Hi All >From my time working in a Ham repair shop I can say that if a power supply >dipped by more than 0.25 Volts between RX and 100w TX AT THE TERMINALS ON THE >CASE OF THE POWER SUPPLY then that power supply wanted either replacement or >repair.
I have just checked my own power supply for my K3 ( EP-925 or PS-30M badged linear PSU) and the voltage change (at the terminals on the case of the power supply) between RX and 100W TX is less than 70 milli-volts. This was measured using a both a Thurlby 1503HA (32000 count) or Fluke 8060A (4.5 digits) meters. The K3 is fed via 6 feet of 20 Amp cable and shows a voltage change between RX and 100w TX (on the K3 display) of no more than 0.6 Volts. There are no fuses in this lead but if there were I would allow an extra 0.1 volt per fuse giving a total of 0.8 volts. If the k3 showed a difference of 1 volt or more then that would be cause for immediate investigation. Put in its simplest form a voltage drop of 1 volt at 20 amps means that 20 watts of power is being wasted. In the example quoted by the original author we are seeing a drop of 3 volts at 17-.5 Amps a loss of over 50 watts (the equivalent of 4 Amps at 12.5 Volts)! Even the cheapest digital meters have a 200 milli-volt range and you can use this to measure the voltage drop across each junction in the wiring to find where the fault lies. I have cured many rigs that use the standard 6 pin connector of various problems simply by cleaning the power supply lead contacts throughout including the contacts between spade terminals and fuses and fuse holders and fuses. As a matter of standard practice all my crimp contact junctions are soldered as well as being crimped using a good quality tool. I hope this note provides adequate guidance. Regards Malcolm G0MIC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
