Top Cover Open Detect Circuit - Toshiba DP120F Service Manual

3.19 Top Cover Open Detect Circuit

07-03-19
Fig. 7-3-19
The top cover open detect circuit consists of the PTC GA (IC45), A/D converter, and other
peripheral devices. It detects the open or closed status of the top cover by monitoring the
voltage of 24VSW supplied from the LVPS.
24VSW delivered from the LVPS is supplied or cut off by the top cover open switch connected
to CN2 of the LVPS. When the top cover is closed, the top cover open switch is pushed down
by the plate of the top cover and turns on to supply 24VSW to the entire system. When the top
cover is open, the top cover open switch turns off to cut off the delivery of the 24VSW power
supply.
The A/D converter of the Main PBA divides 24VSW supplied from the LVPS, converts it to a
digital value, and outputs the ADCDO signal to the PTC GA. The PTC GA compares the rated
value stored in the internal register with the ADCDO signal (measured value). If the measured
value is higher than the rated value, it will be detected that the top cover is closed. If the
measured value is lower than the rated value, it will be detected that the top cover is open and
the message "TOP COVER OPEN" will be displayed on the LCD of the Operation panel PBA.
DP120F/DP125F Circuit Description 7-52 March 2000 © TOSHIBA TEC