Re: uBITX woes, feeling disheartened. #ubitx

Arv Evans

If you look at the schematic you can see that D7 is directly across the windings of relay K1.  The cathode
end is connected directly to +12V.  The other end is connected to the collector of Q15.  If you do not have
+12V at the cathode of D7 you should check for +12V on pin-1 of your power plug.  If no +12V there you
may not have the power supply ON or it is not connected to the power plug.   Scroll down for more
troubleshooting suggestions.

​If you have +12V at the power plug but not +12V at the cathode of D7 you should trace the +12V from
power plug to the cathode of D7 by following the +12V through your power switch and back to the
+12V connection (RED wire) which is on P1 on your uBITX main circuit board.    At P1 the red wire
should have +12V.  With the PCB disconnected from power and the Raduino board unplugged you
can measure continuity from the RED wire (+12V) on P1 to the cathode of D7.

Connecting +12V to your uBITX is a bit complex if you are not used to following schematic drawings
and doing a little circuit tracing as you go. 

This excerpt is from the uBITX Wire up instructions on the web page:
  • Solder the 1N4007 diode across the DC connector. The ring of the diode should go to the
    positive tab of the DC connector, the other side of the diode goes to the ground tab. (See
    the picture below)
  • Solder the DC cable’s red and brown wires together to the positive lug of the DC connector
  • Solder the black wire to the ground.

It might be easier if this section of the Wire up instructions said something like this:
  • The red wire provides power to all uBITX circuit except the transmit power amplifier. 
    The brown wire is for power to the transmit power amplifier section.

  • The Red (+12V) wire and transmit +12V (brown wire) can be connected together by
    connecting both brown and red wires together on the cable connecting to P1.  Do this if
    you are running your transmit power amplifier section from the same +12V supply as the
    rest of your uBITX transceiver.

  • If running the transmit power amplifier section from a separate supply you should use
    the brown wire only for that purpose.  Do not connect the brown and red wires together if
    using separate power for the transmit power amplifier section.
    NOTE:  If you use the red +12V wire through the power switch and connect the brown +RF PA
    power directly from the power connector to P1 on your uBITX PCB, the transmit section
    will be powered even when your front panel power switch is OFF.

  • The loose diode provided with the uBITX connects between +12V (cathode end) and
    ground (anode end).  This is a reverse-voltage protection diode that should short if power
    is accidentally connected backwards.

  • The ground tab on your uBITX power connector should connect directly to uBITX P1
    via the black wire.  This is the ground for all uBITX circuits and should be reasonably
    short to minimize possibility of ground-loops.  If using a metal chassis you should add
    a black wire between the power connector ground tab and chassis ground. 

​This may, or may not, help. 


On Sun, Feb 4, 2018 at 2:16 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
Read this old post, you should be able to follow along with your vom:

On Sun, Feb 4, 2018 at 12:31 pm, @AC8XZ wrote:
hello; ok I'm getting no 12 volts at D7 with ptt on and vom leads one on both des. sure do appicate all the help. so with no power at d7,where do I check next 73's de

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