TRS-80 PC-3 General Maintenance

Changing the cells, steps 1 to 6, from the PC-3 owner's manual (pp. 20-21).

Care of the TRS-80 PC-3 (catalogue numbers 26-3590 and 26-3589) and its 26-3591 printer/cassette interface, from Radio Shack's owner's manual. No Radio Shack service manual for the PC-3 has been found. The computer is a Sharp PC-1250 or PC-1251, and Sharp's service manual for those, summarised on Sharp PC-1251 General Maintenance, covers work inside the case. Faults are covered on TRS-80 PC-3 Troubleshooting Guide.

Cells

The PC-3 runs from two CR-2032 lithium cells, which Radio Shack rated at about 300 hours. The sign that they need changing is a display that stays dim and hard to read from the front even with the contrast control turned fully anticlockwise. The manual says to save programs and data to tape first if you have the printer/cassette interface, and to clear the computer with RESET once the new cells are in.

Radio Shack's rules: replace both cells together, do not mix a new cell with a used one, and use only CR-2032 lithium cells.

1. Switch the computer off with the power slide switch.
2. Remove the screws from the back cover with a small screwdriver.
3. Slide the battery cover off in the direction of the arrow.
4. Fit the two new cells, observing polarity.
5. Slide the battery cover back on.
6. Hook the claws of the back cover into the slots in the computer.
7. Press the back cover in slightly while refitting the screws.
8. Switch on and press the RESET button. The prompt should appear.

If the display stays blank or shows anything other than the prompt, take the cells out, refit them and check again. In step 5 the manual refers to "the arrow shown in figure 2"; the arrow meant is the one in figure 10.

Remove dead cells promptly, and take the cells out if the computer will not be used for a long time, because a leaking cell can damage it. If a cell has leaked, see Battery Explosion, Capacitor or Corrosion Damage.

Contrast

The contrast control is on the right-hand side of the computer. Turning it in the direction of the arrow brightens the display and the other way dims it; set it so the display is easy to read.

Handling and cleaning

Radio Shack's maintenance advice:

• Handle the computer carefully: the display is glass.
• Keep it away from extreme changes of temperature, moisture and dust. A car left in the sun in warm weather can get hot enough to damage it.
• Clean it only with a soft, dry cloth; no solvents, water or wet cloths.
• Strong static or electrical noise can make it "hang up" with every key dead; the cure is on TRS-80 PC-3 Troubleshooting Guide.

The 26-3591 printer/cassette interface

The interface has a 24-column thermal printer, a cassette interface for an ordinary recorder, and built-in rechargeable NiCd cells.

• Charge it when the low-battery indicator comes on; the interface stops working at that point. Switch off the computer and the interface, connect the AC adapter to the interface first and then plug it into the wall. A full charge takes about 15 hours.
• Use only the adapter supplied. Radio Shack warns that any other may damage the interface.
• A new interface was likely to need charging before first use after time in storage.
• Switch both units off before connecting or disconnecting the computer, or the computer may hang. Move the protective pin cover from the computer's left side to its place on the bottom of the interface.
• Use the printer on a level surface, keep it away from extremes of temperature, moisture, dust and loud noise, clean it with a soft dry cloth, and keep foreign objects out of it.
• When docked, the interface supplies the computer if the computer's own cells run low.

Capacitors

See TRS-80 PC-3 Capacitor Replacement Guide.

Related pages

• TRS-80 PC-3
• TRS-80 PC-3 Troubleshooting Guide
• TRS-80 PC-3 Capacitor Replacement Guide
• TRS-80 PC-3 Documentation
• Sharp PC-1251 General Maintenance