[drakelist] R-4B Passband tuning alignment

[Chris Codella]

I recently went through the alignment procedure in the R-4B manual completely.  Turned out my R4-B wasn't too far out.  But the passband tuning isn't quite right - sounds unsymmetrical and a bit leakier that I think it should be.  But I have questions about this part of the alignment procedure as it's the only part I had trouble with.

There are, it seems, 5 adjustments in the back of the passband tuning unit: the 4 individual slugs and the center screw.  The screw is no problem.  But the manual (p.34) isn't very descriptive about how one goes about adjusting the 4 slugs.  It just says to adjust them for maximum negative voltage on TP-2.  Can anyone here shed some light on this?

The slug ends that stick out the back seem to be tightly coiled springs with flattened tips.  When I attempt to turn them with pointed tip pliers, the spring shafts just coil or uncoil and the slug doesn't actually turn.  Is there some trick to this?  A special tool maybe?  The manual does warn about it, saying: "These slugs have a tendency to spring back after being turned, so care must be exercised to be sure the settings giving maximum voltage is made."  Not much help when the slugs don't seem to actually turn at all.

Thanks,
Chris, W2PA