Hopefully, for your sake, the passband tuning unit is not in need of alignment. I doubt very much that bad caps are to blame for your troubles that is unless you can see that some or one of them has broken off a piece. However, there are switch contacts involved in the assembly so there is a possibility that cleaning those contacts may solve the problem. I would not use DeOxit in a spray can, I'd use the other type in a bottle with an applicator. If the passband tuning knob points to the center of the semi circle in the narrow position, that would pretty much confirm the unit is aligned properly. There is some attenuation as you decrease bandwidth due to the reduction in coupling capacitance from each resonating L/C section. Since I'm not home now, I can't say how much. Also check the other positions for the same response as described for the narrow position. For me, it's best to check SSB response for the same pitch or very close to it from lower to upper. If you feel !
lucky,
try following the procedure outlined in the manual. Perhaps the best way to describe the whole process is very touchy. Having done it successfully myself, I can only say it's not something I'd look forward to again!
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From: "Darwin, Keith" <[EMAIL PROTECTED]>
I spent some more time with the R-4A last night. I carefully sprayed DeOxit into the AF & RF gain pots, and the wafer switches; esp the IF bandwidth switch. The rig does work better now. Things are better now.Unfortunately, the IF bandwidth issue is still there. A signal that is S9 in the 3 widest positions drops to about S5 or lower in the .4 position, even when I correct the pass band tuning to peak the signal. Any ideas of what the cause may be? I'm assuming bad caps in the LC IF filter but looking at the jumble of parts around the IF bandwidth wafer switch, I'm not thrilled about trying to replace them.- Keith KD1E -
