TRS-80 PC-7 Capacitor Replacement Guide
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No parts list, schematic or board photograph of the TRS-80 PC-7 or of the Casio FX-5200P it is based on is available from the Floodgap archive, the Internet Archive or the Pocket Museum, so no capacitor values for the PC-7 are published, and it is not confirmed that the board has any electrolytic capacitor at all.[1] The PC-7's two documented relatives each have a few electrolytics in their supply, listed below as a guide to what to look for. Neither board is the PC-7's.
What the relatives have
[edit | edit source]| Model | Electrolytics | Where | Source |
|---|---|---|---|
| TRS-80 PC-4 | 10 µF 16 V; 4.7 µF 35 V | Supply reservoir after the diode from the cells; near the RAM | PC-4 service manual parts list and schematic[2] |
| TRS-80 PC-6 | C11, C12 22 µF 10 V; C13 100 µF 10 V | Option connector supply; memory backup circuit; main supply after the diode from the cells | PC-6 service manual parts list and schematic[3] |
Kaiser describes the PC-7 as a PC-5 with one processor, no backup cell and no expansion port.[1] If that holds for the board, the PC-6's backup-circuit and option-connector capacitors have no counterpart on a PC-7, and a supply reservoir capacitor across the cells is the most likely electrolytic to find.
Recording your own board
[edit | edit source]- Write down any programs you want to keep; the PC-7 cannot save them and loses its memory when the cells are removed.[1]
- Remove the cells and open the case on an earthed mat, keeping both halves supported so that the ribbon cable across the join is not pulled; see TRS-80 PC-7 General Maintenance.
- Photograph both sides of the board.
- Look for aluminium electrolytics: small cans with a printed value in µF and a stripe on the negative side. Note each one's reference, value, voltage and orientation.
- On the PC-4 and PC-6 schematics the cells' positive side is the line marked GND, so expect a supply electrolytic to have its positive lead on GND. Fit any replacement exactly as the original faced.[2][3]
See also Capacitor Failure Symptoms.
Related pages
[edit | edit source]- TRS-80 PC-7
- TRS-80 PC-7 General Maintenance
- TRS-80 PC-7 Troubleshooting Guide
- TRS-80 PC-4 Capacitor Replacement Guide and TRS-80 PC-6 Capacitor Replacement Guide
References
[edit | edit source]- ↑ 1.0 1.1 1.2 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. The PC-7 as a cut-down PC-5 with one CPU, the PC-4's LCD and no battery backup; the Floodgap archive's lack of PC-7 documentation.
- ↑ 2.0 2.1 Radio Shack, Service Manual: TRS-80 PC-4 Pocket Computer and Cassette Interface. Hosted as File:Radio Shack TRS-80 PC-4 Pocket Computer and Cassette Interface Service Manual (26-3650).pdf. Schematic p. 22; parts list pp. 26–27.
- ↑ 3.0 3.1 Tandy, Service Manual: Pocket Scientific Computer PC-6. Hosted as File:Tandy PC-6 Pocket Scientific Computer Service Manual (26-3672).pdf. Parts list p. 20; schematic p. 24.