Acorn Risc PC 700 Troubleshooting Guide: Difference between revisions
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[[File:Acorn Risc PC 700 (photo).jpg|thumb|right|300px|Acorn Risc PC 700. Source: Wikimedia Commons.]] | |||
This guide gives diagnosis for the '''[[Acorn Risc PC 700]]''' (ARM710, board 1208,000). The Risc PC 700 shares its diagnostics with the [[Acorn Risc PC 600 Troubleshooting Guide|Risc PC 600]]: the same Power On Self Test (POST), the same IOMD/VIDC20/FDC37C665 chipset, the same on-board fuses, and the same surface-mount-electrolyte failure mode. The differences are the 40 MHz ARM710 CPU card and RISC OS 3.60. The POST and parts/electrical data are in the [[Acorn Risc PC Technical Reference Manual]], which also holds the circuit diagrams.<ref name="trm">[[Acorn Risc PC Technical Reference Manual]] (Issue 1, September 1994; part 0497,057), Acorn Computers — hosted on this wiki. Source for the Power On Self Test and fault/status codes, the on-board fuses FS1 (2 A) and FS2 (800 mA), the NiMH battery, the IOMD/VIDC20/FDC37C665 architecture and the engineering drawings. The TRM documents the original 0197,000 board; the 700's 1208,000 board is a revision.</ref> | This guide gives diagnosis for the '''[[Acorn Risc PC 700]]''' (ARM710, board 1208,000). The Risc PC 700 shares its diagnostics with the [[Acorn Risc PC 600 Troubleshooting Guide|Risc PC 600]]: the same Power On Self Test (POST), the same IOMD/VIDC20/FDC37C665 chipset, the same on-board fuses, and the same surface-mount-electrolyte failure mode. The differences are the 40 MHz ARM710 CPU card and RISC OS 3.60. The POST and parts/electrical data are in the [[Acorn Risc PC Technical Reference Manual]], which also holds the circuit diagrams.<ref name="trm">[[Acorn Risc PC Technical Reference Manual]] (Issue 1, September 1994; part 0497,057), Acorn Computers — hosted on this wiki. Source for the Power On Self Test and fault/status codes, the on-board fuses FS1 (2 A) and FS2 (800 mA), the NiMH battery, the IOMD/VIDC20/FDC37C665 architecture and the engineering drawings. The TRM documents the original 0197,000 board; the 700's 1208,000 board is a revision.</ref> | ||
Revision as of 12:51, 16 July 2026
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This guide gives diagnosis for the Acorn Risc PC 700 (ARM710, board 1208,000). The Risc PC 700 shares its diagnostics with the Risc PC 600: the same Power On Self Test (POST), the same IOMD/VIDC20/FDC37C665 chipset, the same on-board fuses, and the same surface-mount-electrolyte failure mode. The differences are the 40 MHz ARM710 CPU card and RISC OS 3.60. The POST and parts/electrical data are in the Acorn Risc PC Technical Reference Manual, which also holds the circuit diagrams.[1]
⚠️ Mains warning
The Risc PC 700 has a fan-cooled mains PSU in the base slice. Disconnect the mains lead before removing the cover; the PSU primary side is at mains potential and the module should not be opened unless you are competent with mains switch-mode supplies (discharge the primary bulk capacitor first).
Power On Self Test (POST)
The 700 runs the same POST as the 600. Progress is shown by the screen colour, and a failure is signalled on screen (red) and by the floppy-disc LED flashing an 8-digit hexadecimal fault code (long flash = 1, short flash = 0).[1]
Normal sequence: purple (brief ROM/RAM tests, then IOMD and VIDC20 init and test — a crash here indicates a major I/O fault) → screen mode set from the video ID[0] pin (VGA or 15 kHz TV mode; no stable display means a monitor, video or fundamental fault) → blue (extensive memory test, then video and sound tests) → purple (ARM ID read; needs good RAM) → green (pass; RISC OS starts and shows a black screen with the memory-size message) or red (fail; floppy LED flashes the code).
