Radio Shack TRS-80 Model 4 Technical Reference Manual

Radio Shack published two technical reference manuals for the TRS-80 Model 4, and both are hosted here. The 1983 TRS-80 Model 4 Technical Reference Manual (catalogue 26-2110) is the service reference for the original machine, with schematics and parts lists. The later TRS-80 Model 4/4P Technical Reference Manual (catalogue 26-2119, hardware part 1985) adds the theory of operation of the gate array boards and of the TRS-80 Model 4P, but has no parts lists.^[1]^[2]

The 1983 manual (26-2110)

The archive.org scan has 408 pages. Part 1 covers the hardware of the original (non-gate-array) Model 4, catalogue numbers 26-1067, 26-1068 and 26-1069; Part 2 describes the TRSDOS 6 disk operating system. From the table of contents (printed page numbers):^[1]

Section I, Introduction, p. 1: system overview, interconnection diagram, jumper options
Section II, Disassembly/Assembly, p. 7: case, CPU board, floppy controller and RS-232 boards, power supplies, disk drives, monitor and video board
Section III, CPU circuit board, p. 13: theory of operation, I/O bus, schematics and parts lists for the 16 KB and 64 KB boards
Section IV, floppy disk interface, p. 57: controller boards 8858060 (p. 59, with adjustments and jumper options on p. 61) and 8858160 (p. 69)
Section V, mini-disk drive 8790112 (TPI), p. 79: description, theory, interface, maintenance (head cleaning, p. 93) and alignment (pp. 93-96)
Section VI, power supplies, p. 107: Astec 8790021, 38 W (p. 109); Astec 8790043, 65 W, with test set-up, fault finding and performance test (p. 112); Tandy 8790049, 65 W, with specifications, theory, troubleshooting chart and tests (p. 121)
Section VII, video monitors, p. 143: RCA 8492002 with specifications and service adjustments (p. 145), and TCE 8790607 (p. 155)
Section VIII, exploded view and parts list, catalogue 26-1067/8/9, p. 161
Section IX, RS-232C circuit board, p. 167
Part 2, Software: TRSDOS 6 disk organisation (from p. 183), files, system calls and technical information

Download: Radio Shack TRS-80 Model 4 Technical Reference Manual (26-2110, 1983).pdf

The 1985 hardware manual (26-2119)

The hosted scan is the 297-page hardware part only; the software part is not included. From its table of contents:^[2]

Section I, Model 4 theory of operation, p. 1, with the I/O bus and port bits
Section II, Model 4 gate array theory of operation, p. 19: reset circuit, CPU, system timing, address decoding, memory, video, keyboard, ports, cassette, floppy controller and RS-232C
Section III, Model 4P theory of operation, p. 55
Section IV, Model 4P gate array theory of operation, p. 101
Section V, chip specifications, p. 147

Download: Radio Shack TRS-80 Model 4 and 4P Technical Reference Manual, hardware (26-2119, 1985).pdf

What these manuals do not contain

Neither has a parts list or schematic for the gate array Model 4 board. Howard W. Sams' Computerfacts CS13 (1986) covers that board, with schematics and a troubleshooting guide.^[3]
The 1983 manual has no fault-finding section for the CPU board; its troubleshooting covers the power supplies.^[1]
The TRS-80 Model 4D is covered by a separate addendum for its drives and keyboard.^[4]

Pages that cite these documents

TRS-80 Model 4: specifications, boards, power supplies and monitors
TRS-80 Model 4 General Maintenance: disassembly, power supply checks, monitor and floppy controller adjustments, memory jumpers
TRS-80 Model 4 Troubleshooting Guide: power supply fault finding
TRS-80 Model 4 Capacitor Replacement Guide: parts lists for the boards, supplies, monitors and drive

References

↑ ^1.0 ^1.1 ^1.2 Radio Shack, TRS-80 Model 4 Technical Reference Manual, catalogue no. 26-2110, 1983, hosted as File:Radio Shack TRS-80 Model 4 Technical Reference Manual (26-2110, 1983).pdf; title page and table of contents.
↑ ^2.0 ^2.1 Radio Shack, TRS-80 Model 4/4P Technical Reference Manual, catalogue no. 26-2119, hardware part 1985, hosted as File:Radio Shack TRS-80 Model 4 and 4P Technical Reference Manual, hardware (26-2119, 1985).pdf; title page and table of contents.
↑ Howard W. Sams & Co., Computerfacts CS13, Radio Shack TRS-80 Model 4 Gate Array, 1986, archive.org scan.
↑ Tandy Corporation, Addendum to the Model 4 and Model 4 Gate Array Service Manual (Cat. No. 26-1067/8/9) for Model 4D (Cat. No. 26-1070), 1985, archive.org scan.

[trm-1] 1.0 ^1.1 ^1.2 Radio Shack, TRS-80 Model 4 Technical Reference Manual, catalogue no. 26-2110, 1983, hosted as File:Radio Shack TRS-80 Model 4 Technical Reference Manual (26-2110, 1983).pdf; title page and table of contents.

[trm2-2] 2.0 ^2.1 Radio Shack, TRS-80 Model 4/4P Technical Reference Manual, catalogue no. 26-2119, hardware part 1985, hosted as File:Radio Shack TRS-80 Model 4 and 4P Technical Reference Manual, hardware (26-2119, 1985).pdf; title page and table of contents.

[sams-3] Howard W. Sams & Co., Computerfacts CS13, Radio Shack TRS-80 Model 4 Gate Array, 1986, archive.org scan.

[m4d-4] Tandy Corporation, Addendum to the Model 4 and Model 4 Gate Array Service Manual (Cat. No. 26-1067/8/9) for Model 4D (Cat. No. 26-1070), 1985, archive.org scan.

[1]

[2]

[3]

[4]

v t e Tandy / Radio Shack TRS-80, Color Computer, Model 100 and Tandy 1000 Family
TRS-80 Z80 desktops	Model I Model II Model III Model 4 Model 4P Model 4D Model 12 Model 16 Model 16B Model 6000
Color Computer (CoCo)	Color Computer 1 Color Computer 2 Color Computer 3 MC-10 Micro Color Computer
TRS-80 / Tandy portables (Model 100 family)	Model 100 Tandy 102 Tandy 200 Tandy 600 Tandy 1100 FD Tandy 1110 HD Tandy 1400 LT
Tandy 1000 family (PC-compatible)	Tandy 1000 Tandy 1000A Tandy 1000 HD Tandy 1000 EX Tandy 1000 SX Tandy 1000 HX Tandy 1000 TX Tandy 1000 SL Tandy 1000 SL/2 Tandy 1000 TL Tandy 1000 TL/2 Tandy 1000 TL/3 Tandy 1000 RL Tandy 1000 RL-HD Tandy 1000 RSX Tandy 1000 RLX
Tandy 2000 / 3000 / 4000 / 5000 (PC-compatible)	Tandy 2000 Tandy 3000 Tandy 4000 Tandy 5000 MC
Pocket Computers	PC-1 PC-2 PC-3 PC-4 PC-5 PC-6 PC-7 PC-8