CTX CMS-3435 - Vertical Deflection Circuit; CRT Bias Circuit; Monitor Adjustments; Power Supply Adjustments

ADJUSTMENTS
3.5 Vertical Deflection Circuit Monitor adjustments contained in this section
should be followed whenever a major component is
replaced, such as a CRT / YOKE assembly ora circuit
board. Some adjustments may also be required pe-
riodically to correct for component aging. Adjust-
ments should be performed in specific order given in
The vertical sync pulse from Pin 6 of IC 405 is
sent to Pin 19 of IC301(LA7850) to trigger the
vertical oscillator to be synchronous with the
input sync. The synchronized vertical sawtooth
signal is then taken from Pin 16 to Pin 2 of vertical
output amplifier 1C201 (LM7837). 1C201 con- the following paragraphs.
tains its own driver functions, so the AC / DC 1. Power Supply Circuit
feedback loop can be implemented on this (1) VR101 +95V Adjustment
single IC, problems with crosstalk from the (2) VR102 Def. B+ Limit Adjustment
horizontal signal affecting interlace charac- (3) VR103. +6V Adjustment
teristic is reduced. The DC feedback is sent to
Pin 7 through VR206, R243 and VR203, AC feed- 2. Horizontal Deflection Circuit
back is also sent to Pin 7 through VR205, R243. (1) VR301 H-Center Adjustment 1
Adjusting VR205 and VR 206 can achieve best (2) VR302 ~H-Hold Adjustment 1
linearity, VR203 determines the DC bias point of (3) VR303 +16V Adjustment
the output amplifier. Voltage setting on Pin 4 will (4) VR304 Horizontal Frequency Voltage
determine the sawtooth peak level of the Ramp Conversion Adjustment
generator circuit, thus can be used to adjust for (5) VR305 ~~ H-Center Adjustment 3
vertical size control. Q201, Q214 — Q219 and (6) VR3806 ~H-Center Adjustment 2
their peripherals serves as vertical auto sizing (7) VR307 ~—_H-Hold Adjustment 2
circuit to maintain same vertical size when (8) VR308 —H-Center User Control
changing among 350 / 400 / 480 lines resolutions (9) VR309 X-Ray Protector
according to IBM VGA conventions. VR201 is (10) VR310 High Voltage Adjustment
user vertical size control and VR202 determines (11) VR311. H-Center Adjustment 4
the suitable contro! range for VR201. (12) L305 H-Width Adjustment
4. CRT Bias Circuit 3. Vertical Deflection Circuit
The DC bias voltages for R, G, B CRT cathods (13) VR201 —-V-Size User Control
are supplied by Q213, Q206 and Q207. Q208, (14) VR202 \V-Subheight Adjustment
Q209 and Q210 control the DC level of each gun (15) VR203 V-Bias Adjustment
by adjusting VR211, VR212 and VR213. Q212is (16) VR204 Side-Pin Adjustment 1
for brightness control, it solely controls the DC (17) VR205 = ~‘V-Linear Adjustment 1
levels of all three guns. VR214, VR215 and (18) VR206 V-Linear Adjustment 2
VR216 are sub-bright controls to achieve precise (19) VR207 Side-Pin Adjustment 2
gray background over the entire range of bright- (20) VR208 ‘Vertical Frequency Voltage
ness control. Conversion Adjustment
(21) VR218 V-Hold Adjustment
4. Video Circuit
(22) VR211 R Bias Adjustment
(23) VR212 G Bias Adjustment
(24) VR213 __B Bias Adjustment
(25) VR214 —-R Subbright Adjustment
(26) VR215 GSubbright Adjustment
(27) VR216 ~—_B Subbright Adjustment
(28) VR401 User contrast control
(29) VR501 R Subcontrast Adjustment
(30) VR502 G Subcontrast Adjustment
(31) VR503. ~—B Subcontrast Adjustment
(32) VR504 Subcontrast
For quick reference, page 21 shows the locations
of all adjustments.
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