Tektronix DM 5010, Instruction Manual

Page: 242 / 347

Maintenance— DM 5010
3. FRONT-PANEL, Front-Panel Drive board,
Diagram 11
a. If all indicators and push buttons are inoperable,
check J 1820-12 for +5 V and J1820-20 for + 8V.
b. If one or more LEDs do not illuminate, check the asso­
ciated anode driver and the circuit path from the anode driv­
er to the front panel.
c. If the same segment in al! LEDs stays off or on, check
the associated cathode drivers and circuit paths.
d. If only one LED or segment is always off, check that
LED and its circuit paths.
e. If one of the push buttons is inoperable, check the
push button switch and its circuit board paths.
f. If several push buttons are inoperable, check the col­
umn drivers and row lines and their paths between the
Front-Panel Drive and Front-Panel boards.
4. ISOLATED SUPPLIES, Isolation Board,
Diagram 4
If any of these supplies are working, the problem with a
malfunctioning supply is located in the isolated section.
When troubleshooting a supply on the Isolation board, use
an extender board only for the bottom Isolation board con­
nector to the Main Interconnect board; leave the top con­
nector unconnected.
a. Check the following no load supply voltages on the
Isolation board:
b. Check for a 50 V peak-to-peak squarewave (18 µs up
and 18 µs down) between the collectors (cases) of Q1201 or
Q1202 and
ground (TP1421). If the squarewave is not
present, check the 1/2 A fuse.
c. Check for a 1 MHz TTL squarewave at J1733-11B
(Bo2 on diagram 6). If not present, check the circuit back to
U1 230 on the CPU board.
d. Check for a 27.78 kHz TTL squarewave at U1325B-8
and 9 (on diagram 4). If present, check the transistors and
associated components of the transformer drive circuit.
e. Check for a 250 kHz squarewave at U1535B-8 and 9
(diagram 6). If not present, check U1535.
f. Check for a 4 µs pulse every 72 µS at U1730-15. If not
present, check the -e-18 circuit (U1635B, U1730, U1635C,
U1530B, U1320B).
NOTE
A blown fuse may indicate an overload in another cir­
cuit. To troubleshoot an overload condition, it may be
helpful to temporarily replace the fuse with a 75 to
200 Ω, 3 W resistor. After troubleshooting, be sure to
reinstall the fuse.
5. FUNCTION & RANGE REGISTER
To troubleshoot this circuit, do the following steps or use
a signature analyzer to check the signatures in Table 10B in
the pullout pages. For the following steps, use an oscillo­
scope; connect the external trigger (- slope) to U1520-7 on
the CPU board, diagram 7. Set the DM 5010 to the fast
conversion rate. Set the oscilloscope to 5 V/cm and
2 ms/cm.
Table 7-4
NO LOAD POWER SUPPLY VOLTAGES
+ lead — lead Voltage Limits (V de)
P1701-15B P1701-15A + 9,2 V to+11.6 V
-14B -4A or 4B
+ 16.6 V to +20.8 V
-14A -4A or 4B
-20.8 V to -16.6 V
-13B -4A or 4B + 33.3 V to+41.7 V
-13A -4A or 4B • -41.7 V to-33.3 V
-7A ’
-7B
I +33.3 V to+41.7 V
If any of these voltages are outside the limits, check the
associated rectifiers and filter capacitors.
a. Check RC at J1731-10B. Look for a closely grouped
set of 32 pulses; then check for a second group of 32
pulses, not as closely or as evenly spaced as the first group.
Note the position of the last pulse. Then check RD at J1731 -
9B. It should have a fixed bit pattern only during the second
pulse group checked previously. Change the DM5010
range or function and check that the bit pattern changes.
The RD line also has a short pulse just following the last RC
pulse.. Also check RC and RD on the Main Interconnect
board (diagram 10) and at the opto-isolators, U1515-3 and
U1610-3 (diagram 5). Change the oscilloscope ground refer­
ence to
PGND (P1701-4A or 4B, diagram 5), and position
the trace near the top of the crt display. Check IRC and IRD
at U1 515-6 and U1610-6, and on diagram 10 at J1701 -11A
and 11B.
7-12 ADD JAN 1982