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T3-135 Power issue

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  • kg6bnl
    Hi, I have a T3-135 that I installed in a DR-135TP (I replaced the original EJ-41U with the T3-135). After installation I did not get any output on the serial
    Message 1 of 3 , Jul 2, 2013
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      Hi,
      I have a T3-135 that I installed in a DR-135TP (I replaced the original EJ-41U with the T3-135).
      After installation I did not get any output on the serial port, the LEDs did not come on, etc. I measured 3.5V on the 5V power line, which seemed pretty low. If I feed 5V directly from the DR-135 regulator into the power line on the T3, it comes up OK. The regulator is putting out around 4.8-4.9V.

      Looking at the schematic for the DR-135, it seems the power for the TNC module is going through a transistor (Q130, type DTA114YUA) which is rated for 70mA. I measured the draw at around 40-50mA running off the 5V line, and about 30mA off the transistor, so it shouldn't be exceeding the spec, but maybe the transistor is bad? I measured about 3.8V when the original EJ-41U is on, but it seems to work OK.

      Has anyone else seen a similar issue? I'd like to retain the ability to do voice, so I'd rather not just hardwire on the 5V line to the TNC.

      Thanks in advance,
      -Ben (KG6BNL)
    • Scott Miller
      I ve been told that at least some versions of the 135 have a programmable regulator, and doing a factory reset on the radio has fixed 5v power problems. Scott
      Message 2 of 3 , Jul 2, 2013
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        I've been told that at least some versions of the 135 have a
        programmable regulator, and doing a factory reset on the radio has fixed
        5v power problems.

        Scott

        On 7/2/2013 10:17 AM, kg6bnl wrote:
        > Hi,
        > I have a T3-135 that I installed in a DR-135TP (I replaced the original
        > EJ-41U with the T3-135).
        > After installation I did not get any output on the serial port, the LEDs
        > did not come on, etc. I measured 3.5V on the 5V power line, which seemed
        > pretty low. If I feed 5V directly from the DR-135 regulator into the
        > power line on the T3, it comes up OK. The regulator is putting out
        > around 4.8-4.9V.
        >
        > Looking at the schematic for the DR-135, it seems the power for the TNC
        > module is going through a transistor (Q130, type DTA114YUA) which is
        > rated for 70mA. I measured the draw at around 40-50mA running off the 5V
        > line, and about 30mA off the transistor, so it shouldn't be exceeding
        > the spec, but maybe the transistor is bad? I measured about 3.8V when
        > the original EJ-41U is on, but it seems to work OK.
        >
        > Has anyone else seen a similar issue? I'd like to retain the ability to
        > do voice, so I'd rather not just hardwire on the 5V line to the TNC.
        >
        > Thanks in advance,
        > -Ben (KG6BNL)
        >
        >
      • kg6bnl
        Hi, There didn t seem to be any kind of programmable regulator, but I tried a reset anyways and I got the same result. Thanks anyways. I realized that I have
        Message 3 of 3 , Jul 3, 2013
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          Hi,
          There didn't seem to be any kind of programmable regulator, but I tried a reset anyways and I got the same result. Thanks anyways.

          I realized that I have an original DR-135, and not a MKII/MKIII (I got it used and wasn't sure). Looking at the schematic of the DR-135 MKII, it seems they added a new 5V regulator to run the TNC, powered off the 12V rail (but still switched by the CPU). It doesn't look like they've changed the main regulator.

          I haven't wired it up yet but my plan is to get a 5V regulator with an ENABLE line (essentially doing what the MKII does) to solve this.

          -Ben (KG6BNL)

          --- In tracker2@yahoogroups.com, Scott Miller <scott@...> wrote:
          >
          > I've been told that at least some versions of the 135 have a
          > programmable regulator, and doing a factory reset on the radio has fixed
          > 5v power problems.
          >
          > Scott
          >
          > On 7/2/2013 10:17 AM, kg6bnl wrote:
          > > Hi,
          > > I have a T3-135 that I installed in a DR-135TP (I replaced the original
          > > EJ-41U with the T3-135).
          > > After installation I did not get any output on the serial port, the LEDs
          > > did not come on, etc. I measured 3.5V on the 5V power line, which seemed
          > > pretty low. If I feed 5V directly from the DR-135 regulator into the
          > > power line on the T3, it comes up OK. The regulator is putting out
          > > around 4.8-4.9V.
          > >
          > > Looking at the schematic for the DR-135, it seems the power for the TNC
          > > module is going through a transistor (Q130, type DTA114YUA) which is
          > > rated for 70mA. I measured the draw at around 40-50mA running off the 5V
          > > line, and about 30mA off the transistor, so it shouldn't be exceeding
          > > the spec, but maybe the transistor is bad? I measured about 3.8V when
          > > the original EJ-41U is on, but it seems to work OK.
          > >
          > > Has anyone else seen a similar issue? I'd like to retain the ability to
          > > do voice, so I'd rather not just hardwire on the 5V line to the TNC.
          > >
          > > Thanks in advance,
          > > -Ben (KG6BNL)
          > >
          > >
          >
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