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15714Re: T3-135 Power issue

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  • kg6bnl
    Jul 3, 2013
      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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