HP 35s Scientific Calculator - Manual (Page 292)

A-6 Support, Batteries, and Service
 →  →  → 9 → Ч → Ц → Х →  →  →
 → 6 → Ш →  →  →  →  →  →  →
 →  →  → 4 →  →  →  →  →  →  →  →
 →  →  →  →  →  →  →  →  →  →  →  →
 → 
If you press the keys in the proper order and they are functioning properly,
the calculator displays  followed by two–digit numbers. (The
calculator is counting the keys using hexadecimal base.)
If you press a key out of order, or if a key isn't functioning properly, the
next keystroke displays a fail message (see step 4).
4. The self–test produces one of these two results:
The calculator displays  if it passed the self–test. Go to step 5.
The calculator displays  followed by a one–digit number, if it
failed the self–test. If you received the message because you pressed a key
out of order, reset the calculator (hold down
 , press  ) and do the
self test again. If you pressed the keys in order, but got this message,
repeat the self–test to verify the results. If the calculator fails again, it
requires service (see page A–8). Include a copy of the fail message with
the calculator when you ship it for service.
5. To exit the self–test, reset the calculator (hold down  and press  ).
Pressing  and
9
starts a continuous self–test that is used at the factory.
You can halt this factory test by pressing any key.