General radio Co. Type 631-BL Strobotac Operating & Maintenance Instructions
Form 394-V, June 1957
Contents: Operating Instructions
1.0: Purpose
2.0: Description
3.0: Operation
4.0: Use
5.0: Extension of Range
6.0: Additional Suggestions
7.0: Maintenance
Contents: Service & Maintenance Instructions
1.0: Foreword
2.0: General
3.0: Strobotac Inoperative
4.0: Dial Lamp Does Not Light
5.0: Reed will not Vibrate
6.0: Strobotac Blows Fuses
7.0: Dial Lamp Burns Dimly, Strobotac Draws Excessive Power
8.0: Strobotron Tube, V-3, Flashes Erratically
9.0: Indicating Flashing Speed Differs by More Than One Percent Between High & Low Scales
10.0: 3600 RPM Cannot be Set by 3600 Adjust Trimmer
11.0: 900 RPM Cannot be Set by 900 Adjust Trimmer
12.0: Strobotac will not Calibrate Properly
13.0: Main Speed Control Knob Binds
14.0: Main Speed Control Knob Has Backlash
15.0: Vacuum Tube Data
Manual is an original.