Sonics E-Series - Manual (Page 12)

19) Check R26. It should read approximately 100 ohms. If not, replace it (Part no. 867-00124).
20) Check R30. It should read approximately 400 ohms. If not, replace it (Part no. 867-00196).
21) Check R31. It should read approximately 400 ohms. If not, replace it (Part no. 867-00196).