Toshiba e-studio550 Service Manual page 300

(2) Irruptive current control circuit
This circuit controls the irruptive current flowing into the current regeneration condensers mounted on
the drive circuits for the motors to a certain value. The circuit consists of a posister (PTH1) which
controls the current and FET (Q12) which supplies the current in normal conditions.
Base current is not supplied to Q2 and it becomes OFF after the RADF open/close switch and cover
open/close switch are turned OFF till the cathode voltage of ZD3 reaches the zener voltage. At this
time, both voltages are set by R36 and C107. Q12 is turned OFF correspondingly to supply the current
to PTH1, and the current regeneration condensers are charged.
After the current regenerarion condensers are fully charged and when the cathode voltage of ZD3
exceeds the zener voltage after the time allowance given by C107 and R36, a base current is supplied
to Q2 to turn it ON and Q12 comes ON correspondingly. The current limitation is canceled and the
current flowing in the PTH1 starts to be supplied to Q12.
R66, R67, R68 and R69 are discharge resistors to capture charge stored in the current regeneration
condensers right after either of the RADF open/close switch or cover open/close switch is opened. The
circuit consisted of PTH2 and D1 captures the charge stored in C107 right after either the RADF open/
close switch or the cover open/close switch is opened, and also controls incoming current for
instantaneous opening/closing of the cover.
JUNE 2002 © TOSHIBA TEC 16 - 63 e-STUDIO550/650/810 RADF