<html><head></head><body><div style="color:#000; background-color:#fff; font-family:Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yui_3_16_0_ym19_1_1491660371757_13934"><span id="yui_3_16_0_ym19_1_1491660371757_13933">You need to read his original message again! He said 0.5 mA, not 5 mA. I have found that most of the 6146 family of tubes will put out full power at around 1.75 mA but not below. Between 2 mA and 2.5 mA grid current per tube is a good target. Anything above 3 mA will definitely shorten the life of the tube.</span></div><div id="yui_3_16_0_ym19_1_1491660371757_13934"><span><br></span></div><div id="yui_3_16_0_ym19_1_1491660371757_13934"><span><br></span></div><div id="yui_3_16_0_ym19_1_1491660371757_13934"><span><br></span></div><div id="yui_3_16_0_ym19_1_1491660371757_13934"><span id="yui_3_16_0_ym19_1_1491660371757_16876">The "." before the 5 is very easy to miss!</span></div><div id="yui_3_16_0_ym19_1_1491660371757_13934"><span><br></span></div><div id="yui_3_16_0_ym19_1_1491660371757_13934"><span><br></span></div><div></div><div id="yui_3_16_0_ym19_1_1491660371757_13936"> </div><div class="signature" id="yui_3_16_0_ym19_1_1491660371757_13937">Glen, K9STH </div><div class="signature" id="yui_3_16_0_ym19_1_1491660371757_13937"><br></div><div class="signature" id="yui_3_16_0_ym19_1_1491660371757_13937">Website: http://k9sth.net</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491660371757_13938"><br><br></div><div class="yahoo_quoted" id="yui_3_16_0_ym19_1_1491660371757_13942" style="display: block;"> <div style="font-family: Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_ym19_1_1491660371757_13941"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_ym19_1_1491660371757_13940"> <div dir="ltr" id="yui_3_16_0_ym19_1_1491660371757_13939"> <font size="2" face="Arial" id="yui_3_16_0_ym19_1_1491660371757_13956"> <hr size="1"> <b><span style="font-weight:bold;">From:</span></b> Kenneth G. Gordon <kgordon2006@frontier.com><br> <b><span style="font-weight: bold;">To:</span></b> Robert Wood <radiorob@swbell.net> <br><b><span style="font-weight: bold;">Cc:</span></b> Heath@puck.nether.net<br> <b id="yui_3_16_0_ym19_1_1491660371757_16942"><span style="font-weight: bold;" id="yui_3_16_0_ym19_1_1491660371757_16941">Sent:</span></b> Friday, April 7, 2017 8:22 PM<br> <b id="yui_3_16_0_ym19_1_1491660371757_16944"><span style="font-weight: bold;" id="yui_3_16_0_ym19_1_1491660371757_16943">Subject:</span></b> Re: [Heath] DX-60A Grid Tune Issue<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_ym19_1_1491660371757_13958"><br><div dir="ltr" id="yui_3_16_0_ym19_1_1491660371757_13957">On 7 Apr 2017 at 14:44, Robert Wood wrote:<br clear="none"><br clear="none">> I have a DX-60A that has more than enough drive on 80M and tunes up great - about 75 watts <br clear="none">> out.<br clear="none">> <br clear="none">> Unfortunately 40M thru 10M is QRP. The maximum drive level for 40M is about 2ma, and 20M <br clear="none">> through 10M less than 5ma.<br clear="none"><br clear="none">Hmmmm....6146 requires no more than 2.5 mA grid drive. It sounds to me as though your <br clear="none">driver is providing enough drive. 5mA is WAY too much grid-current for a 6146. If that level of <br clear="none">drive current is held too long, the tube will go "flat".<br clear="none"><br clear="none">> The Final Tune and Final Load controls have little affect on the <br clear="none">> meter in plate position.<br clear="none"><br clear="none">THAT is where the problem lies: in the transmitter output circuitry....at least IMHO. I think you <br clear="none">should be looking carefully at the PA plate circuit, not the driver. Perhaps the low-pass filter is <br clear="none">defective. Try bypassing the low-pass filter then try tuning up. See if that makes any <br clear="none">difference. There should be a sharp plate current dip at resonance. If you don't get one, then <br clear="none">something is not right in the output circuitry.<br clear="none"><br clear="none">> Does anyone know how to adjust L1? I cannot find any information in the manual other than it <br clear="none">> says it is for 40 through 10. I tried adjusting it up and down a little with no change.<br clear="none"><br clear="none">That is meant to be broadly resonant in the center of the 40 meter band. Connect an <br clear="none">oscilloscope probe to pins 2 and/or 9 of V-2, the driver, key the transnitter in CW and while <br clear="none">holding the key down, adjust L-1 for maximum on the scope. I doubt if you will see much <br clear="none">effect, though. The peak should be very broad.<br clear="none"><br clear="none"></div><div dir="ltr" id="yui_3_16_0_ym19_1_1491660371757_13957"><br></div></div> </div> </div> </div></div></body></html>