VT100.net: Digital VT100 User Guide

Table 1-4 Problem Checklist
Symptom	Possible Cause and Corrective Action
VT100 will not turn ON when the power switch is set to ON.	AC power cord is not plugged into wall outlet; plug in cord. AC power cord is not plugged into the terminal; plug in cord. Power is not coming from the wall outlet; check outlet with a known working electrical device (such as a lamp). If no power, call your electrician. AC line fuse blown; turn terminal OFF and have the fuse replaced. (See Figure 1-3 for location).
No keyboard response	Keyboard cable not plugged into monitor; plug in keyboard cable. KBD LOCKED indicator on; computer has turned the keyboard off. The KBD LOCKED conditions may be cleared by entering and exiting the SET-UP mode. If this condition persists, check with the host computer software people for a possible operating error. Perform the self-test operation.
Garbled or Error () Characters	Incorrect SET-UP feature selection; correct the SET-UP features. Suggested SET-UP features which may be in error: ANSI/VT52 mode Auto XON/XOFF Bits per character Parity Parity sense Receiver speed Transmit speed Perform the self-test operation.
Several successive long tones	The terminal has had difficulty in reading or writing the SET-UP features stored in non-volatile memory. Check the feature settings and perform the save operation. Perform the self-test operation.