Acorn Risc PC 700 Maintenance Guide: Difference between revisions
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This guide covers preventive maintenance for the '''[[Acorn Risc PC 700]]''' (launched July 1995). The 700 is an ARM710 machine that shares the Risc PC architecture and slice case with the [[Acorn Risc PC 600]]; the differences are the faster 40 MHz CPU card, RISC OS 3.60, VRAM and 16-bit sound as standard, and the revised '''1208,000''' main board. The maintenance priorities are the same as the 600: the '''mains PSU''', the '''NiMH backup battery''', and the leak-prone '''surface-mount electrolytic capacitors'''. | This guide covers preventive maintenance for the '''[[Acorn Risc PC 700]]''' (launched July 1995). The 700 is an ARM710 machine that shares the Risc PC architecture and slice case with the [[Acorn Risc PC 600]]; the differences are the faster 40 MHz CPU card, RISC OS 3.60, VRAM and 16-bit sound as standard, and the revised '''1208,000''' main board. The maintenance priorities are the same as the 600: the '''mains PSU''', the '''NiMH backup battery''', and the leak-prone '''surface-mount electrolytic capacitors'''. | ||
== | == Safety: mains PSU == | ||
The Risc PC 700 has a fan-cooled mains switch-mode PSU in the base slice. Disconnect the mains lead before removing the cover, and never work on the supply while it is plugged in. '''The PSU primary side and its reservoir and mains-suppression capacitors can hold a lethal charge after the machine is unplugged — a shock can be fatal.''' The module can be opened and recapped as part of a restoration, but only if you are competent with mains switch-mode supplies: discharge the reservoir capacitor and confirm 0 V before touching the primary side. Observe anti-static precautions for the CPU card, IOMD, VIDC20, ROMs, SIMMs and VRAM. | The Risc PC 700 has a fan-cooled mains switch-mode PSU in the base slice. Disconnect the mains lead before removing the cover, and never work on the supply while it is plugged in. '''The PSU primary side and its reservoir and mains-suppression capacitors can hold a lethal charge after the machine is unplugged — a shock can be fatal.''' The module can be opened and recapped as part of a restoration, but only if you are competent with mains switch-mode supplies: discharge the reservoir capacitor and confirm 0 V before touching the primary side. Observe anti-static precautions for the CPU card, IOMD, VIDC20, ROMs, SIMMs and VRAM. | ||
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A broken front-flap spring (a cosmetic sag of the front flap) is common and does not affect operation. | A broken front-flap spring (a cosmetic sag of the front flap) is common and does not affect operation. | ||
== | == NiMH backup battery and capacitor leakage == | ||
The 700 uses the same on-board '''NiMH backup cell (BT1, 1.2 V)''' and the same surface-mount aluminium electrolytic capacitors as the 600.<ref name="trm">[[Acorn Risc PC Technical Reference Manual]] (Issue 1, September 1994; part 0497,057), Acorn Computers — hosted on this wiki. Documents the Risc PC architecture (IOMD, VIDC20, FDC37C665), the on-board fuses FS1 (2 A) and FS2 (800 mA), the NiMH battery, the main-PCB parts list and the Power On Self Test. The parts list covers the original 0197,000 board; the 700's 1208,000 board is a revision.</ref> Both leak with age. Inspect BT1 and the surface-mount electrolytics for leaked electrolyte and corrosion; clean and repair, replace the battery, and recap the board. Full list and procedure: [[Acorn Risc PC 700 Capacitor Guide]]. | The 700 uses the same on-board '''NiMH backup cell (BT1, 1.2 V)''' and the same surface-mount aluminium electrolytic capacitors as the 600.<ref name="trm">[[Acorn Risc PC Technical Reference Manual]] (Issue 1, September 1994; part 0497,057), Acorn Computers — hosted on this wiki. Documents the Risc PC architecture (IOMD, VIDC20, FDC37C665), the on-board fuses FS1 (2 A) and FS2 (800 mA), the NiMH battery, the main-PCB parts list and the Power On Self Test. The parts list covers the original 0197,000 board; the 700's 1208,000 board is a revision.</ref> Both leak with age. Inspect BT1 and the surface-mount electrolytics for leaked electrolyte and corrosion; clean and repair, replace the battery, and recap the board. Full list and procedure: [[Acorn Risc PC 700 Capacitor Guide]]. | ||
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| NiMH battery (BT1) || Lost config/clock; corrosion || Clean, repair tracks, replace cell | | NiMH battery (BT1) || Lost config/clock; corrosion || Clean, repair tracks, replace cell | ||
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| Mains PSU module || Dead, random resets, fan/thermal issues || Check rails and fan; | | Mains PSU module || Dead, random resets, fan/thermal issues || Check rails and fan; recap the PSU (discharge first) or fit a known-good supply | ||
|- | |- | ||
| On-board fuses FS1/FS2 || A subsystem dead with rails present || Check FS1 (2 A) and FS2 (800 mA) continuity | | On-board fuses FS1/FS2 || A subsystem dead with rails present || Check FS1 (2 A) and FS2 (800 mA) continuity | ||