Tektronix DM 5010, Instruction Manual

Page: 243 / 347

Maintenance — DM 5010
Next, check the STROBE signal on the ADC and RMS
boards at shift registers U1500-1, diagram 2, and U1330-1,
diagram 3, respectively. The strobe should appear only dur­
ing the short pulse at the end of the RD pulse train. Check
the input and output (pins 2 and 9) of each register.
If the shift registers are working and a range problem still
exists, check the latches and the switches they drive for the
malfunction. Refer to Figs. 10-2 and 10-5 in the pullout
pages.
6. A/D CONVERTER, Isolation Board, Diagram 5
First determine whether the problem is in the isolated or
grounded parts of the A/D Converter. To do this, place the
Isolation board on one extender, leaving the top board con­
nector unconnected. Jumper U1710-3 (U/D) to U1510-6
(COMP) on the Isolation board. Check the display with U/D
jumpered to COMP, an overrange negative voltage indi­
cates the fault is in the isolated circuit; a displayed error
code 311 suggests the fault is in the grounded circuit. Re­
move the jumper between U/D and COMP, and check the
indicated circuit.
a. Isolated A/D Circuit: If the problem is in the isolated
section, refer to the sections in the DC Voltage Measuring
Circuit Troubleshooting section dealing with 311 errors and
the Charge-Balancing Converter.
b. Grounded A/D Circuit: Check the path of the TRIG
pulse through the control ICs at the following points:
U1530A-6 (In Progress)
U1435C-8
U1425A-5
(M/2)
U1435A-3
U1330A-5 (Override)
U1230A-5
U1420C-8
U1425B-8
parallel representation of the counters inputs from U1020,
U1120, U122Q, and U1130. Trigger the oscilloscope on
U1425A-5, M/2, diagram 5; then check that the UP and
DOWN pulses beginning at U1020-5 and 4 propagate
through the counter ICs and that their outputs toggle appro­
priately. Check that the counter is reset to 0 by the RS
pulse, U1020-11.
7. DC VOLTAGE MEASURING CIRCUITS, ADC
Board, Diagrams 1, 2
a. To check the supply voltages to this circuit, place the
ADC board on an extender board and measure the voltages
listed in Table 7-5.
Table 7-5
POWER SUPPLY AND REFERENCE VOLTAGES
Measurement
Location Diagram Voltage Limits
U1230-16
1
+ 11.4Vto +12.6 V
U 1230-6 -12.6 V to -11.4V
VR1321-C + 6.28 V to +6.42 V
VR1223-C + 21.5 V to +22.5 V
VR1225-A -22.5 V to -21.5 V
VR1001-C + 32.5 V to +41.7 V
VR1013-A
-41.7 V to — 32.5 V
U1400-14
2 typically — 22 V
U1 400-7 -27.5 V to -26.5 V
VR1501-C +4.8 V to +5.4 V
If the voltages are correct, continue troubleshooting at
part 7b.
If these voltages are incorrect, remove the RMS board
from the plug-in and remove the ADC board from the ex­
tender board. Measure the voltages in Table 7-6, on tne
extender board connector. The measurement locations are
the Main Interconnect board connector pin numbers.
Check U1330B-8 (U/D) and U1335B-10 (COMP). COMP
should follow U/D.
On diagram 6, check U1635A-12 (EOC) and U1520A-3
(EOAZ). Check Q1 through Q12 of U1525 for a squarewave
signal; each signal should be one-half the frequency of the
preceding signal.
To check the data generation, trigger the oscilloscope on
TP1625, Stop, on diagram 7; then check that U1235-15 and
U1320A-6 count out the 17 Advance pulses (diagram 6).
Check U1030B-6 (DATA) for a serial representation of the
17 bit input to U1125 and U1030C-8. Check U1125-10 for a
T
Table 7-6
NO LOAD POWER SUPPLY VOLTAGES
Measurement
Location
Voltage Limits
(+ lead) (- lead)
15B
15A
+ 9.2 V to +11.6 V
14B
6B
+ 16.6Vto +20.8V
14A
6B
-20.8 V to -16.6 V
13B
6B
+ 33.3 V to +41.7 V
13A
6B
-41.7 V to — 33.3 V
ADD JAN 1982 7-13