HP HP-28S - Calculator Maintenance; Environmental Limits; Determining if the Calculator Requires Service

Calculator Maintenance
To clean the display, use a cloth slightly moistened with water. Avoid
getting the calculator wet.
Do
not lubricate the hinge.
Environmental Limits
In order to maintain product reliability, you should observe the fol-
lowing temperature and humidity limits of the HP-28S:
•
Operating temperature: 0° to 45°C (32° to 113°F).
• Storage
temperature: - 20° to 65°C (- 4° to 149°F).
•
Operating and storage humidity: 90% relative humidity at 40°C
(104°F) maximum.
Determining If the Calculator Requires
Service
Use these guidelines to determine whether the calculator is function-
ing properly. If the calculator does require service, see "Limited One-
Year Warranty" on page 291 and "If the Calculator Requires Service"
on page 293.
If nothing appears in the display when you press I ON I:
1. Check the display contrast.
a. Press and hold I ON I.
b. Press GJ several times.
c. Release I ON I.
d. If the display remains blank, press ION 1 and repeat steps a,
b,
and c.
A: Assistance, Batteries, and Service 289