Testing resistors in circuit

[thenewguy]

I am hoping someone could tell me if resistors can be tested while still in the circuit or must they be disconnected at one end, like a capacitor, to remove them from the circuit? I finished recapping a Philco 47-1230 and need to move on to the next step in the troublshooting. I know, I should have tested the resistors as I proceeded with the recap. Won't do that again! I have gone through and tested a dozen or so of the easy to get at ones, just as a experiment, and some test within spec, a few are way off, and one was open. I just don't know if I can trust my readings if the resistors are still connected. Also, of the ones that test out of spec the resistance has gone up, sometimes as much as twice the rating. Is it typical for a bad resistor to increase in ohms, or can they go either way? Are there any good methods for doing this? Thanks

[wa2ise]

For the most part, you can measure resistors in circuit in a tube set (with the power disconnected!) and get readings pretty close to what you'd get out of circuit. In any event, in circuit would make for lower than true readings, but not higher resistance than what it really is. High resistance resistors like 470K and higher tend to go way high when bad. I had 470K resistors go to 870K. Which didn't help in a triode audio driver circuit. Replaced it and that circuit worked again.

[thenewguy]

Thank you wa2ise, I'll keep plugging away at this Philco.