Section V Model 175A
Paragraphs 5-93 to 5-100
m, de 5-8 Horizonta Amplifier Troubleshooting
Procedure Effect Trouble
Connect DC Voltmeter to pin 2 of V204. 0 volt reading impossible R262 or V203
Adjust HORIZONTAL POSITION for
reading of 0 volt. Correct reading Input circuitry good
Measure voltages at pin 1 of V204 and Voltages unequal V204 or V205
Voltages approx equal pin 1 of V205. V204 and V205 good
Measure voltages at pins 3 and 8 of V208. Voltages unequal V208 or V209
Voltages approx equal V208 and V209 good
5- 93. HORIZONTAL AMPLIFIER. a. Remove top cover of instrument.
5-94. Signal waveforms and their associated dc levels
are given as a troubleshooting aid on the horizontal- b. Remove all leads connected to neck of crt (see
figure 5-12).
amplifier schematic diagram, figure 5-28.
5-95. If the horizontal amplifier appears to operate
c. Remove post accelerator cap from crt (located
properly with the HORIZONTAL DISPLAY in any of near front of crt case).
the external input positions, but not in internal sweep
positions, the trouble is most likely in the sweep
generator. d. Carefully remove bakelite plug from base of crt.
5-96. If the horizontal amplifier appears to operate
properly with the HORIZONTAL DISPLAY in the
internal sweep positions, but not in any of the external e. Remove screws from clamp at base of crt and
input positions, the trouble is most likely associated remove top half of clamp. If necessary loosen bottom
half of clamp.
with the horizontal input amplifier.
5-97. UNBALANCE. The cause of unbalance in the
horizontal amplifier will most likely be associated f. Remove front panel crt bezel.
with V204, V205, V208, or V209 since these are the
only stages connected in the differential configuration. g. Carefully slide crt out through frcnt panel hole.
Measurement of dc voltages on each side of the
amplifier is the best method to use to isolate the Light mask removes with crt.
cause of unbalance because of the feedbackused in the
amplifier. Proceed as in table 5-8.
h. Installation of replacement crt is essentially
5-98. GAIN. If the amplifier has the wrong gain the reverse of removal procedure described above.
ensure that it cannot be corrected by adjusting Gain Refer to figure 5-2 for correct connection of deflec-
Adj R213, X1 Gain Adj R225, or X10 Gain Adj R227. tion leads. Do not over-tighten base clamp or tube
The waveforms given on the schematic diagram, fig- may be damaged. Before tightening clamp, rotate
ure 5-28, provide information on the gain of each crt until bottom of graticule is parallel with bottom
stage. Start at the input and proceed toward the of front panel and be sure light mask just touches
deflection plates. bezel.
5-99. CATHODE RAY TUBE REPLACEMENT. i. Obtain a free running trace and adjust TRACE
ALIGNMENT until trace is aligned with horizontal
5-100. To replace the crt in the Model 175A,proceed
as follows: lines of graticule.
WARNING
To prevent injury to eyes and hands if crt j. Make checks and adjustments, if necessary,
breaks, wear plastic face mask or goggles referred t.0 in the following paragraphs in the order
and insulated gloves. Handle the crt with given: 5-37 through 5-39, 5-42 through 5-46, 5-51,
extreme care. 5-52, and 5-55 through 5-57.
5-18 01526-2 |
ACEC
