SLE SLE2000 HFO, Service Manual, Page: 13 / 84

SLE2000 HFO Service Manual
Doc No. SM/0001: Issue 7.0
Page 13 of 84
3.1.7 M
OTOR
D
RIVE
B
OARD
A
SSEMBLY
(A0739/01)
3.1.7.1 Motor Drive Circuit
U3 is an RC4152 which produces a motor drive frequency proportional to the HFO rate control voltage.
This is used as the clock input to the stepper motor controller L297 (U1) which in conjunction with the
L298N (U2) provides 4 outputs to drive the HFO stepper motor. This circuit is operative in all HFO
modes.
3.1.7.2 LCD Backlight Inverter
This device provides a high voltage a.c. supply to the cold cathode LCD backlight. It is driven by a 12V
d.c. supply.
3.1.7.3 Miscellaneous
Also located on this PCB are the fresh gas solenoid MOS driver (MOS1) and associated components and
a back E.M.F. diode for solenoid SV3.
3.1.8 P
OWER
S
UPPLY
U
NIT
The power supply unit is a universal AC input switcher type. It has an overall power rating of 80W and is
capable of operating down to zero load. It has overvoltage protection on the +5V line which will shut the
unit down. It typically has a hold up time of 75ms.
The pin connections to the unit are as follows;
Plug J1 Description Output Current
1 Ground
2 Neutral
3 Live
Plug J2
1,2,3 +5.12V 8A max, 0A min
4,5,6,7 0V
8,9 +12V 4.5A max, 0A min
10 Power Fail Detect
11 -12V 0.5A max, 0A min
12 key
13 +24V 3.5A max, 0A min
This unit is not servicable.