[David]

Resistor tolerance is +or- so on the 51K plus 10% equals 56.1K minus 10% equals 45.9K. If I have to remove one end of a resistor to measure its value no matter the reading I will replace, because of possible damaged caused my me!!! On your 49k measure your 47K if the reading is between 44.1K-51.7K will work just fine. The 44.1K is 49K minus 10% the, 51.7 is 47K plus 10% the reason for not using 53.9K if that was the reading from the 47K it would be out of 10% tolerance range. When working on old radios I replace resistoes that are out more than 10% even if the orginals allowed +- 20%. They are cheap and only want to fix them one time. Some radios you will replace most others very few. Hope this helps David