TRS-80 Model 16 General Maintenance
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Tandy's service manual for the TRS-80 Model 16 covers only the 68000 side of the machine: the MC68000 CPU board and the 128K/256K memory board. For the Z80 side it refers to the Model II technical reference and service manuals.[1] It has no disassembly or adjustment procedures. The practical points below come from that manual and from community repair notes; the TRS-80 Model II General Maintenance guide covers the Model II, whose Z80 design the Model 16 shares, though its boards and power supply carry different part numbers.[2]
 | The power supply runs from the mains, and the CRT can hold a charge after switch-off. The trs-80.com notes report that the bleeder resistor in the anode cap can fail open, as it did in the writer's own Model 16, so do not rely on it: discharge the tube as described in the CRT Discharge Procedure. |
Assemblies
[edit | edit source]The service manual's mechanical parts list names these field-replaceable assemblies:[2]
| Assembly | Tandy part no. |
|---|---|
| Power supply (13 A) | 8790040 |
| 12-inch CRT display kit | 8790606 |
| CRT display (reworked) | 8898021 |
| Disk drive | 8790119 |
| Z80 CPU board (8-bit) | 8898020 |
| MC68000 CPU board (16-bit) | 8898000 |
| Floppy disk controller board | 8898019 |
| 64K memory board | 8893498 |
| 128K memory board | 8898001 |
| Video board | 8898018 |
| Card cage assembly | 8898100 |
Power supply
[edit | edit source]The supply must provide +5 V at 13.36 A, +12 V at 2.5 A, −12 V at 200 mA and +24 V at 1.7 A.[4] The Model 16 manual gives no test procedure for it. The trs-80.com notes point out that switching supplies of this period generally need a load to regulate properly and can be damaged by running unloaded, and that Astec supplies were tested fully loaded. The same notes point to a load box described in the Model II Technical Reference Manual.[3] Test the supply with its boards connected or on a load.
Boards
[edit | edit source]- Handle the boards with static precautions. The trs-80.com notes stress that static damage is cumulative: a part may survive one or two discharges and fail on the third.[3]
- The 68000 CPU board's interrupt jumpers are E19 to E16 and E3 to E10; Tandy's troubleshooting chart lists them as a check when the interrupt test hangs.[5]
- The 128K/256K memory board can be jumpered to sit on any 256 KB boundary of the 68000's 7 MB address space, and has optional parity. The 64 KB Z80 memory board has a jumper to select one of 15 memory pages.[4] Check these jumpers against the configuration before suspecting a board.
Disk drives
[edit | edit source]The Model 16 holds one or two Tandon Thinline 8-inch drives (Tandy 8790119), which take single- or double-sided disks at single or double density.[4][2][6] Write precompensation on the floppy controller board is adjustable from 0 to 350 ns.[4] Tandy's later manual for the Model 16B built-in hard disk system asks for the floppy drives to be checked by a Radio Shack technician every six months or less, and gives a preventive maintenance interval of 8,000 power-on hours in typical use (about 3,000 hours a year) or 5,000 in heavy use.[7] See also Floppy Drive Repair.
Diagnostics
[edit | edit source]Tandy's procedure starts with the Model II diagnostics, which test the Z80 side, and then uses the MOD16 memory, interrupt, offset/limit and modified address tests for the 68000 boards. See the TRS-80 Model 16 Troubleshooting Guide.[5]
Capacitors
[edit | edit source]The 68000 CPU board's electrolytics are listed in the TRS-80 Model 16 Capacitor Replacement Guide. See also Capacitor Failure Symptoms.
Related pages
[edit | edit source]- TRS-80 Model 16
- TRS-80 Model 16 Troubleshooting Guide
- TRS-80 Model 16 Capacitor Replacement Guide
- TRS-80 Model II General Maintenance
- Radio Shack TRS-80 Model 16 Service Manual
References
[edit | edit source]- ↑ Radio Shack, TRS-80 Model 16 Service Manual, catalogue numbers 26-6001/2, 1982, hosted as File:Radio Shack TRS-80 Model 16 Service Manual (26-6001, 26-6002, 1982).pdf. Introduction, p. 5.
- ↑ 2.0 2.1 2.2 TRS-80 Model 16 Service Manual (1982), mechanical parts list, pp. 70-73.
- ↑ 3.0 3.1 3.2 Ira Goldklang, "TRS-80 Troubleshooting Guide and Repair Q&A", Ira Goldklang's TRS-80 Revived Site (retrieved 2026-10-21). "All Models" section: "CRTs", "Power supplies", "Static".
- ↑ 4.0 4.1 4.2 4.3 TRS-80 Model 16 Service Manual (1982), Section 1, "Technical Specifications", pp. 7-10.
- ↑ 5.0 5.1 TRS-80 Model 16 Service Manual (1982), Section 3, "Troubleshooting", pp. 37-40.
- ↑ "TRS-80 Model II", Wikipedia (retrieved 2026-10-21). Section "Model 16".
- ↑ Radio Shack, TRS-80 Model 16B Built-in Hard Disk System Manual, 1983, hosted as File:Radio Shack TRS-80 Model 16B Built-in Hard Disk System Manual (1983).pdf. Chapter 9, "Maintenance", p. 38; Appendix D, "Specifications", p. 61.