HP FAX-750 Service Manual - Page 164

2.4 Troubleshooting Procedures [ 1 ] Control panel related Trouble (1) LCD shows nothing. (2) Control panel inoperative. Check: • Panel-main harness between the main PCB and the control PCB • Interfaces between the main PCB, NCU PCB and power supply PCB • LCD • Control panel PCB • Power supply PCB • Main PCB • Panel-main harness between the main PCB and the control PCB • Interfaces between the main PCB, NCU PCB and power supply PCB • Control panel PCB • FPC key • Main PCB [ 2 ] Telephone related Trouble (1) No phone call can be made. (2) Speed dialing or one-touch dialing will not work. (3) Speaker silent during on-hook dialing. (4) Dial does not switch between tone and pulse. (5) Telephone does not ring. Check: • FPC key • Control panel PCB by using the maintenance-mode function code 13. If any defective keys are found, replace them. (Refer to Chapter V, Section 3.7, "Operational Check of Control Panel PCB.") • NCU PCB • Main PCB • Ordinary dialing function (other than the speed and one-touch dialing) If it works normally, check the main PCB; if not, refer to item (1) above. • Ordinary dialing function (Pick up the handset and press the numerical keys.) If it works normally, proceed to the following checks; if not, refer to item (1) above. • Main PCB • Speaker • NCU PCB • Main PCB VI - 13