Frank - Interesting!
One thing, tuning the RF TUNE to the "middle of the 80M band" _segment_ is probably tuning to the IF of 5.645 MHz.
I certainly suspect Bias supply troubles. Is the FInal idle setting ok at 70 mA? Possibly intermittent loss of Bias which could partially "key" the transmitter.
I would strongly suggest replacing the Bias supply filter caps at a minimum. The chances of catastrophic failure with considerable damage are just too great to ignore.
73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs <www.k4oah.com> iz oos wrote:
Hi Folks, Premise: my AC-4 has still all the original caps, included the bias ones which I should decide to change. Weeks ago, I had experienced something very strange with my T-4XB. It tunes correctly, but, at a particular point of the RF-TUNE in the middle of the 80 meters band, it absorbed 320mA notwithstanding the rig was going to be tuned on completely others band such as the 20meters band with the GAIN control set to minimum!!! This scared me. It happened twice, albeit I was very quick to move the RF tune knob so I saw the 320mA just for less than a second or so. It seems that no apparent damage occurred, as I tuned the rig on the band correctly. But after that day then I haven't turned the rig on again. Could it be due to the bias caps or to something else? 73, Frank IZ2OOOS
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