Jerry,
Thank you; I'll try those steps.
73,
Mark/WU6R
On September 12, 2019 at 3:21 PM, "Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:
Mark,
>>? I double checked for polarity being backwards and it is wired correctly...
>? ? The bench power supply is outputting 12v and 2 amps, but at the bitx the voltage drops to 0.49v
So, you measure 12v across the power supply and at the same time you measure 0.49v
across the Bitx40?? Then somewhere there is 11.51v drop across a bad connection,
you should be able to find that with a voltmeter.
If that power supply is sending out 2 Amps, that means 2 amps * 11.51 volts = 23 Watts of power
getting dissipated across that bad connection, and it is smoking hot.
I doubt that is the case.
My guess is that you see 12v at the power supply until you turn on the Bitx40,
at which point the power supply goes into current limiting and drops to around 0.49v.
Try unplugging PA-PWR (which gives 12v to the IRF510) and unplugging the Raduino.
Does it still drop to 0.49v?
Then something is dissipating 2 amps * 0.49v = 1 Watt, and if you feel around
the board with your fingers you will probably find something that's getting warm.
And that will be where the fault is.
If that doesn't find it, then disconnect stuff (with power off) until the voltage at the Bitx40 pops up to?
12v where it should be when you turn the power supply back on.??
Verify that the TX power rail has 0.0 volts on it (relay K1 is not stuck on).
If so, then the fault is in either on the 12v rail or the RX rail, as labeled in the schematic.
I assume you still see something like 0.49v on the 12v and RX rails when power is on,
perhaps somewhat less due to voltage loss with 2 Amps flowing through the power supply
wires and board traces.
You may be able to find the fault by measuring all points in the schematic labeled as either RX or +12v,
the point with the lowest voltage on it (some small fraction of a volt) should be near the fault.
If that doesn't do it, you may have to start removing parts or cutting traces to all places?
labeled RX and +12v in the schematic.? You know you are very close when you cut a portion
of the circuit out and the power supply now goes up to 12v when turned on.
Good luck!
Jerry, KE7ER
