Tektronix 2236, Instruction Manual

Page: 147 / 350

Maintenance— 2236 Service
Table 6-8 (cont)
Error Code Explanation Possible
“ZZZZ” Cause
F-26 U1100 did not reset after resetting the counter. With each error code (F-26 through F-33)
F-27
U1101A did not reset after resetting the counter. suspect the listed 1C and its associated
tri-state buffer for open or shorted
connections.
F-28 U1102 did not reset after resetting the counter.
F-29 U1103 did not reset after resetting the counter.
F-30 U1200 did not reset after resetting the counter.
F-31 U1101B did not reset after resetting the counter.
F-32
U1201 did not reset after resetting the counter.
F-33 U1202 did not reset after resetting the counter.
F-34 Sample counter did not increment after U1001A was
enabled and clocked in the width mode.
Suspect U1002A and CR1001.
F-35 BUSY line remains HI when both the ENABLE line and
the clock input of U1001A were set LO in the width
mode.
Suspect U1004A.
F-36
The Time counter contents were out of bounds (Time Check the 100 MHz signal line to the time
counter not working correctly after making a trial
counter. If necessary do Test 4 (Extended
measurement on the internal test signal in the width Counter Test) to check out the Time counter.
mode). Check that U1200 toggles at 100 MHz, and
that the level
translators (Q1200 and Q1203) are working
correctly.
Test 3— DMM
This test performs measurements of ground offsets and
reference voltages present in the DMM hardware and is
equivalent to the Power-Up DMM test. When checking a
measurement against upper and lower limits, it is the fre­
quency of the voltage-to-frequency converter that is being
checked. The output frequency of the converter is inversely
proportional to the applied voltage (as the voltage becomes
more positive, the frequency becomes lower).
The DMM test procedure starts by switching the multi­
plexer (U1905) to analog ground and switching U1907A to
divide-by-one mode. For the second measurement, U1907A
is switched to divide-by-five mode. For the third measure­
ment, the multiplexer is switched to the DCV reference volt­
age. For the last measurement, the multiplexer is switched
to the Ohms reference voltage.
To start the test, set the Channel 1 Input Coupling switch
either to GND or DC position. The readout will display
“t3 PASS Y” or “t3 ZZZZ Y” where “ZZZZ” represents
an error code. See Table 6-9 for an explanation of the error
codes.
Test 4— Extended Counter
The Extended Counter test checks the last 11 of the 23
stages of the Sample Counter and performs a more detailed
check of the Time Counter. Before starting the test, move
jumpers PI 000, P1100, and PI 200 from the Norm positions
to the Test positions. With the jumpers in their test posi­
tions, Test 2 and Test 3 test messages become invalid.
The repositioning of PI 000 allows both the Sample and
Time Counters to count the internal test signal. The
repositioning of P1100 and PI 200 divides the Sample and
Time counters into two shorter length counters each. This
increases the testing speed.
6-15