MFJ-259B FineTune Modification: A shortcoming I noted with the Analyzer, is the lack of a 'finetune', in addition to the OEM course TUNE. It's
disappointing such a capability wasn't designed into the unit. I really found it aggravating that the slightest movement of the TUNE control resulted in a
substantial change, in the indicated parameters. Since I lack the engineering expertise to redesign the circuitry, by adding a 10-turn adjustment, in series/
parallel with the existing control. I got to thinking there might be an alternate method, of acheiving the same basic outcome. My mod is simple, frugal
[read cheap], eliminates the sloppiness; helping to establish the 'feel' of a quality control. You may already have the necessary 7/16" OD x
5/16" ID grommet ( I used a Noble 1124D rubber [?] grommet, normally used to prevent chafing of wires passing through a metal panel) in your parts bins.
Your meter may require a different size, easily determined by measuring. Loosen the TUNE knobs' hexhead setscrew. Remove the knob. Place the
grommet onto the shaft [With a little care, I was able to position the grommet groove as normal.}. Replace the knob, but press downward to compress
the grommet, between the panel and the bottom of the knob. (individual choice, on amount of turning friction required. Less compression/less friction.
More compression/more friction.) Maintain compression, and retighten the setscrew. Mod completed. I was satisfied with the result. With the grommet,
the friction helps prevent dust/dirt intrusion into the unit. This mod may be applicable to the later MFJ-269. Article also posted elsewhere.