/ parnass@cbnewse.att.com (Bob Parnass, AJ9S) / 9:33 am Jun 11, 1991 / *From the RCMA Journal, April 1989: * LOW BATTERY INDICATOR IN THE UNIDEN/BEARCAT 200XLT SCANNER * * I have not attempted to alter the 200XLT low battery cir- * cuit, but it looks like there are a few ways for an adept * technician to fix it: * * 1. The threshold could be reduced if D203 were to be * replaced with a zener diode of lower voltage. * 2. The low battery circuit could be bypassed completely * using one of two methods: * * a. by removing D203, and connecting the input of * regulator IC204 to the output of IC208, a 5 volt * regulator, or * b. by removing R208, and replacing D203 by a jumper * wire. I have one of these scanners on order, in the meantime I bought a book: "Radio / Tech Modifications number 3". For the BC-200XLT they list two modifications. The first is to remove R-215 to unlock the cellular phone frequencies. The second is to remove D-203 and R-208 to "extend battery life". Thats all they say. I haven't seen a schematic, and I'm not going to blindly try this. You sound somewhat familiar with this animal, any comments? Frank Ball frankb@hpsad.HP.COM pyramid!hplabs!hpsad!frankb Path: microsoft!uunet!uunet!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!dsinc!bagate!b1y1m39 From: b1y1m39@bagate.BELL-ATL.COM (Bob Esposito) Newsgroups: rec.radio.amateur.misc Subject: Re: Low Battery Indicator on Bearcat 200xlt Message-ID: <1991Jun14.164301.22962@bagate.BELL-ATL.COM> Date: 14 Jun 91 16:43:01 GMT References: <9106121339.AA00811@lanslide.hls.com> <27890001@hpsad.HP.COM> Organization: Bell Atlantic Lines: 45 In article <27890001@hpsad.HP.COM> frankb@hpsad.HP.COM (Frank Ball) writes: >/ parnass@cbnewse.att.com (Bob Parnass, AJ9S) / 9:33 am Jun 11, 1991 / > >*From the RCMA Journal, April 1989: >* LOW BATTERY INDICATOR IN THE UNIDEN/BEARCAT 200XLT SCANNER >* >* I have not attempted to alter the 200XLT low battery cir- >* cuit, but it looks like there are a few ways for an adept >* technician to fix it: >* >* 1. The threshold could be reduced if D203 were to be >* replaced with a zener diode of lower voltage. >* 2. The low battery circuit could be bypassed completely >* using one of two methods: >* >* a. by removing D203, and connecting the input of >* regulator IC204 to the output of IC208, a 5 volt >* regulator, or >* b. by removing R208, and replacing D203 by a jumper >* wire. > >I have one of these scanners on order, in the meantime I bought a book: >"Radio / Tech Modifications number 3". For the BC-200XLT they list two >modifications. The first is to remove R-215 to unlock the cellular >phone frequencies. The second is to remove D-203 and R-208 to "extend >battery life". Thats all they say. I haven't seen a schematic, and I'm >not going to blindly try this. You sound somewhat familiar with this >animal, any comments? > > I thought Uniden identified this problem and changed the value of the D203 diode. I'm looking to purchase a new 200XLT and would like to know if this is still a problem??? I had a 100XLT and sold it mainly because of the low battery nonsense, but it was an early model. -- ====================================================================== Bob Esposito Voice: (215) 466-6831 Bell Atlantic Corp. FAX: (215) 563-3984 Philadelphia, Pa. E-mail: espo@bagate.BELL-ATL.COM Path: microsoft!uunet!uunet!cis.ohio-state.edu!pacific.mps.ohio-state.edu!linac!mgweed!cbnewse!parnass From: parnass@cbnewse.att.com (Bob Parnass, AJ9S) Newsgroups: rec.radio.amateur.misc Subject: Re: Low Battery Indicator on Bearcat 200xlt Summary: original 4/89 article exposing defect in 200xlt Message-ID: <1991Jun11.163348.7963@cbnewse.att.com> Date: 11 Jun 91 16:33:48 GMT References: <1991Jun7.052253.15731@sequent.com> <7719@mace.cc.purdue.edu> Organization: AT&T Bell Laboratories, Naperville, IL Lines: 73 In article <7719@mace.cc.purdue.edu>, larsenp@mace.cc.purdue.edu (Paul Larsen) writes: > As I tried to tell the person who posted about this previously, I have the > same problem with my BC100XLT and in my opinion it all has to do with > battery memory....... >From the RCMA Journal, April 1989: LOW BATTERY INDICATOR IN THE UNIDEN/BEARCAT 200XLT SCANNER by Bob Parnass, AJ9S Some Bearcat 200XLT scanner owners don't get the battery life they expect. They report having to recharge the slide on NiCd (Nickel Cadmium) battery pack after as few as only 3-1/2 hours of operation. Last month, I discussed the results of several tests made on the 200XLT portable scanner to determine its current con- sumption. This month, I propose cures for the overly con- servative low battery indicator problem. As presented earlier, the 200XLT low battery indicator begins to flash when battery voltage decreases to 7.2 volts or less. This starts a 10 minute timer within the 200XLT. After the low battery indicator has flashed for 10 minutes, the 200XLT display blanks. The low battery indicator in three 200XLTs examined is too conservative. Owners have been known to get up to 2 hours more use from the NiCd battery pack after the low battery indicator begins to flash. The 200XLT Service Information Manual specifies the low bat- tery threshold should be 6.9 volts nominal, with an accept- able range of between 6.5 and 7.2 volts. However, the 7.2 volt threshold measured in 200XLTs is almost out of range. Zener diode D203, type HZK3CLL01TR, a surface mount com- ponent located on the Micom (microcomputer) circuit board, determines the low battery detection threshold. I have not attempted to alter the 200XLT low battery cir- cuit, but it looks like there are a few ways for an adept technician to fix it: 1. The threshold could be reduced if D203 were to be replaced with a zener diode of lower voltage. 