[R-390] Alignment - Gord Hayward Question

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Fri, 07 Mar 2003 14:04:53 -0500


Of the three questions, T207 is the simplest to align. Set the Megacycle control to any frequency below 8 MHz. Put an RF probe (or a scope probe) on the cathode of V202 and peak L403 for maximum output at the 17.00 MHz crystal frequency.

T401 is a different story because L234 has to resonate over the complete range of frequencies from 11.0 MHz to 34.0 MHz with only the values of the shunt capacitors switched from band to band. The simplest answer is if each of the trimmer capacitors peaks the output signal don't fool with it. The only time it has to be adjusted is if one or more of the trimmers has to be set to maximum or minimum capacitance to get a peak. (In other words, the screwdriver slot of the ceramic trimmers should NOT be perpendicular to the front panel.) Ideally, the slug of L234 should be set so all the trimmers are somewhere around mid-range when adjusted for peak output.
TH-5820-358-35 sort of buries the procedure for adjusting the antenna balance trimmers in paragraph 122 on page 164. I connect a 62 ohm carbon resistor from each side of the balanced antenna jack to the hot lead of a signal generator that has been terminated with a 125 ohm load. Follow the procedure in subparagraphs "a" thru "e" and "g" of paragraph 122. Adjust the "BAL" TRIMMERS C201A, C205A, C209A, C213A, C217A, and C221A for MINIMUM indication of the meter collected to the DIODE LOAD terminal with the front panel ANT TRIM knob peaked.