Tandy 600 Service Manual
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The Tandy 600 Portable Computer Service Manual is Tandy's service manual for the Tandy 600, catalogue number 26-3901, "custom manufactured for Radio Shack, a division of Tandy Corporation". The hosted scan has 350 pages, numbered to page 304 with fold-out schematics in section 8. The manual carries no date; the Internet Archive item gives 1986.[1][2]
The preface says the manual is written for service staff in the field and at repair centres, and expects a working knowledge of the 80C88 processor, the 81C55 PIO, the 82C51 USART, the WD2797 floppy controller and the HD61830 LCD controller.[3]
Contents
[edit | edit source]| PDF pages | Section | Contents |
|---|---|---|
| 1-14 | Front matter | Cover, preface (with the board names OPKK, OPLF, OPMP and OPRM), table of contents, lists of illustrations and tables |
| 15-20 | 1. Hardware specifications | Front view, keyboard layout, specifications of the CPU, memory, display, keyboard, floppy drive, modem, RS-232C, clock, printer port, main and backup batteries |
| 21-24 | 2. Connectors, switches and controls | Connector types, the POWER, DIR/ACP, Memory Power and RESET switches, the DISP contrast control |
| 25-46 | 3. Disassembly | Top cover, main board, floppy drive, LCD controller board, keyboard unit, battery and LCD unit; routing of the 34-way drive cable; strip-down of the floppy drive (bezel, PCB, track 00 sensor, carriages, spindle and stepping motors) with the checks to make after each |
| 47-64 | 4. Maintenance and adjustments | Cleaning, modem transmission level, floppy controller VFO, real-time clock frequency, and the floppy drive calibrations with test points and waveforms |
| 65-140 | 5. Operation | Theory of operation: clock, memory map, I/O, interrupts, keyboard, floppy drive and DMA, printer, LCD, serial interface and modem, buzzer, real-time clock, power supply control and the DC/DC converter |
| 141-168 | 6. Troubleshooting | Flowcharts for a machine that will not start, the DC/DC converter, LCD, keyboard, buzzer, real-time clock, memory protection, printer, floppy drive, RS-232C and modem; post-repair check list |
| 169-202 | 7. Exploded views and parts list | Overall, bottom and floppy drive exploded views; parts lists for the OPMP main board, keyboard unit, OPLF board, floppy drive PCB, LCD unit and mechanical parts |
| 203-222 | 8. Circuit diagrams | General block diagram, the main board sheets (including power control, the telephone and modem circuits and the DC/DC converter), and the keyboard, floppy drive, LCD and LCD controller diagrams |
| 223-232 | 9. PCB views | Main board silk-screen, component side, inner layers and circuit side; keyboard and LCD controller boards |
| 233-342 | Appendices A to C | I/O commands, the character code table, and data on the main chips (MSM80C88, MSM82C84, MSM81C55, HD146818, MSM82C51, MSM6946, MSM6234, the RAMs and ROMs, WD2797, µPD8257, HD61830) |
| 343-346 | Appendix D | Fitting the optional RAM card and ROM chip |
Points to note
[edit | edit source]- The parts lists give the type, value, voltage and tolerance of every capacitor on the main board, the floppy drive PCB and the LCD unit; the Tandy 600 Capacitor Replacement Guide tabulates the electrolytic and tantalum parts.[4]
- For two main board capacitors the schematic and the parts list disagree on voltage: C95 is drawn as 16 V and listed as 25 V, and C198 is drawn as 16 V and listed as 10 V.[5][4]
- Section 2 says the RESET switch performs a cold start, while the check list in section 6 describes RESET on its own as a warm start that keeps user files, and RESET pressed with CTRL or PAUSE held as the cold start.[6][7] The owner's manual says RESET leaves RAM intact.[8]
- The floppy drive test in the check list says the test program is saved "on a magnetic tape" and loaded back. The 600 has no cassette port in the section 2 connector list, so the save is to diskette.[7][6]
- The main battery type is printed as "4/4000 RS" without a voltage or capacity.[9]
- The RAM card (OPRM) has no parts list or circuit diagram of its own; section 5 gives a block diagram of the optional RAM (Figure 5-7, PDF page 76).[1]
Pages that cite this document
[edit | edit source]- Tandy 600: specifications, boards, power, disk drive
- Tandy 600 General Maintenance: cleaning, disassembly, batteries, Memory Power switch, RAM and ROM fitting
- Tandy 600 Troubleshooting Guide: Tandy's fault-finding flowcharts and check list
- Tandy 600 Capacitor Replacement Guide: capacitor values from the parts lists and schematics
Download: Tandy 600 Service Manual (26-3901).pdf
References
[edit | edit source]- ↑ 1.0 1.1 Tandy Corporation, Tandy 600 Portable Computer Service Manual, catalogue no. 26-3901, hosted as File:Tandy 600 Service Manual (26-3901).pdf. Cover, preface and contents (PDF pages 1-12); back cover "Printed in Japan" (PDF page 350).
- ↑ "TANDY 600 26-3901 Service Manual", Internet Archive item, metadata and file list (retrieved 2026-10-22). The PDF metadata credits the scan to Brian K. White.
- ↑ Tandy 600 Service Manual, preface (PDF page 5).
- ↑ 4.0 4.1 Tandy 600 Service Manual, section 7.2, parts list (PDF pages 174-176, 195 and 199).
- ↑ Tandy 600 Service Manual, main PCB (OPMP board) circuit diagram, DC/DC converter (PDF page 216).
- ↑ 6.0 6.1 Tandy 600 Service Manual, section 2.2, "Switches" (PDF pages 23-24).
- ↑ 7.0 7.1 Tandy 600 Service Manual, section 6.2, "Check List" (PDF page 168).
- ↑ Tandy Corporation and Microsoft Corporation, Model 600 Owner's Manual, 1985, "Normal Starts, Warm Starts, and Reset", scan at the Internet Archive (retrieved 2026-10-22).
- ↑ Tandy 600 Service Manual, section 1.3, "Hardware Specifications" (PDF page 20).