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69748Re: RXTX ensemble Trouble

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  • Jaco Le roux
    Nov 4 1:12 AM
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      Hi All,

      I have checked the output to ground on the 5volt regulator with my DMM and got a 10 Ohm reading. I have lifted all the IC's pins connected to the 5v track and still find it to be 10 ohms, If I select continuity on the DMM it beeps and give reading of 10ohm.

      This might be the problem I have with the 5volt that only measure in at 1.3volt, even the input side of the 5volt where it should be 12volt I only measure 3.5volt, I think something is shorting but I can't find where.

      Where can I start....


      --- In softrock40@yahoogroups.com, "Jaco Le roux" <zs3jlr@...> wrote:
      > Hi Alan,
      > I have had sometime to look at my RXTX, I found that it draws 114mA on the 12volt side with out USB, I have checked the voltage of the 5 volt Regulator and found that it only gives me 1.3 Volt out and get hot, on the input side I only measure 3.5volt. I have removed the 78L05 and tested the current draw at 0.40mA without USB.
      > On the input line of the 78l05 there is 12volt with 78L05 removed.
      > I also found that when every thing is connected to PC and I tap on the pcb, sometimes it starts receiving but not for long.
      > I can't see any short anywhere, and don't know where to look anymore.
      > Thank you
      > --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
      > >
      > >
      > > ----- Original Message -----
      > > From: "Jaco
      > > Subject: [softrock40] Re: RXTX ensemble Trouble
      > >
      > >
      > > >
      > > > Something is seriously wrong here, I have tried to TX when all is running and does seem to tx but with now power out, I have set
      > > > my other radio to a frequency and TX from the RXTX, I can hear myself but the meter does not reflect any power out, While TX'ing I
      > > > took the board in my hands to see If there could be something ells that I can see and when I touched the 2N2222 heat sink the
      > > > audio on the receiver radio become very loud, but still nou output, Will this be part of the same problem I'm having or what ells
      > > > could be the problem.
      > >
      > > This does seem to be a second fault.
      > > But you must ignore this until the first is cured.
      > > One thing at a time. Get the RX correct first.
      > >
      > > >>
      > > >> This time it lasted for 41min, it still the same.... I'm starting to think that the Si570 is damaged.
      > > >> > OK, Let me put it this way, every time I re-solder the Si570 and plug it in it works for a while, So I have done this test,
      > > >> > I have disconnected everything for about 20min and reconnected it to the PC, It worked again.
      > > >> > Now, I have found that the Si570 does get hot but not like in very much, Tested temp round about 42 - 45 Degrees C.. (not a
      > > >> > good thermometer)
      > > >> >
      > >
      > > The Si570 temperature seems about normal but, yes, it could be faulty.
      > >
      > > Have you checked the joints on pins 2 and 6 of U1? U1 could be faulty but I have never known one to fail in this way.
      > >
      > > Make absolutely sure that components and voltages around U1 and U3 are correct and soldered well with any excess around the Si570
      > > removed with solder wick.
      > > Then maybe it is time to try a replacement Si570.
      > > It would be easier to try a new U1 first but I feel that is not so likely.
      > >
      > > 73 Alan G4ZFQ
      > >
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