If you know the value of the pots, you can just measure at the jack of a passive bass and use the following formula to get the pickup's DCR: R1=1/([1/RTotal]-[1/R2]), where R1 is the resistance of the pickup, R2 is the resistance of the pot(s), and RTotal is the resistance at the jack. If there are multiple volume pots or a blend pot in the circuit, be sure the pickup selection is set to solo the pickup in question, and then account for the total resistance of the pots as: RTotal=1/([1/R1]+[1/R2]+...[1/Rn]), where R1 is the first pot, R2 is the second, and so on. Be sure to account for variations in pot tolerances as you average out a resistance, however. Tolerances are often 20% for pots. Or, simply desolder the pickup and measure it.
Note that DCR probably won't tell you anything. It is very unlikely for pickups to develop internal shorts, and once wound, the number of winds doesn't change. DCR will change if there are differences in the temperature of the coil, but it will not be significant to change the output impedance. DCR bears no inherent relation to output anyway.
Last edited by line6man : 12-20-2012 at 04:29 PM.