Amstrad PCW 8512 Troubleshooting Guide
The Amstrad PCW 8512 is a Amstrad PCW 8256 with a second, double-sided drive and 512K of memory. Start-up, power supply, monitor, keyboard and printer faults are the same on both machines and are covered in the Amstrad PCW 8256 Troubleshooting Guide. The faults below are the ones only the 8512 can have: drive B, its discs, and the upper bank of memory.[1]
Warning: the drives sit in the monitor unit beside the mains power supply and the CRT. See the CRT Discharge Procedure before opening it.
Disc errors in drive B
[edit | edit source]Most drive B "faults" are discs used in the wrong drive. Drive B writes double-density CF-2DD discs and reads both sides at once, so a disc must go in with side 1 nearest the screen.[2]
| Symptom | Probable cause | Action |
|---|---|---|
| "Disc unsuitable", "Disc I/O" or "File non-recoverable" | Disc used in a drive that cannot handle it | A CF-2DD disc made in drive B cannot be read or written in drive A. Drive B can read a CF-2 disc made in drive A but must not write to it.[2] |
| Drive B disc reads as the wrong data, or not at all | Disc inserted the wrong way round | Insert drive B discs with side 1 nearest the screen. For a CF-2 disc from drive A, the side to be read goes nearest the screen.[2] |
| New disc not recognised in drive B | Not formatted for drive B | Format it in drive B with DISCKIT, from side 2 of the system disc.[2] |
| Motor runs but the disc does not turn | Perished belt | See drive belt.[3] |
Users found that ordinary CF2 discs work in drive B in place of CF2DD discs.[3] Amstrad's soft error advice applies to both drives: re-read a failing track ten times or more, step off the track and back, and only then suspect the drive.[1]
Amstrad's flow charts for drive B
[edit | edit source]The service manual's drive flow charts cover both drives, with the drive B (FD2) figures in brackets, and the seek error chart is for FD2 only. Amstrad marks them "for information only"; during the warranty period faulty mechanisms went back to Amstrad, and the second drive was always to be exchanged, never repaired.[1]
Seek error (FD2)
[edit | edit source]The chart on p. 9 runs as follows:[1]
- With the power off, turn the stepper motor rotor by hand. If the head slider does not move back and forth, replace the drive.
- With the power on, turn the rotor again. It should lock every 30 degrees. If it does not, replace the stepping motor.
- Watch the stepper move. If it does not move securely, check for step pulses at pins 10, 11, 14 and 15 of IC2 on the drive board: pulses present means replace the stepping motor; no pulses means replace the control board.
- If the stepper moves but the head does not stop at track 00, check that the track 00 sensor responds (the output of IC3 changes with the reflector). If it does, adjust the sensor's position; if it does not, replace the track 00 sensor assembly.
- If the head stops at track 00, measure TP5: it should be at least 4.5 V at track 00 and no more than 0.5 V at track 2. If it is, adjust the head position; if not, adjust the track 00 sensor position.
Read signal
[edit | edit source]Drive B's head output on track 79 of the EME-CF2DD test disc should be at least 70 mV peak to peak, measured between TP1 and TP2 with TP3 and TP11 as ground. Clean the head before measuring; Amstrad replaces the head if the output stays low.[1] The full drive B alignment figures are in the 8512 maintenance guide.
Memory
[edit | edit source]An 8512 has 512K, of which 368K is the RAM disc, drive M:.[1] If drive M: is the size an 8256 would give, about 112K, the machine is not using its upper 256K. Check that IC112–IC119 are fitted and seated, and that the memory links are set for 512K: A off, B on, C off, D on.[1] The upper eight DRAMs are TMM41257P-15 parts, the same type as IC104–IC111.[1] Amstrad's service manual has no memory test; its diagnostics were in the R.P.3 tool.[1]
Related pages
[edit | edit source]- Amstrad PCW 8512 · Amstrad PCW 8512 Maintenance Guide · Amstrad PCW 8256 Capacitor Replacement Guide
- Amstrad PCW 8256 Troubleshooting Guide
- Floppy Drive Repair · CRT Discharge Procedure
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Amstrad, PCW 8256/8512 Personal Computer Word Processor Service Manual. Hosted as File:Amstrad PCW 8000 Series Service Manual.pdf, described at Amstrad PCW 8256 / PCW 8512 Service Manual. Specification p. 2 (368K RAM disc); notes to service engineers p. 3; software errors p. 4; drive flow charts pp. 5–9, seek error chart for FD2 only p. 9; alignment checks pp. 11–14; PCW8512 parts list p. 34 (PDF p. 35); memory options table (PDF p. 36).
- ↑ 2.0 2.1 2.2 2.3 Amstrad, The PCW8256 and PCW8512 User Guide and Guide to Locomotive Software's LocoScript (AMSOFT, 1985). Hosted as File:Amstrad PCW8256 PCW8512 User Guide (1985).pdf, described at Amstrad PCW 8256 / PCW 8512 User Guide. Part III, Two-Drive Operation, pp. 1–8.
- ↑ 3.0 3.1 Richard Lloyd, PCW article ("Fifty two years and counting"), Amstrad CPC User Club Magazine (ACUC) issue 1, June 2022. Scan at archive.org. Retrieved 2026-10-02. The perished drive belt as the most common PCW fault; drive B double-sided and 720K; CF2 discs used in drive B.