RAC Plus User’s Manual
3-6
Step 2
The Tap Test will determine if the dis-
tance pulses being sent from the MDS
are getting to, and being processed by,
the RAC. The Tap Test is performed
using the rotary switch shown in gure
3.6. First make sure you note the cur-
rent position of the rotary switch (1, 2,
4, 8,16, 32 or 64), as you will have to
return the slot back to this same position after the test is completed.
Next, turn on the RAC. Press the CH key just like you were beginning to
measure. Using a small screwdriver, rotate the switch between the Tap and
Test positions four or ve times. (Note that when the switch is turned clock-
wise until it stops, it is at the Test position.) The RAC should register. The
count shown does not matter, just as long as the RAC did register a count.
If it did count, the cable from the MDS to the RAC and the instrument itself
are OK. If the RAC did not count, the problem is most likely a bad cable to
the RAC or the RAC itself is bad. If available, try another RAC and repeat
the Tap Test. If the second RAC doesn’t count, the problem has to be the
cable between the MDS and the RAC.
Once the test is complete, return the Rotary Switch to the previous posi-
tion.
If the previous steps do not correct the problem, contact us using the infor-
mation on page iii.
Fig. 3.6 – Tap Test
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