Samsung SF-4500 Service Manual page 47

• +22V Power Controller
If you insert power cords, the main board will be
supplied with power. /POR signal put out through
reset circuit activates MFP controller
(K32C6200:U16) and MFP controller puts out exter-
nal circuit reset signal /RST-OUT. This /
RST-OUT signal and Vrefx (+2.5V) divided through
+30V are impressed to the input
terminal of the comparator, putting out +22V if the
output of the comparator is "high" or getting
turned off if "low".(in case of /FAULT-TEST
signal: HIGH) While +22V is being impressed after
/RST-OUT is "High", comparator output gets
"low" and turns off +22V driving TR(TIP112) if
/FAULT-TEST signal is put out at "low" when you
check a short of the head driver and the ink car-
tridge (head).
• FAULT TEST CIRCUIT
This is a signal to detect whether the head
receiving the output of head column driver is in a
short. After /FAULT-TEST signal is put out at
"low" and +22V is turned "off", "OK2PRINT"
signal is entered. The port of KS32C6200(U16)
shows normal condition if "H" and a short if "L".
If you make FAULT-TEST output "L" to detect
fault of the head, +22V gets off. If the head is in a
short (LOW), when the level of "/FAULT-TEST"
Mono Head
70°C
35°C
6-16
Pre-Heat if below 35°c
Fig.6-1-13. Temperature around Mono Head
signal goes "L" and final "OK2PRINT" output
goes "L". KS32C6200(U16) reads this signal and
checks whether the head input receiving the
driver output is in a short. Diode cathode is
attached to each output transistor collector in the
column driver. 8 anode terminals of diode become
common as one and put out /FAULT signal, which
is pulled up by bias circuit controlled by /FAULT-
TEST and shows the condition by OK2PRINT
through the comparator.
• SUBSTRATE HEAT CIRCUIT
Mono ink cartridge of Babbage head is 600dpi head
that uses pigment ink. It is very sensitive to the
temperature in and around the cartridge. In
particular, the viscosity of ink affects print quality
as it is inversely proportional to temperature by an
exponential function. This signal used to
compensate it helps you get equal inking quality
by warming the ink chamber in the cartridge with
aluminum pattern heater before starting to print if
the surrounding temperature is lower than
standard (below 35°...).(Refer to Timing Chart.) It
sends PRE-HEAT signal through I/O port of
SCANIP(Color Image Processor:U18) and supplies
+11.75V.
Samsung Electronics