TRS-80 Color Computer
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| TRS-80 Color Computer, with the cartridge slot on the right-hand side (photo: Bilby, CC BY 3.0) | |
| Specifications | |
|---|---|
| Manufacturer | Tandy Corporation (sold through Radio Shack) |
| Type | Home computer |
| Released | 31 July 1980 |
| Intro price | US$399.00 (26-3001, 4K); US$599.00 (26-3002, 16K with Extended BASIC) |
| CPU | Motorola MC6809E, 0.89 MHz |
| Memory | 4K or 16K dynamic RAM at launch; later 32K and 64K |
| Storage | Cassette, about 1,500 baud; ROM cartridges ("Program Paks") |
| Display | MC6847 video display generator, RF output to a television; 32 x 16 text, graphics to 256 x 192 |
| Sound | 6-bit D/A converter |
| ROM | 8K Color BASIC; Extended Color BASIC on the 26-3002 |
| Power | Mains transformer inside the case; +5 V, +12 V, −12 V and −5 V regulated on the main board |
| OS / Firmware | — |
| Successor | TRS-80 Color Computer 2 |
| Model no. | 26-3001, 26-3002, 26-3003; revised 26-3002A, 26-3003A, 26-3004A |
The TRS-80 Color Computer is a home computer that Radio Shack introduced on 31 July 1980, built round the Motorola 6809E and connected to a colour television. It was sold at first as the 4K Color Computer (catalogue number 26-3001, $399.00) and the 16K Color Computer with Extended BASIC (26-3002, $599.00); a 32K model, 26-3003, followed in 1982. It is now usually called the Color Computer 1 to tell it from the TRS-80 Color Computer 2 of 1983 and the TRS-80 Color Computer 3.[1]
Specifications
[edit | edit source]| Item | Detail |
|---|---|
| CPU | MC6809E (U1); the E and Q clocks, 0.89 MHz, come from the SAM |
| Memory control | MC6883 synchronous address multiplexer (SAM, U10): RAM refresh and address multiplexing, system timing and device selection |
| RAM | Eight dynamic RAMs, U20 to U27, 4K or 16K |
| ROM | MCM68A364 (U3) |
| Video | MC6847 video display generator (U7), MC1372 video mixer, RF modulator (U5) |
| I/O | Two MC6821 PIAs (U4 and U8): keyboard, joysticks, 6-bit D/A converter for sound and cassette, RS-232 and VDG mode control |
| Connectors | 40-pin cartridge connector (P1); RS-232, 4-pin DIN (P2); two joystick sockets, 6-pin DIN (P3, P4) |
| Power | +5 V at up to 1.35 A, +12 V at 400 mA, −12 V at 100 mA, −5 V at 100 µA |
Sources: the service manual's system description, theory of operation, troubleshooting chip list and parts list.[2]
Hardware
[edit | edit source]Main board revisions
[edit | edit source]Tandy's technical bulletins describe two generations of main board. The "old style" boards, revisions B to E, include the revision D board (AXX-0338) and revision E board (AX-9003) used in the 26-3001, 26-3002, 26-3003 and 26-3004. The revised Color Computers, catalogue numbers with an A suffix (26-3002A, 26-3003A, 26-3004A), use the AX-9328 board. The changes between the two include a new keyboard, an MC6822 keyboard PIA in place of the MC6821, a different power supply board on the same transformer, a different MC1372P video mixer that looks identical to the old one, and a different cassette relay.[3] The revision B board cannot take the 64K upgrade; revision D and E boards can, with the cuts and jumpers in bulletin CC:15.[3]
Power supply
[edit | edit source]The mains transformer sits on its own board inside the case, with a 0.7 A fuse and three 0.01 µF 1 kV capacitors (C20 to C22) on the primary. One centre-tapped secondary, 16.3 V AC at 1 A, feeds the +5 V supply alone; the other, 33.5 V AC at 0.35 A, feeds bridge CR11 for the +12 V, −12 V and −5 V supplies. The +12 V comes from a 78M12 regulator (U17); the +5 V supply is a 723C regulator (U13) driving pass transistor Q2 through Q3, with C10 filtering its input and C16 its output, protected by a 6.2 V zener, CR17, that shorts the rail if it goes too high. The +5 V regulator is powered from the +12 V supply, so a +12 V failure also takes out +5 V.[2][4] Mains voltage is present on the transformer board whenever the computer is plugged in.
