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Re: [BCD396XT] Power Issues

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  • chris451
    Yes it was an OOOOPS. I had a dual bench supply and was testing something else, slipped. The 2nd half was set to 24v, but current limited, but there s enough
    Message 1 of 5 , Jul 4, 2013
      Yes it was an OOOOPS.
      I had a dual bench supply and was testing something else, slipped. The
      2nd half was set to 24v, but current limited, but there's enough energy
      in capacitors to put a failure spike on the other supply line.

      Re Chip caps. They are wonderfully small but terribly fragile.

      ON my numerous radios and scanners, the #1 failure is poor sensitivity.
      This was found to be due to the input connector solder cracking, or
      stress on the
      first RF coupling capacitor into the board. I keep 2 of each. Side by
      side one is fine and as expected and the other will have variable
      sensitivity, or it will change when the antenna is stressed.


      Usually the bad capacitor will fall into two parts when one end is
      unsoldered.
      One of the capacitor vendors of SMD parts has said
      direct contact with a soldering iron will cause microcracks.
      Freezing or stress will cause the part to split.
      To fix it, I try to put a stress loop on the antenna connection, and
      make sure the connector
      is tight.
      For the capacitor, I try not to touch the part except with tweezers, and
      reflow the adjacent solder
      rather than direct on the part.

      This problem has been found on handheld scanners or trancievers that I
      have owned.
      Brands I use: Icom, Uniden, Motorola. I have never had to fix a Motorola
      for that problem.
      A similar problem seems to recur on laptop power cords. See how Dell has
      addressed that on the D620--d820 laptops. Small inner conductor made of
      silver eliminates center pin stress.

      A good rule would be to make sure your antenna never touches anything
      that stresses it.
      Belt clips are the enemy of your product, as when you sit down extreme
      stress can occur.
      Antenna connections seem to be the first thing that breaks.

      Design wise, a larger SMD part does better than a smaller SMD part, so
      stay away from an 0402 or 0201 part where there will be mechanical stress.
      That is a hard lesson many have not learned.

      There are people like me that don't like the downtime and just fix most
      things myself.
      The radio was down for 3 days while the amp chip was sent and I had the
      zener already.
      I think I had to fix the antenna on that unit as well, but I've quit
      using belt clips or make sure to take it off before sitting in a car.
      I just feed it batteries from my rechargeable stockpile of AA's.
      I remember sending one of the bct396t into Uniden before and it was a
      couple of weeks and 80-90 bucks, before I got it back.

      I've seen another person on this list complain about not picking up
      aircraft.

      His unit could have a broken antenna connection so he can still get
      800mhz but that would degrade at VHF bands. The best thing is check it
      with a signal generator

      here's what I get on "good units"

      .5uv open .25uV close on a good uniden. 163.5mhz.
      .35 open .20uV close on an icr20

      am
      .28uv open .20uv close max squelch open 0.562uV on bct396xt am band
      121.5mhz.
      .15uv open .10uv close ic-r20

      Well I certainly hope UPman can help. I haven't seen anyone else ask
      that question.
      Here's another question. I'll just figure it out.

      Lets say I have a quick key programmed for a system. Under that system I
      have 10 banks defined.
      As I press shift and a number, I get sr1, sr2, sr3 ... gps (as a
      secondary mark on the keys).
      That shift + a number used to turn the groups on or off.
      I get a star for an off group and a number for an on group. But holding
      Func and pressing a key immediately produces the function marked below
      and to the right of the buttons.
      So my question is how do I turn the groups on and off other than
      navigating through the menu to the group lock/unlock? Sometimes I can
      change that while scanning, but its not always the case.
      Oh I figured it out.
      Scan the quick key (for example 1 with groups 0 to 9 defined.) Hold
      func. key till it locks to that system and F key holds without being
      pressed. This does a system hold and enables banknumber keys. In this
      mode press a number to turn a group on or off.
      If having trouble getting F hold to stop on a system increase the hold
      time to 10 seconds.
      I'm sure its in the manual but hard to remember.

