I would like to replace this resistor, but its color bands are faded. Does anyone know what resistor I should get for R31?
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up.Sign up to join this community
If the resistor is still OK, though faded, you could measure its value. If it has failed, then you pretty much have to find a schematic with values, or another (identical board) where the resistor is still readable.
Assuming the resistor is OK:
Given how over heated that resistor looks, I'd be afraid of it falling apart if I tried to unsolder it completely.
What I'd do it use a pair of side cutters to clip the lead on one end, then raise it just a little so that the connection is open. Then I'd use a multimeter to measure the resistance.
Clip the lead right at the through hole. Be careful when you clip it not to wiggle the part around too much.
If you don't have a small pair of side cutters, you might use a pair of toe nail clippers (the clippers, not the nail scissors.)
In any case, clip the lead flush to the board.
Once you have the value, push the resistor back down so the leg makes contact with the clipped spot, then solder the leg back together. That lets your circuit keep working until you get a replacement.
Keep in mind the power rating. Under no circumstances should you use a resistor with a lower power rating. Use a higher power rating if you have room for it and can make it fit. The one you have seems to be a little on the small side (power rating wise,) so a higher rating would be a good thing.
Measuring it is your best bet, if it does not work (because the resistor is fried, for example);
Given how old your circuit looks, there is a good chance the schematics are available somewhere online. (I've worked on old valve radios that even had them neatly stored inside the enclosure!);
Depending on the rest of the circuit, R31 could be part of a building block replicated somewhere else on the board (Look for R21, R41, R131,etc.);
As a last resort, deduction time!