2. The low battery circuit could be bypassed completely using one of two methods: a. by removing D203, and connecting the input of regulator IC204 to the output of IC208, a 5 volt regulator, or b. by removing R208, and replacing D203 by a jumper wire. The only drawback I could see is that defeating the low battery circuit might cause memory loss when the bat- tery voltage becomes too low, because the microcomputer doesn't detect the low voltage soon enough. Again, the previous suggestions are conjecture, as I have not tried either modification. Readers are cautioned: experimenting with the 200XLT circuitry is risky. The sur- face mount parts are tiny and the land patterns on the cir- cuit boards are fragile. -- ============================================================================ Bob Parnass, AJ9S - AT&T Bell Laboratories - att!ihlpy!parnass (708)979-5414 Path: microsoft!uunet!uunet!sequent!muncher.sequent.com!washer From: washer@sequent.com Newsgroups: rec.radio.amateur.misc Subject: Re: Low Battery Indicator on Bearcat 200xlt Message-ID: <1991Jun11.231419.7982@sequent.com> Date: 11 Jun 91 23:14:19 GMT References: <1991Jun7.052253.15731@sequent.com> <1991Jun10.220140.5939@cunixf.cc.columbia.edu> <7719@mace.cc.purdue.edu> Sender: news@sequent.com (News on Muncher) Organization: Sequent Computer Systems, Inc. Lines: 63 In response to Paul's statement that this is all caused by battery memory... I'll state again, that the battery is reading nearly 7.0volts with 600ma load on it .... sustained! This does not sound like a battery with a memory problem (if such problems exist, given recent net postings on the subject). I did receive the following e-mail From Adam Keith Levin, that contained a letter he received from 'Jim Summers, KD7F' AKL>>A comment on the current required to hold the memory contents: AKL>> AKL>>The .5 mA measured with the power switch in the off position is not AKL>>the current required to maintain the RAM contents in the processor. AKL>>Rather, it is being drawn by a voltage divider used to create a 5.6 AKL>>volt regulator using a 3 terminal 5 volt regulator. A 10K resistor AKL>>is placed between the regulator output and the ground terminal of the AKL>>regulator IC. The regulator will force 5 volts across this resistor AKL>>and therefore .5 ma will flow in it. The ground terminal of the AKL>>regulator is connected to battery ground through 1.2K. This .5 ma AKL>>will flow to battery ground through the 1.2K raising the regulator AKL>>ground terminal .6 volts above battery ground. AKL>> AKL>>The reason the designers wanted 5.6 volts from this regulator was to AKL>>provide 5 volts on the other side of a diode which is used to isolate AKL>>the regulator from the capacitor which holds the memory contents when AKL>>the battery pack is removed. The RAM is located in the CMOS processor AKL>>(IC201) so this 5 volt regulator provides the Vdd for the processor AKL>>when the scanner is on. AKL>> AKL>>I was able to reduce the switch off current drain by a factor of 10 AKL>>by replacing the resistor between the ground terminal of the regulator AKL>>and battery ground (R243) with a diode, and increasing the value of the AKL>>10K resistor (R244) to 100K. AKL>> AKL>>Low battery warning: AKL>> AKL>>I have also modified the low battery warning circuitry in my scanner AKL>>so that the warnings start at 6.6 volts (originally 7.2V in my unit.) AKL>>I had no data on the part (IC-204) that acts as a comparator to detect AKL>>low battery voltage so I experimented with a resistive voltage divider AKL>>in place of the zener diode (D203) and 150K resistor (R208). I ended up AKL>>with a 5.11K in place of the diode and a 10K for R208. This circuit AKL>>will draw .5 ma or so from a fully charged battery but this is negligable AKL>>compared to the total current requirements of the scanner. (This current AKL>>only flows with the power switch on.) AKL>> AKL>>While these modifications have increased my satisfaction with my AKL>>BC205XLT, I would not recommend them to people who have not had some AKL>>experience working with surface mount components. Static discharge AKL>>precautions should also be taken. Proceed at your own risk! AKL>> AKL>> AKL>> His second point, about the indicator coming on at 7.2 volts, is probably the culprit. I'll have a shot at his mod, or something similar, and post the results. jim KG7HH 1-503-578-3171