Re: 4 S Tuner Malfunction Query

David Furst

Robert, I also just built the 4S tuner and had similar problems to what you described.  I found that the wires from switch SW1 were touching the switch body (the metallic part) thus shorting the XCVR line to ground.  Check to see if you have very high resistance from the center pin of the XCVR BNC (J2) to chassis ground with the switch in the OUT position and the antenna disconnected.  You should also have some resistance (abt 94 ohms) with the switch in the IN position.  You don't have to disassemble the unit to measure this point. If you have a grounded J2, check the wires at the switch:  NONE should be touching the switch body.  This was just a careless mistake on my part and once I moved the wires away from the switch, the unit worked fine. Initial visual checks didn't reveal the wires touching unless you look at the switch from the side. Hope this helps.
Dave Furst WA3INF

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