[klondike98]

You are checking the resistance value of the carbon composition resistors. They generally tend to drift up to higher resistance value with age. Some folks will replace all of them as a standard practice but many only replace the ones that are greater than 20% above spec. You can often check the value while the resistor is still in the circuit but if there are alternate current pathways you will need to detach one end of the resistor and measure. Occasionally they will fail with a complete open but usually its just a higher value than spec.