HP HP-28S - Test Operations; Repeating Test

Test Operations
There are two system operations for testing the calculator. The first is
a
repeating test of the electronics, which runs without assistance. The
second is a keyboard test, which requires you to press all the keys in a
specified sequence. Both tests
perform a System Halt.
Repeating Test
To perform the repeating test:
1. Start the test.
a. Press and hold 1 ON I.
b. Press~.
c. Release 1 ON I.
2. The display shows horizontal and vertical lines, a blank display,
a
random pattern, and then it briefly displays the result of the
test before starting over .
•
The message OK-2S::: indicates that the calculator passed the
test.
• A message
such as 1 FA I L indicates that the calculator failed
the test. The number indicates the nature of the failure.
If you interrupt the test by pressing a key, the test returns a
failure message
because it didn't expect any keystrokes. Such a
failure message doesn't indicate a
problem with the calculator.
3. Exit the test by performing a System Halt.
a. Press and hold 1 ON I.
b. Press []].
c. Release 1 ON I.
218 25: System Operations