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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>A engineering friend of mine locally has been working hard to resolve issues with an IP-28 power supply. His findings follow:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>"I have come to the conclusion that the circuit design on the IP-28 has some serious issues with the power rating of the current limit pot. All power must flow through this series device and power dissipation of the pot would be around 30W at full voltage. The ten turn pot is only rated at 2W. I honestly do not know what the Heath engineers were thinking when they designed this one! I would suspect that other components in the load current path are also under rated; I know my unit took out three transistors in addition to the pot and another series resistor."<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Any thoughts on this problem?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Vr,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Gary H. Harmon, Jr. - K5JWK</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>6003 Archwood</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>San Antonio, TX 78239-1504</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>210.657.1549h / 210.884.6926c/t</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>"Retirement means every day is a Saturday except Sunday"<o:p></o:p></span></p><p class=MsoNormal>http://www.grissomroadcoc.org<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>