Table of Contents
Advertisement
Model 11713A
Service
TROUBLESHOOTING
The Driver circuits are conventional and straight
forward.
Significant circuit stage
functions are
identified on the schematic diagrams. Use the infor¬
mation on the schematics and the procedure in
Table 8-1 to isolate a malfunction.
Table 8-1. Troubleshooting Hints
1.
Remove the Driver top cover.
2.
Turn on the Driver and verify that the proper power up status is reached. The Driver comes up in
local with all pushbutton LED's on which corresponds to maximum attenuation settings.
3.
Measure the voltages at AlTPl and A1TP2.
TPl = +5.0 ±0.5 Vdc
TP2 = +24.0+1.0 Vdc
4.
Verify that the +24.0 ±1.0 Vdc is present at the rear panel red banana jack.
5.
If an attenuator or switch buzzes when actuated by the front panel pushbutton, the output transistor
may be shorted, or one of the protection diodes may be shorted.
6.
If one of the pushbutton LED's does not light. First determine if the pushbutton is operational by
checking to see if the clrcuitry^drives an attenuator or switch properly. If the switching click of the .
relay in the attenuator or switch can be heard, this indicates that only the LED may be defective.
7.
Check the Driver in full local operation before testing in remote operation,
8.
If a pushbutton does not actuate an attenuator section or change the position of a coaxial switch: ;
a.
Check the output pulses of the A7 Switch Board Assembly either at the A7 outputs or on the
multiplexer inputs of the A4 Remote Local Logic Assembly.
b.
If the pulses are present when the corresponding front panel button is pushed, check the output
of the A4 multiplexers. Verify that the multiplexers are in the local mode of operation.
c.
Verify that the pulse reaches the clock input of A3 Latch Assembly driver storage register flip-
flops. Verify that the Q and NQ outputs change state as the corresponding pushbutton is
exercised.
d.
Measure input and output levels of inverting drivers on the A2 Driver Assembly,
e.
If all logic levels up to the Darlington transistors operate, check for shorted or open Darlington
transistors. For proper operation the voltage across the series base resistor to the Darlington tran¬
sistors should be > 0.5 Vdc when that transistor is on.
To check the Driver in remote operation with no external loads connected, use a logic probe with the
following 9825A controller program:
0:
wrt 728,
"A12345678"
1:
wait 10,
2:
wrt 728,
"B12345678"
3:
wait 10
4:
gto 0
5;
end
a.
Probe A5U4 pin 6 and 9 with the logic probe to verify that the one shot is operating.
b.
Probe A4U2 pin 5 to verify the presence of a pulse that triggers the decoders.
c.
Verify that the A4U9B Listen flip-nop is set High.
d.
Verify that the A4U4A pin 12 Remote Local logic is set High.
e.
Verify that the A5U5 pin 14 Address Comparator is set High.
8-5/8-6
Advertisement
Table of Contents
