XLT low battery indicator blank out feature, courtesy of Bob Parnass. BC200XLT LOW BATTERY FIXES: Troy T Pummill, N6XMV. Here are two small articles from MT. I have not tried these modifications, do so at your own risk your mileage may vary from monitoring times. FROM MT JUNE 1990, PAGE 98 BOB'S TIP OF THE MONTH ... BC200XLT SHORT BATTERY LIFE SOLVED: Short battery life sometime only an hour or two between charges seems to be the only major complaint among owners of the leading hand held scanner, the Uniden Bearcat BC200XLT. Presumably, owners of similar sets like the BC100XLT the BC205XLT, and the Cobra 4030 could have the same problem. Now that is an ailment of the past. It turns out that the batteries were not really at fault a zener diode which determines the voltage at which the low battery indicator would come on was defective in some units, causing the circuit to actuate prematurely. Replacing that diode and changing the value of an associated resistor pro vides the answer. Free fix MT contacted Uniden and was assured that they will provide the fix for free, even if the radio is outside of the one year warranty period. If your Uniden BC200XLT suffers from short battery life, send the radio along with a brief note describing the ailment. To Uniden Customer Service, 9900 West Point Drive, Indianapolis, Indiana, 46250. As shown in the accompanying diagram, zener diode D203 and resistor R208 are the parts in question. D203 should be about 7 volts and R208 should be 150,000 ohms. These are miniature surface mount devices on double sided circuit board if your radio is under warranty, attempting this fix yourself will void that warranty. SHORT CUT MARK MACHCINSKI FROM WYANDOTTE: Michigan, came up with his own solution. He simply soldered a wire bridge across diode D203, disabling the low battery indicator entirely. The radio now operates uninterrupted until it blanks out when the battery level drops to about 4.5 volts. Yet another suggestions from a Canadian reader would bridge the original diode with a 6.8 K resistor, defeating the premature recharge signal, yet preventing the battery from too low a discharge. FROM MT JUNE 1990, PAGE 98 BOB'S TIP OF THE MONTH ... BC200XLT AND BC205XLT BATTERY LIFE TIME EXTENSION: Part II Every time we run a helpful hint on a popular product, some one find an even more helpful hint. This one disable the low battery cutoff circuit and adds several hours of operation to a single charge. Our lab unit was still going strong after seven hours straight. Uniden will provide the fix for free, but if you're in a hurry and don't mind voiding your warranty, read on. Note this modification should not be attempted by anyone unfamiliar with small circuit board components. THE TOOLS REQUIRED ARE: A Small Phillips Screwdriver, Fine Tip Soldering Iron And Solder Wicking Braid. THE PROCEDURE: Remove the battery pack, then the two screws form the bottom spring clip. Carefully pull the rear cover off, bottom first. Remove the two small screws at the base of the circuit board. Pull the front panel away from the mainframe, bottom first. At the bottom of the remaining board to the left of the speaker magnet are two. Blue electrolytic capacitors; just above them are two striped components one resistor and one diode. Using the soldering iron and braid, carefully remove the two components without overheating the board or damaging the copper traces. When you reassemble the radio, be very carful to note the insertion of the front panel into the slot at the base of the volume/squelch panel. Be especially careful to align the screw holes perfectly, allowing the two rows of fine pin contacts to mate correctly with the socket. If this is not done correctly and it probably won't be the first time no damage will occur, but the scanner display will be blank. Recharge your batteries after 6 to 8 hours of heavy use. If the scanner dies, recharge it as soon as possible to prevent loss of your memorized frequencies. From: Interpol. Date: Fri, 13 Mar 1992 Subject: Uniden Bearcat 200XLT Cellular Restoration Modification. Organization: Northwestern University, Evanston, Illinois. Yet Another Uniden Bearcat BC200XLT And BC205XLT Modification, Courtesy of Bob Parnass And Other Good People: UNIDEN BEARCAT BC200XLT AND UNIDEN BEARCAT BC205XLT - CELLULAR RESTORATION: Note it is unlawful to monitor cellular telephone conversations. It is possible to monitor signals from the deleted ranges even without