Known faults
[edit | edit source]- Tandy found some revision D and E boards with C18, the 1 µF tantalum capacitor on the −5 V regulator, fitted backwards. It fails when it overheats and burns, and the −5 V supply fails with it.[3]
- The revised 26-3002A, 26-3003A and 26-3004A can lock up after 30 minutes to two hours, after random characters fill the second and ninth columns of the screen. Tandy's fix was a satellite board kit, AX-7089.[3]
- After a 32K upgrade, the diagnostic cartridge may report "64K MEMORY U21 BAD" or "U26 BAD" because of a jumper wired to the wrong pin in the original upgrade instructions.[3]
See the TRS-80 Color Computer Troubleshooting Guide for the service manual's fault-finding procedure.
Documentation
[edit | edit source]- Radio Shack TRS-80 Color Computer Service Manual: Radio Shack's service manual for the 26-3001 and 26-3002, with theory of operation, troubleshooting, parts list, board drawings and schematics.
- File:Tandy Color Computer Technical Bulletins CC-1 to CC-32.pdf: Tandy's technical bulletins for the whole Color Computer range, 1980 to 1988.
Related pages
[edit | edit source]- TRS-80 Color Computer General Maintenance
- TRS-80 Color Computer Troubleshooting Guide
- TRS-80 Color Computer Capacitor Replacement Guide
- TRS-80 Color Computer 2
- TRS-80 Color Computer 3
- Tandy TRS 80
References
[edit | edit source]- ↑ Matthew Reed, "The TRS-80 Color Computer", TRS-80.org (retrieved 2026-10-21). Introduction on 31 July 1980; the 26-3001 at $399.00 and 26-3002 at $599.00; the 32K 26-3003 in the 1982 catalogue; the 6809E at 0.895 MHz, 53-key keyboard, 32 by 16 text and graphics to 256 by 192; the Color Computer 2 announced on 9 September 1983; the last Color Computer 1, a 64K model in a white case with a typewriter-style keyboard, in the 1984 catalogue.
- ↑ 2.0 2.1 Radio Shack, Service Manual: Color Computer, catalogue numbers 26-3001/3002, hosted as File:Radio Shack TRS-80 Color Computer Service Manual (26-3001, 26-3002).pdf, described at Radio Shack TRS-80 Color Computer Service Manual. System description and block diagram (pp. 2 and 3); the 6809E and its 0.89 MHz clocks from the SAM (p. 20); the joysticks on P3 and P4; RS-232 interface and system power supply (pp. 36 and 37); fault isolation and the chip list (p. 47); printed circuit board parts list, including connectors P1 to P7 (pp. 53 and 54).
- ↑ 3.0 3.1 3.2 3.3 3.4 Tandy Corporation, Color Computer Technical Bulletins CC:1 to CC:32, hosted as File:Tandy Color Computer Technical Bulletins CC-1 to CC-32.pdf. CC:3 (C18 fitted backwards on revision D and E boards); CC:15 (64K upgrade of revision B to E boards); CC:16 (U21 or U26 BAD errors after a 32K upgrade); CC:17 (parts changed between the old-style AXX-0338 and AXX-9003 boards and the new-style AX-9328 board); CC:20 (lock-up after warm-up on the revised 26-3002A, 3003A and 3004A).
- ↑ Service Manual: Color Computer (26-3001/3002), Section IV, Troubleshooting, pp. 47 to 49: fault isolation, supply test points TP9 to TP12 and TP3 (ground), RAM supply pins, the chip substitution list, diagnostic notes for video, joystick, cassette, keyboard and RS-232 faults, and the power supply section with Figure 1, "Power Supply Voltage Levels".