TRS-80 PC-4 Documentation

Three Radio Shack manuals for the TRS-80 PC-4 pocket computer and its options are hosted here. All three are scans from the Floodgap Retrobits Tandy Pocket Computer archive.

Service manual (26-3650, 26-3651, 26-3653)

The Service Manual: TRS-80 PC-4 Pocket Computer and Cassette Interface is Radio Shack's service manual for the PC-4 computer (26-3650), the cassette interface (26-3651) and the 1K RAM module (26-3653). The scan has 34 pages: the cover, printed pages 1 to 32, and the contents page, which is bound at the back. The PDF's embedded title is "Tandy PC-4 Computer and Cassette Service Manual".

Contents

From the contents page, with printed page numbers:

• I. Pocket computer and memory module: specifications (p. 1), block diagram (p. 3), CPU HD61913 features, block diagram and signal descriptions (pp. 4–5), RAM (p. 6), servicing: disassembly (p. 7), troubleshooting of the display, key entry, RAM1, RAM2 and CPU against RAM1 (pp. 8–10), test program (p. 11), program command list (p. 13), error message list (p. 15)
• II. Cassette interface: specifications and block diagram (p. 16), the HD43110 interface chip (p. 17), clock, remote control and shaping circuits (p. 18), disassembly (p. 20) and troubleshooting (p. 21)
• III. Circuit diagrams of the 26-3650 (p. 22) and 26-3651 (p. 23)
• IV. Printed circuit boards of the 26-3650, 26-3651 and 26-3653 (p. 24), and the exploded view of the 26-3650 (p. 25)
• VI. Parts lists of the 26-3650 (pp. 26–28) and 26-3651 (pp. 29–32)

What this manual does not contain

• No reference designators: the parts lists give descriptions and manufacturer part numbers, and the schematics give values without C or R numbers.
• No parts list for the 26-3653 RAM module, only its board drawing.
• Nothing on the 1985 26-3650B; the manual covers the original 26-3650.
• A 1 µ 50 V capacitor drawn on the schematic has no entry in the parts list.

Pages that cite this document

• TRS-80 PC-4 – specifications, chips and options
• TRS-80 PC-4 General Maintenance – disassembly and the mechanical parts list
• TRS-80 PC-4 Troubleshooting Guide – fault tables, test programs, error codes and pin voltages
• TRS-80 PC-4 Capacitor Replacement Guide – the electrolytics and the supply circuit

Download: Radio Shack TRS-80 PC-4 Pocket Computer and Cassette Interface Service Manual (26-3650).pdf

Owner's manual (26-3650A)

The TRS-80 PC-4 Owner's Manual, catalogue number 26-3650A, is the 72-page user manual. It covers use precautions (p. 3), power supply and battery replacement (p. 4), the names of the parts and the keyboard (pp. 5–9), contrast adjustment and the RAM expansion pack (pp. 11–12), calculation and BASIC programming (pp. 14–60), the error message list (p. 61), the program command list (p. 62), function digit capacity (p. 64) and the specifications (pp. 65–66). It has no service information beyond the battery and RAM pack procedures.

Cited by TRS-80 PC-4, TRS-80 PC-4 General Maintenance and TRS-80 PC-4 Troubleshooting Guide.

Download: Radio Shack TRS-80 PC-4 Owner's Manual (26-3650A).pdf

Cassette interface owner's manual (26-3651)

The TRS-80 PC-4 Cassette Interface Owner's Manual, catalogue number 26-3651, is a 24-page manual for the interface that connects the PC-4 to an ordinary cassette recorder. Its introduction (p. 4) warns that a wrong connection will not damage the computer or the recorder but can stop programs saving or loading and can erase data.

Cited by TRS-80 PC-4 Troubleshooting Guide.

Download: Radio Shack TRS-80 PC-4 Cassette Interface Owner's Manual (26-3651).pdf