      Always forget this one.


      On 7/4/2013 7:48 PM, John Stark wrote:
      >
      > Plug the wrong supply in could have done it.
      > I'm still trying to figure out how you crack a cap though as that just
      > shouldn't happen. Even soldering them shouldn't do that unless using a
      > soldering iron that's way too hot. With today's electronics much of
      > the solder used doesn't need much heat compared to 15 years ago. But
      > then with all the SMT technology that makes sense as the parts can't
      > take the heat of soldering the old parts did.
      >
      > Sent from my Verizon Wireless 4G LTE DROID
      >
      > "red2965 ." <mdmitchell65@... <mailto:mdmitchell65%40gmail.com>>
      > wrote:
      >
      > >I'm lost I been doing electronics for almost 40 years and have seen a lot
      > >of changes, but , tell me ....how do you accidently drop 28v(ac/dc) on a
      > >little ol 6v????
      > >much less how did it get that high in the first place.
      > > they are absolutely correct about the sams it is almost impossible
      > to get
      > >them unless you are a tech for that particular product.
      > >
      > >
      > >Mark
      > >
      > >
      > >On Thu, Jul 4, 2013 at 7:25 PM, MCH <mch@...
      > <mailto:mch%40nb.net>> wrote:
      > >
      > >> **
      > >>
      > >>
      > >> Aside from what John said, you likely stressed a lot
      > >> of other components in the scanner. It would be best
      > >> to send it to Uniden for repair (or replacement).
      > >>
      > >> You can get it to working condition only to have
      > >> another issue come up a month or two later.
      > >>
      > >> Joe M.
      > >>
      > >>
      > >> John Stark wrote:
      > >> > Uniden doesn't let schematics out for their own protection. As for
      > >> fixing the scanners its usually cheaper to let Uniden do it and get
      > it done
      > >> right with approved parts. Its doubtful UpMan can give you details
      > on the
      > >> chip in question, again to protect themselves.
      > >> > A lot of electronics manufacturers don't give out schematics to
      > keep the
      > >> competition guessing. The days of opening something up and fixing it
      > >> yourself are nearly gone for a lot of things.
      > >> >
      > >> >
      > >> > Sent from my Verizon Wireless 4G LTE DROID
      > >> >
      > >> > chris451 <chris451@... <mailto:chris451%40hotmail.com>>
      > wrote:
      > >> >
      > >> >> This is for UPman
      > >> >>
      > >> >> I'm a guy that likes to fix it if I can.
      > >> >> I accidently dropped 28 volts across the 6v line on a BC396xt.
      > >> >> I picked up another one to compare voltages.......and get the
      > first one
      > >> >> running again.
      > >> >> This high voltage incident took out a TI audio amp that was shorting
      > >> the 6v.
      > >> >> It also blew a zener hanging on the power jack.
      > >> >> After I replaced the amp and zener, it powers up but doent like
      > to run
      > >> >> on external power.
      > >> >> Also it degraded the dual mosfet that switches between external and
      > >> >> battery,
      > >> >> (a small SOT 6 pin part down and to the right of the charge jack
      > ) so I
      > >> >> can run on battery and sometimes I can charge it but not
      > consistantly.
      > >> >> So I'm trying to figure out if that mosfet is a dual N Dual P or
      > a pair
      > >> >> N and P.
      > >> >> My thinking is its a dual P channel but the part marking is a
      > mystery.
      > >> >> UPman can you take a look at the schematic on the power inlet
      > and tell
      > >> >> me what the dual MOSFET part is? Then I'd have it perfect again.
      > As it
      > >> >> is I have to swap batteries to keep it going,
