HP 5334B Service Manual page 164

8-317. The COMMONISEPARATE A function can be checked:
a. Remove any input signal from the Counter and set the input impedance to 1 MR.
b. Measure the resistance across the contacts of relays K7 and K8. In the Separate mode, K7 should be
open and K8 should be closed. The resistance between pins 1 and 4 of K7 should be approximately
2 MCl. In the Common A mode, K7 should be closed, and K8 should be open. In this case, the resis-
tance across K8, pins 1 and 4, should be greater than 10 MCl. When closed, both relays should
measure less than l R between pins 1 and 4.
8-318. If the SeparateICommon A function does not work:
Check the relay control voltage at pin 3 of relay K7 (or anode of CR30) and relay K8 (or anode of CR31). The
voltage is a 'ITL HIGH level when the relay is open and a
'ITL LOW level when closed.
8-319. The Channel
A
100 kHz FILTER function can be checked:
a. Apply a 100 kHz, 1 volt peak-to-peak sine wave signal to the Channel A Input with the input im-
pedance set to 50R. Note
-
set HP3325A AMPTD to . ! W to generate a 1V p-p signal.
b. Set 5334B INPUT A to DC coupling.
c. With the Filter A function switched OFF, the amplitude at pin
1
of Filter Relay K2 (or R94 and C74
junction) should be approximately 350 millivolts p-p. When Filter A is turned ON, the amplitude
drops to approximately 130 millivolts peak-to-peak.
8-320. If the Filter Relay does not work:
a. Check the relay control voltage at pin 3 of relay K2 (or anode of CR21). The voltage is a TTL LOW
level when the Filter
A
function is OFF and a 'ITL HIGH level when the filter is selected.
b. Set 100 kHz Filter A to OFF.
8-321. In the HIGH-LOW FREQUENCY AMPLIFIER STAGE, the most likely failure will be one of the four
active components in the circuit: Q8, Q10, Q6, and U30.
A
problem in one frequency path may cause faulty sig-
nal voltages in the other. Since the two paths may cause faulty signal voltages in the other, this stage must be
checked by tracing both high and low frequency signals through the circuit followed by various dc checks. Note
that a 10:1,10 MR oscilloscope probe must be used at the gate of Q8 and at the inputs of operational amplifier
U30 to prevent loading down the signal.
8-322. To check the HIGH FREQUENCY path set the equipment as follows:
5334B Signal Source
FREQ A
...........................................
ON
1
MHz,
1
Volt peak-to-peak sine wave
(set 3325A AMPTD to .5V to generate 1V p-p signal)
0 volt, dc offset
50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
AUTO TRIG
...................................
OFF
a.
Apply the 1 MHz signal to the Channel A Input.
b. Adjust the TRIGGER LEVELISENS control for a 0 volt dc level at the emitter of Q10.
c. Measure approximately 350 millivolts p-p at the emitter of Q10.
HP 5334B
-
Service Manual
8-44