Service manual

PN 4237242C
2.2-7
INSTRUMENT DESCRIPTION
POWER SUPPLY
2
The white/green wires connected to J1-1 and J1-4 supply -18.5 Vrms to bridge rectifier VR3.
This produces an unregulated -25 Vdc that is regulated using an LM7915CK (U6) regulator
circuit. The output of this regulator circuit is the Linear Power Supply card -15 Vdc output.
The red wire pair connected through J1-3 and J1-6 provide 165 Vrms for the aperture supply
voltages. Bridge rectifier VR1 produces about +240 Vdc from this supply. This +240 V is used
by three circuits. It is regulated to +200 V by one circuit and used for the aperture burn or zap
voltage. A CLEAR APERTURE command from the Sensor Processing Adapter with
Diagnostics (SPAD) card, entering the Linear Power Supply card at J3-8 or J3-10 (these pins
are tied together on the card), enables relay K1, which outputs the zap voltage to the
apertures. The +240 V is also used to produce the Red and White Aperture Voltage circuits.
These circuits receive gain control from the SPAD card, the red aperture current control from
pin J3-6, and the white aperture current control from pin J3-5. Performing the Latex Gain
Adjustment procedure (Heading 4.27) sets this gain.
A RED APERTURE ON command at pin J3-7, and a WHITE APERTURE ON command at
J3-4, both from the SPAD card, direct the output voltages to their respective apertures at the
appropriate time.
Test points for the Linear Power Supply card are summarized in Table 2.2-3, at the end of this
section. Figure 2.2-4 shows the location of the test points, the location and setting of the
jumpers and the location of the input and output connectors.
Figure 2.2-4 Linear Power Supply Card
J5
(RBC and WBC
aperture voltage,
zap voltage out)
J3
(Commands,
+5 V in from
SPAD card)
J2
(Hgb LED
current
supply)
X3
(OFF)
X1
(OFF)
X2
(OFF)
J4
(
+15 Vdc
out)
TP8
TP7
TP6
TP5
TP4
TP3
TP2
TP1
J1
(Transformer
ac input to Linear
Power Supply card)
TP10
(WBC aperture
voltage)
TP9
(RBC aperture
voltage)
TP11
(Zap voltage)
7242004A
C