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1220freqjump [2007/05/20 19:40] (current)
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 +====== Model 1220 Frequency Jump Fix ======
 +**From the Ten-Tec Reflector January 4, 2003**
  
 +While visiting Ten-Tec a while back, I mentioned the above problem and was given a "​Fix",​ which works for me on the 1220 and the 1230, 220 MHz Version, as well.
 +
 +Just add (Solder) an Electrolytic Capacitor, from about 1uF to 4.7 uF, 15VDC or more, across Resistor ​ R32 (In parallel). ​ The Positive end of the Capacitor goes toward the Base of Q8, the 2N4124 Transistor. This is the side of R32 away from the Front Panel.
 +
 +Evidently, when you let up on the PTT switch, the supply voltage jumps, causing a power-on reset to the microprocessor. ​ The processor then retains the old transmit frequency as the current receive frequency. ​ Ten-Tec suggests several ways to try to correct this problem, including using heavier wire from the power supply and shorter lengths, to prevent voltage drops, and also adding a capacitor in the space labeled C86, on the PC Board. ​ This capacitor should be an Electrolytic in the range of 1,000 to
 +4,700uF, rated at least 16VDC or more.  The Positive end should be oriented as shown on the PC Board. ​ You may have to look around for a capacitor small enough to fit on the space available on the board. ​ I had to use one with both leads coming out the bottom, and adding a piece of wire and insulation, to get a cap small enough to fit in the space.
 +
 +I found that adding the capacitor across R32 is what cured the problem for me. Adding C86 helped when the rig was used in mobile operation.
 +
 +Carl Morris, WN3DUG

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