TRS-80 PC-5 General Maintenance
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The TRS-80 PC-5 runs from two CR2032 lithium cells and keeps its memory on a CR1220. Its maintenance is the cells, the clamshell's hinges and front latch, and the membrane keyboard. No Tandy manual for the PC-5 is available; the Floodgap archive points owners to the PC-6 service manual, which Cameron Kaiser says applies generally to the PC-5.[1] Steps taken from the PC-6 manual are marked as such; the full PC-6 procedures are in TRS-80 PC-6 General Maintenance.
Cells
[edit | edit source]The Pocket Museum lists two CR2032 cells and one CR1220 for the PC-5, the same set as the PC-6.[2] The CR1220 holds the RAM while the main cells are out, so change the main pair and the backup cell at different times, never together, and save programs to tape first.[1]
The PC-6 service manual's parts list gives a separate holder for each cell type, with a 1.7 mm machine screw for the CR2032 pair and a 2 mm tapping screw for the CR1220, and its fault table gives poor battery contact as a cause of a blank display: clean the cell and the spring, and lift the spring.[3] Check your own PC-5 against that before ordering parts. If a cell has leaked, see Battery Explosion, Capacitor or Corrosion Damage.
Hinges and latch
[edit | edit source]Kaiser reports that most PC-5 and PC-6 units on the second-hand market have broken hinges or latches, and that there is no easy repair. To protect the hinges, press on the hinge covers with a finger as you open the lid, or tape over them.[1]
A 3D-printed replacement latch for the PC-5, PC-6, FX-780P and FX-790P was published on Thingiverse in 2022 under a CC BY 4.0 licence. Trim the broken latch so that it fits inside the pocket in the printed part, check the fit, and glue it in place.[4]
Keyboard
[edit | edit source]The letters are on a membrane panel in the lid, and the numbers and functions on moulded keys in the base. Kaiser describes the membrane as mushy and says it flexes in use.[1] For a dead key, the PC-6 manual's remedy is to clean the contact pads on the board and the key contact rubber.[3]
Things that are not faults
[edit | edit source]- There is no RESET button on the front of a PC-5. The PC-6 has one; the PC-5 does not.[1]
- The memory expansion slot inside is covered by a plastic sticker. Kaiser doubts that the PC-5 would use a RAM pack even if one were connected.[1]
Opening the case
[edit | edit source]Without a PC-5 service manual, the nearest procedure is the PC-6 manual's (three screws from the lower case, then nine plus two screws from the board holders) in TRS-80 PC-6 General Maintenance#Opening the case. The two models share a case, but check each screw position on your own unit.[3][1] On the PC-6 the two circuit boards are joined by a heat-sealed flexible connector, so lift the boards without folding or pulling on anything that joins them.
Related pages
[edit | edit source]- TRS-80 PC-5
- TRS-80 PC-5 Troubleshooting Guide
- TRS-80 PC-5 Capacitor Replacement Guide
- TRS-80 PC-6 General Maintenance
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Cameron Kaiser, "Tandy Radio Shack Pocket Computer PC-4 and Tandy Pocket Scientific Computer PC-5, PC-6, PC-7", Floodgap Retrobits, Tandy! Pocket! Mania!. Retrieved 2026-10-21. PC-5 and PC-6 section: the backup battery; the membrane keyboard; hinges splitting and latches cracking, and pressing on the hinge covers or taping them; the PC-5's covered memory slot; the PC-6 service manual generally applying to the PC-5.
- ↑ Pocket Museum, "The Tandy PC-5 computer (26-3670)". Retrieved 2026-10-21. Power: two CR2032 and one CR1220 lithium batteries.
- ↑ 3.0 3.1 3.2 Tandy, Service Manual: Pocket Scientific Computer PC-6, catalogue number 26-3672 (no PC-5 manual is available). Hosted as File:Tandy PC-6 Pocket Scientific Computer Service Manual (26-3672).pdf. Troubleshooting guide p. 10; mechanical parts list pp. 21–22; exploded view and disassembly p. 23.
- ↑ Thingiverse thing 5409498, "Tandy PC-5, PC-6 or Casio FX-780P, FX-790P latch", CC BY 4.0. Archived copy at the Internet Archive, thingiverse-5409498. Retrieved 2026-10-21. Replacement latch for the Tandy PC-5/PC-6 (Casio FX-780P/FX-790P); trim the broken latch, test the fit and glue it in place.