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4-6 Status Display Board Diagnosis
Error Rate Testing With the Status Display Board
The Status Display Board can be used for error rate testing of up to two drives at a time. It
counts the number of passes of the selected self-test, and counts errors separately for each
drive. This is the procedure:
1. Attach a jumper between the loop pins.
2. Put a disc with no defective tracks in each drive, and close the door.
3. Turn the power on.
4. Press the write enable switch and hold it in while pressing the self-test switch. Hold the
self-test switch in with an insulated clip. The write/read test will now run continu-
ously.
5. The HP bit error rate standard is no more than one error in 10
9
bits. 7862 passes are
the equivalent of 10
9
bits. A drive would pass if it has no more than five errors in
39,308 passes. A problem arises in that the pass counter only counts to 9999 and then
re-sets. This problem may be circumvented in one of two ways. Put the system into
operation and allow it to run for an hour or two. If errors have accumulated, the drive
is defective. To prove that a drive is good, determine the length of time the system
takes to make a countable number of passes, say 3,000 or 10,000 and then calculate
how long 39,308 would take. Allow the system to run for that length of time, and stop
when the counter reads 9308. If no more than five errors have accumulated on a
drive, it is a good drive.
6. Note that the self-test routine cannot determine whether a track is good or bad, but
attempts to write on every track. If errors appear to occur at the same point on the
disc, there is probably a defective track at that point.
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