Tektronix 2246 1Y, Service Manual

Page: 147 / 433

Maintenance—2246 1Y and 2246 Mod A Service
NOTE
Use 20 MHz bandwidth limiting on the test
oscilloscope. A higher bandwidth may pro­
duce higher observed ripple levels.
If the power-supply voltages and ripple are within
the listed ranges in Table 6-4, the supply can be
assumed to be working correctly. If they are outside
the range, the supply may be either misadjusted,
operating incorrectly, or excessively loaded. The
power supply adjustment procedure is given in the
Power Supply, Display, and Z-Axis subsection of
Section 5 (the Adjustment Procedure).
A defective component elsewhere in the instrument
can create the appearance of a power-supply prob­
lem and may also affect the operation of other
circuits.
Use the power distribution diagrams
(schematic Diagrams 14 and 15 in the foldouts) to
aid in localizing a loading problem to a particular
circuit.
9. Check Circuit Board Interconnections
After the trouble has been isolated to a particular
circuit, again check for loose or broken con­
nections, improperly seated semiconductors, and
heat-dam aged components.
10. Check Voltages and W aveform s
Often the defective component can be located by
checking circuit voltages or waveforms. Typical
voltages are listed on the schematic diagrams.
Waveforms indicated on the schematic diagrams by
hexagonal-outlined numbers are shown adjacent to
the diagrams. Waveform test points are shown in
the circuit board illustrations.
NOTE
Voltages and waveforms indicated on the
schematic diagrams are not absolute and
may vary slightly between instruments. To
establish operating conditions similar to
those used to obtain these readings, see the
Voltage and Waveform Setup Conditions pre­
ceding the waveform illustrations in the
Diagrams section.
Note the recommended test equipment, front-panel
control settings, voltage and waveform conditions,
and cable-connection instructions. Any special con­
trol settings required to obtain a given waveform are
noted under the waveform illustration. Volts/Div and
Sec/Div settings of the test oscilloscope for a
waveform are indicated in the waveform illustration.
Table 6-4
Power Supply Voltage and Ripple Lim its
Nominal
Supply
Voltage
Test Point
(+ lead)
Test Point
(+ lead)
Lim its (-10°C
to 55°C)
P-P Ripple a
Min Max 60-150 Hz
20-40 kHz
+130 J1204-11
+ 127 +135 70 mV
70 mV
+58
J1204-10 +55 +59 40 mV
120 mV
+15 J 1204-7 + 14.6 + 15.6
8 mV 4 mV
+7.5 J1204-8 +7.4
+7.6 8 mV 4 mV
+5.0 J1204-1,2 +5.0
+5.3 30 mV 20 mV
-5 .0
J 1204-5 -5 .2 -5 .4 4 mV 4 mV
-7 .5 J1204-9
-7 .5 -7 .8 4 mV 4 mV
-1 5 unreg
J1204-6 -15.5 -16.6 10 mV
100 mV
aA t ra te d load.
6-8