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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>Hello everyone !<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>From the RCA Receiving Tube manual RC-28 –<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>A 35Z5 or 35W4 wants the following resistance in shunt with the filament tap when a #47 lamp is used:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>DC output current of 70 ma, 800 ohms<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>DC output current of 80 ma, 400 ohms<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>DC output current of 90 ma, 250 ohms<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>A #47 lamp, 6.3 volts at 150 ma would be 42 ohms.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>So, RCA appears to recommend 42 ohms paralleled by the resistance(s) shown above at the various current levels.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>Which means somewhere between 39 and 47 ohms should work OK in lieu of a lamp. It shouldn’t be too “fussy!”<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>Using the LED system – suggestion: hook up the LED across the pins (2 & 3). If the LED doesn’t have an integral full-wave bridge rectifier, or isn’t two LED’s in parallel providing full wave conduction, put a bridge in series with the LED. Measure the current. Shunt the pins with additional resistance to bring the current to its correct value.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><br>And now your rectifier filament should be as happy as a clam – however happy clams are!!<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>Note: the open circuit voltage across pins 2 & 3 may reach 15 volts with no lamp or resistor load.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>Good luck !!<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>Mike/<o:p></o:p></span></p><div style='mso-element:para-border-div;border:none;border-bottom:solid windowtext 1.5pt;padding:0in 0in 1.0pt 0in'><p class=MsoNormal style='border:none;padding:0in'><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>K5MGR<o:p></o:p></span></p></div><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p><p class=MsoNormal>Mike Langner<o:p></o:p></p><p class=MsoNormal>929 Alameda Road NW<o:p></o:p></p><p class=MsoNormal>Albuquerque, NM 87114-1901<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>(505) 898-3212 home/home office<o:p></o:p></p><p class=MsoNormal>(505) 238-8810 cell<o:p></o:p></p><p class=MsoNormal><a href="mailto:mlangner@swcp.com">mlangner@swcp.com</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>