Re: Pin Confusion #u3s

Mont Pierce KM6WT

On Sat, Feb 6, 2021 at 05:19 AM, KI7MWA wrote:
Page 15 of the U3S construction manual says: "To run the transmitter using the 5V supply, be sure to connect a wire between the +5V and PA pins. This is shown by the short red horizontal line in the diagram (below)."  But, in the diagram there are actually TWO short red horizontal lines, one between the second and third pins of the 4-pin header next to the capacitor labeled C1, and another between the second and third pins of the 11-pin header at the edge of the board, the pins labeled +5 and Heat.

With no jumpers installed, my DVM shows continuity between the +5 and Heat pins.  Is this correct? Or do I have a short somewhere?

At the bottom of the U3S webpage (click here) there are two diagrams from the PCB layers showing the traces in the board.

In the left image, you can see what pins are already connected, so helps to understand how the jumpers are described in the assembly manual.

The PA track is separate and thicker, to allow applying a higher voltage to the PA only.

The +5V Heater track is thicker to allow more current.


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