| Code | Meaning | First-look |
|---|---|---|
| 00000200 | ROM failed checksum | Reseat/replace the RISC OS 3.60 ROMs |
| 00001000 | IOC register test failed | IOMD or its bus |
| 00004000 | VIDC (Virq) timing failed | VIDC20 or its clock/interrupt path |
| 00008000 | Sound (Sirq) timing failed | VIDC20 16-bit sound path |
| 00010000 | CMOS unreadable | I²C path to CMOS/RTC; battery circuitry |
| 00020000 | RAM control line failure | Classic leaked-electrolyte symptom — recap and repair corroded RAM-control tracks; reseat SIMMs |
| 00040000 | Long RAM test failure | Faulty SIMM; substitute |
Informational status bits include 00000040 (integrated I/O fitted), 00000080 (VRAM present — standard on the 700) and 00000100 (CMOS checksum error). A POST interface box on the parallel port shows the tests and a PASS/FAIL bitmap on an LCD.[1]
Diagnostic flow
- Completely dead: check the mains-plug fuse; with the lid open, confirm the PSU rails and fan; check on-board fuses FS1 (2 A) and FS2 (800 mA) for continuity.[1]
- Crashes early / RAM-control fault (00020000): inspect the board for leaked surface-mount electrolyte and corroded RAM-control tracks; recap and clean; reseat SIMMs and the VRAM.
- Red screen + LED code: decode the 8-hex code (table above).
- No display: try a known-good monitor; check the VGA connector and the video ID pin; verify VIDC20.
- Won't start with a second CPU/PC card: retest with only the primary ARM710 card, reseated.
Symptom table
| Symptom | Probable cause | Action |
|---|---|---|
| Completely dead | Mains fuse, PSU, or on-board fuse | Check plug fuse, PSU rails/fan, FS1/FS2 |
| Crashes early (purple) / RAM-control fault | Leaked electrolyte or bad SIMM | Recap and clean; reseat/substitute SIMMs |
| Red screen, floppy LED flashing | POST fault — read the code | Decode the LED code |
| No stable display | Monitor/cable, video ID pin, VIDC20 | Try another monitor; check VGA; verify VIDC20 |
| Lost configuration / wrong clock | Flat or leaked NiMH battery (BT1) | Clean, repair tracks, replace cell |
| No / distorted sound (00008000) | VIDC20 16-bit sound path or leaked caps | Recap; check the sound path |
| Hard disc not found | IDE cable/power or dead drive | Reseat the cable; replace the drive |
| One subsystem dead, rails present | Blown on-board fuse | Check FS1/FS2 |
Always suspect leaked electrolyte
As on the 600 and the Acorn Archimedes A5000, intermittent and progressive Risc PC faults are frequently leaked surface-mount electrolytic capacitors rather than a failed IC, and the POST "RAM control line failure" code points straight at corroded RAM-control tracks. Inspect under magnification and recap before deeper diagnosis — see Acorn Risc PC 700 Capacitor Guide.
Storage and ports
- Hard disc not detected: check the 40-way IDE cable and drive power. RISC OS 3.60 supports discs larger than 512 MB.
- Floppy: clean the head and try a known-good disc before suspecting the FDC37C665.
- Serial/parallel: handled by the FDC37C665.
- Expansion: clean the podule backplane and network-card contacts.
Related pages
- Acorn Risc PC 700
- Acorn Risc PC 700 Maintenance Guide
- Acorn Risc PC 700 Capacitor Guide
- Acorn Risc PC 600 Troubleshooting Guide — the near-identical 600 procedure
- Acorn Risc PC Technical Reference Manual · Capacitor Failure Symptoms
References
- ↑ 1.0 1.1 1.2 1.3 Acorn Risc PC Technical Reference Manual (Issue 1, September 1994; part 0497,057), Acorn Computers — hosted on this wiki. Source for the Power On Self Test and fault/status codes, the on-board fuses FS1 (2 A) and FS2 (800 mA), the NiMH battery, the IOMD/VIDC20/FDC37C665 architecture and the engineering drawings. The TRM documents the original 0197,000 board; the 700's 1208,000 board is a revision.