Garey, I know you had asked if Ken had done an alignment. I know this is a slightly different box, but in the T4X, there's those trimmer caps accessible on the left hand side of the chassis, I would certainly want to make sure those had been peaked for those two bands.
Chuck, K1OM On Dec 13, 2007 5:46 PM, Garey Barrell <[EMAIL PROTECTED]> wrote: > > Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist > gang > ---------------------------------------------------------------------- > > Ken - > > Ken Bessler wrote: > > Ken Bessler <[EMAIL PROTECTED]> made an utterance to the drakelist gang > > --------------------------------------------------------------------- > >> Are you tuning into a "good" dummy load? > >> > > > > Yes. > > > >> What is the plate current reading on the meter when you have 65W > >> output? Does the meter read about the same plate current as on the > >> other bands, or is it considerably less? > >> > > > > 320ma yeilds 70 watts or so on 10 meters and 20 meters - the differance > > is that I can get more current and power on the lower bands. on 10m, > > 320 ma is all she'll produce. Turning the XMTR GAIN further on 10m has > > no effect. > > > 320 mA of current implies 200W of input power, meaning there is roughly > 130W being dissipated in the final tubes. If this is true, the tube > plates would be red very quickly. > > It would be worthwhile to measure the resistance of each of the 15 ohm > cathode resistors, and then measure the voltage dropped across each one > to see how they are sharing the total current, AND verify the accuracy > of the plate meter. > >> Is the neutralization adjusted correctly? Does the plate current dip > >> coincide with maximum output? Or does maximum output power require that > >> you adjust the PLATE control "out" of the dip? > >> > > > > It almost peaks with the dip - it's real close but if I turn the PLATE > control > > just a hair CCW past the dip point I get another 10%. > > > > > OK, so neutralization is close, but not quite. Are all three tubes the > same brand? Mixing brands can sometimes make neutralization difficult. > > I don't know the condition or age of your finals, but the most likely > problem is soft finals. This is the most common reason for power > dropping off as you go higher in frequency. We'll know a little better > if you can measure the individual currents as above. > >> The final tubes may be getting "soft". Weak final tubes exhibit low > >> output power first on the highest bands. > >> > >> 73, Garey - K4OAH > >> Glen Allen, VA > >> > > ---------------------------------------------------------------------- > Submissions: [EMAIL PROTECTED] > Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body > Hopelessly Lost: [EMAIL PROTECTED] - help in body of message > Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net > ---------------------------------------------------------------------- >
