Welch Allyn Atlas Service Manual page 101

5.3.1 Horizontal Gain:
Horizontal deflection is adjusted by changing the current through the Horizontal coil. Changing the series
inductance in the Horizontal Deflection Path modifies the current. Increasing Horizontal gain is then
accomplished by writing a pattern to the CRT, and adjusting the "width coil", L3.
Horizontal Centering:
Horizontal centering is accomplished by rotating magnets mounted on the CRT Yoke assembly.
5.3.2 Grid Voltages:
The following voltages are developed to bias the grids on the CRT:
Grid 1: -10V to -50V DC (Brightness Adjust)
Grid 2: 350VDC
Grid 4: 0V to 350VDC (Focus Adjust)
Anode: 7.5KV
These voltages are derived from additional windings on the FBT. In addition, the supply voltage for the
video amplifier (+36VDC) is generated from a tap on the FBT.
+12V
Horizontal Sync
5.5uSec
31.7uSec
+12V
R24
10K
C22 R25
U4B
.022uF 215
3 4 C22-2
Hsync
R50
74HCT04
1.96K
Appendix A
Boost
C11
+
1000uF
D2
L1
+B
+12filt 1 2
47uH
MUR120
+
C10 Hor
1000uF
+12V
R26
1K
R27 Q6
10 IRF640
q5.c q6.d 1
3
q5.b 2 Q5
1 2N3904
To CRT
T1
Anode
CRT-FBT
Horizontal Amplifier
Grid Voltages
9
8 D3
1N4935
10 2 Vd 1 2
+
7 5
D4
1N4935
3 Vg1 2 1
1 Vg2
D5
1N4937
1 2
C9
6.8uF
hlin hwide
C8 L2
.022uF 15uH
10/14/99
Grid1
+Vvid Intensity
C15
C12 .01uF
22uF
R29 100K
R28
Brightness 19.6K
Adjust
d4.a
C13
R30
22uF
100K
C16
.01uF
d5.c
C14
.01uF Focus
R32
Adjust
2.5Meg
C17
.01uF
L3
15- 35uH
L
Horizontal Yoke
Grid 2
Focus