Toshiba DP120F, Service Manual

Page: 409 / 706

DP120F/DP125F Circuit Description 7-100 March 2000 © TOSHIBA TEC
8. HVPS
This section describes the functions of the HVPS.
Fig. 7-8-1
07-08-00
The HVPS generates stable high voltage and current from 24VSW supplied from the LVPS and
delivers it to the main charger, discharger, development roller, drum, transfer charger and grid.
It is connected to CN2 on the Mother PBA.
To supply constant-voltage to the main charger and discharger, the I/OP-2 GA (IC48) on the
Main PBA causes the CHVON signal to be HIGH. Then Q1 on the HVPS turns on to supply
24VSW to IC1. IC1 causes Q2 to perform an on/off operation and repeat supplying and cutting
off of current to the primary circuit of the transformer (T1). This allows power to be emitted from
the secondary circuit of the transformer and constant-voltage to be supplied to the main charger
and discharger.
To supply constant-voltage to the development roller, the I/OP-2 GA causes the DEVON signal
to be HIGH. Then Q3 on the HVPS turns on to supply 24VSW to IC2. IC2 causes Q4 to turn
on and off and repeat supplying and cutting off of current to the primary circuit of the trans-
former (T2). This allows power to be emitted from the secondary circuit of the transformer and
constant-voltage to be supplied to the development roller.