[Radioroslyn]

My 2c. Tubetesters are a headache because of all of the switching it tough to follow flow of voltages.

R-107 is critical. It determines the amount of current that flows thru the meter. Never operate it with the meter in circuit and R-107 out. Use your decade box connected in parallel w/R-107. Start with a low resistance raising it till you get the meter to behave. Remove the meter from the circuit and measure the resistance of R-107 with the decade box connected. Replace R-107 with resistance just measured. R 104,5,and 6 are fairly critical too. I might take R-107's original value with a grain of salt. It may have had the meter movement replaced which would probably require a different value. Once the meter and the shunt (R-107) are working the other original resistor's values should work ok.

Now if this was a shop fixing this they would have a "test tube". It's a tube that has a known specification so when put into the suspect tester it can be tested to see if it's work properly. I don't know if you have a way of evaluating the accuracy.