OFA 9910 = One for all 9910. Radio shack and One for all should have the same base station as Edmund wrote. But, on my base station, R24 was 220K instead of 330K. I found that R23 was 330K, so I removed R23 and changed it for a variable resistor of 0- 500K. There is a little screw on it that let me set the resistor from 0 to 500K. After playing with the resistor a bit, the problem has gone. When I bought the variable resistor, I also bought 220K, 330K and a 910K. I have tried the 220K in R23 but it has not worked. It is pretty easy to remove the resistor that is already there, so you can try it if you have a resistor near 240K.