      > >> >> I think the radio sees low voltage on an A/D and thinks the input
      > >> >> voltage is off.
      > >> >> Also since it wont run on the power jack I can't upgrade
      > firmware til I
      > >> >> get that fixed.
      > >> >> I believe Uniden would say send it in but I haven't checked into
      > that.
      > >> >> Can send a photo if you need it...would be nice if Uniden
      > published the
      > >> >> schematic for this like Icom ane everyone else does, and
      > alignment info
      > >> >> if any.
      > >> >>
      > >> >> I have the BC396T and it is not as sensitive as the BC396XT, is that
      > >> due
      > >> >> to improvements in the design or do I have a 'sick' bc396t? I
      > have had
      > >> >> to repair the input capacitor which gets cracked with use and breaks
      > >> >> apart. I've learned you are not supposed to touch the capacitors
      > with
      > >> >> soldering irons directly as this starts a crack which will
      > eventually
      > >> >> break the part.....
      > >> >>
      > >> >> Keeping them running................chris
      > >> >>
      > >> >> On 7/4/2013 5:08 PM, Uniden UPMan wrote:
      > >> >>> Flashing HOLD indicates you are in system hold mode. To get into or
      > >> >>> out of that mode, press and hold HOLD for a few seconds.
      > >> >>>
      > >> >>>
      > >> >>> UpMan
      > >> >>> UpMan FAQ: http://info.uniden.com/UnidenMan4/UpMan -- Please read
      > >> >>> before emailing me directly
      > >> >>>
      > >> >>>> ________________________________
      > >> >>>> From: "glg-swl7687@...
      > <mailto:glg-swl7687%40comcast.net> <mailto:glg-swl7687%40comcast.net>"
      > >> >>> <glg-swl7687@... <mailto:glg-swl7687%40comcast.net>
      > <mailto:glg-swl7687%40comcast.net>>
      > >> >>>> To: BCD396XT@yahoogroups.com
      > <mailto:BCD396XT%40yahoogroups.com> <mailto:BCD396XT%40yahoogroups.com>
      > >> >>>> Sent: Friday, July 5, 2013 6:59 AM
      > >> >>>> Subject: [BCD396XT] Flashing HOLD
      > >> >>>>
      > >> >>>>
      > >> >>>>
      > >> >>>>
      > >> >>>> Hello,
      > >> >>>>
      > >> >>>> How do I remove a flashing "HOLD" display during ID Scan?
      > >> >>>> BC396xt radio.
      > >> >>>>
      > >> >>>> Thank you for the help.
      > >> >>>>
      > >> >>>> Greg
      > >> >>>>
      > >> >>>>
      > >> >>>>
      > >> >>>>
      > >> >>>>
      > >> >>> [Non-text portions of this message have been removed]
      > >> >>>
      > >> >>>
      > >> >>
      > >> >>
      > >> >> [Non-text portions of this message have been removed]
      > >> >>
      > >> >>
      > >> >>
      > >> >> ------------------------------------
      > >> >>
      > >> >> Yahoo! Groups Links
      > >> >>
      > >> >>
      > >> >>
      > >> >
      > >> >
      > >> > [Non-text portions of this message have been removed]
      > >> >
      > >> >
      > >> >
      > >> > ------------------------------------
      > >> >
      > >> > Yahoo! Groups Links
      > >> >
      > >> >
      > >> >
      > >> >
      > >> > ----------------------------------------------------------
      > >> >
      > >> >
      > >> > No virus found in this incoming message.
      > >> > Checked by AVG - www.avg.com
      > >> > Version: 9.0.932 / Virus Database: 3204.1.1/5964 - Release Date:
      > >> 07/04/13 08:05:00
      > >> >
      > >>
      > >>
      > >>
      > >
      > >
      > >
      > >--
      > >Mark ~
      > >
      > >
      > >[Non-text portions of this message have been removed]
      > >
      > >
      > >
      > >------------------------------------
      > >
      > >Yahoo! Groups Links
      > >
      > >
      > >
      >
      > [Non-text portions of this message have been removed]
      >
      >



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