conversion. Simply add 21.7 MHz to the deleted frequency and enter the higher image frequency. Reception is virtually identical in strength to that which would be heard on the deleted frequency. The frequencies deleted at the factory may be restored, but the procedure must not be attempted by anyone unfamiliar with electronic circuitry. Grove Enterprises assumes no liability for damage caused by this procedure. The modification will void your warranty. THE TOOLS REQUIRED ARE: A Small Phillips Screwdriver And A Small Wire Cutter. STEP 01: Slide off the battery pack and remove the antenna from the scanner. STEP 02: Using a small Phillips screwdriver, remove the two screws from the back of the scanner, the two screws which hold the battery retaining spring at the base and the spring itself. STEP 03: Carefully pry the bottom of the rear cover from the radio and remove the cover. STEP 04: Locate the two small screws at the base of the circuit board and remove them gently pull the front panel from the mainframe at the base and separate them. STEP 05: Locate the 64 pin quad flat pack microprocessor IC labeled Uniden UC-1147 and the 10 K resistor with the colors: brown - black - orange. Leadless resistor positioned above the letters DEN on the IC. STEP 06: Using miniature wire cutters, cut the resistor body in two without disturbing anything else near it If the left solder pad comes loose, it may be peeled from the board. Brush or blow away any residue. This completes the restoration reassembly. STEP 07: Insert the top of the front panel into the slot under the volume and squelch control panel and, noting carefully the alignment of the dual inline connector at the bottom of the board with the mating socket, press the front panel firmly into place. Be sure that the holes at the bottom of the circuit board line up with the holes in the plastic standoffs below them. Insert the two screws and gently tighten them. STEP 08: Replace the back cover by inserting the top of the cover into the slot under the volume and squelch control panel; press the cover into place, insert and tighten the screws. STEP 09: Reposition the battery retaining spring slotted side toward notched hole, insert the two remaining screws and gently but securely tighten them. STEP 10: Slide the battery pack into place; switch the scanner on to make sure the display comes on. If not, the battery is discharged or the dual-inline connector was misaligned during assembly see step 7. Assuming the display comes on, press: Manual, 845.0, E; within two seconds, the frequency 845.000 should appear on the display cut this resistor. From: Interpol Date: Fri, 13 Mar 1992 Subject: Uniden Bearcat BC200XLT 136 - 174 AM Modification. Organization: Northwestern University, Evanston, Illinois. HERE'S THE LAST OF THE BC200XLT AND BC205XLT MODIFICATIONS: I know of downloaded off of a local BBS here in Chicago Modification for Putting BC200XLT or BC205XLT in AM Reception Mode. I have come up with a crude modification for the BC200XLT scanner to allow AM reception in the 136 to 174 range. Why would I want AM in this range you ask ? well I attend several Air shows during the year and the Thunderbirds use 140 MHz area frequencies. As we all know the Uniden switches to FM in this range, causing very distorted reception slope detection. Somebody else may have already thought of this idea you ? but here goes. Break the AIR Trace between dual diode D31 and IC1 pin 8. Connect the center of a single pole - double throw mini switch to the trace leading back to IC1 pin 8. Connect one of the other poles to the trace leading back to D31. This is the Normal mode. This just restores what you have cut. Now connect the other pole to the VHI VHF HI line at a easy to locate point. This is the AM mode. What will happen now is when AM is selected the VHF and VHF air band will all be in the AM mode UHF and others are not affected. When in the normal mode everything is just like it always was. I have done this mode over a year ago so it's still a cloudy in my memory. But it works like this the micro processor sends a high to Q7 to select the AIR mode, by routing the VHI signal around D31 by means of the switch the AM detector is reselected. Normally D31 blocks out the VHI signal allowing FM in the VHF HI range. I hope my explanation of this modification is clear. It does take some delicate surgery to do. I also hope I haven't duplicated anyone else's idea. Thanks From, Billy Wiggins |
