Jump to content

TRS-80 PC-5 Capacitor Replacement Guide

From RetroTechCollection
Tandy PC-6 power supply and memory backup schematic (service manual 26-3672)
Supply section of the PC-6 schematic, the nearest published circuit to the PC-5. It shows electrolytics C11, C12 and C13. No PC-5 schematic is available

Neither the Floodgap archive nor the Internet Archive holds a parts list or schematic for the TRS-80 PC-5, so no capacitor values for it are published. The nearest documented board is the TRS-80 PC-6, whose service manual Cameron Kaiser says applies generally to the PC-5.[1] The two models differ in their processors and memory, so the PC-6 values below are a guide to what to expect on a PC-5, not a PC-5 parts list.

What the PC-6 has

[edit | edit source]

The PC-6 has three electrolytic capacitors, all in the supply.[2]

PC-6 electrolytics (PC-6 service manual p. 20) – not confirmed for the PC-5
PC-6 ref. Value Rating Position on the PC-6 schematic
C11 22 µF 10 V At the 12-pin option connector, between GND and VDD1
C12 22 µF 10 V In the memory backup circuit beside the CR1220
C13 100 µF 10 V Across the main supply from the two CR2032 cells, after diode D3

The PC-5 has the same cell arrangement, two CR2032 cells and a CR1220 backup, and takes the same peripherals through the same 26-3671 link cable, so capacitors in the same three places are likely. Confirm them on your own board.[1][3]

Recording your own board

[edit | edit source]
  1. Save any programs to tape, then open the case. The nearest published procedure is the PC-6's; see TRS-80 PC-6 General Maintenance#Opening the case.
  2. Photograph both boards before touching anything.
  3. Find every aluminium electrolytic: a can with a printed value, usually in µF, and a stripe on the negative side.
  4. Write down the reference printed beside each on the board, the capacitance, the voltage and the orientation.
  5. Compare them with the PC-6 table above. Where the reference and value match, the PC-6 notes apply; where they differ, go by your board.
  6. Replace with the same capacitance and the same or a higher voltage, in the same orientation, one part at a time.

Tandy's PC-6 fault table names no capacitor among the causes of faults; cells, battery springs, heat seals, the LCD and key contacts come first.[2] See the TRS-80 PC-5 Troubleshooting Guide before recapping a PC-5 that does not work.

See also Capacitor Failure Symptoms and TRS-80 PC-6 Capacitor Replacement Guide.

[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.0 1.1 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-6 service manual generally applying to the PC-5; the PC-5's HD61747B10/B11 processors and 4 KB memory against the PC-6's HD61747B20/B25 and 8 KB.
  2. ↑ 2.0 2.1 Tandy, Service Manual: Pocket Scientific Computer PC-6, catalogue number 26-3672. Hosted as File:Tandy PC-6 Pocket Scientific Computer Service Manual (26-3672).pdf. PCB assembly view p. 19; electrical parts list p. 20; disassembly p. 23; main block schematic p. 24.
  3. ↑ Pocket Museum, "The Tandy PC-5 computer (26-3670)". Retrieved 2026-10-21. Power: two CR2032 and one CR1220 lithium batteries.


Retrieved from "https://retrotechwiki.com/index.php?title=TRS-80_PC-5_Capacitor_Replacement_Guide&oldid=28675"