Sinclair ZX Spectrum+ General Maintenance: Difference between revisions
Create ZX Spectrum+/+2 page set (service manuals + community repair sources, cited) |
P5 verification: correct figures and re-attribute the Repair Data citations to the T.I.S. document now hosted here; remove emoji headings |
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The maintenance priorities are the '''keyboard membrane and its clamped ribbons''', the '''7805 regulator and heatsink''', the '''edge connector''', and the ageing '''DC-DC converter''' that feeds the lower RAM. | The maintenance priorities are the '''keyboard membrane and its clamped ribbons''', the '''7805 regulator and heatsink''', the '''edge connector''', and the ageing '''DC-DC converter''' that feeds the lower RAM. | ||
== | == Safety == | ||
There are '''no mains voltages inside the computer''' — it runs from an external 9 V supply and the highest voltage on the board is +12 V. The mains transformer is inside the PSU brick, which can be opened and repaired (see below) by someone comfortable with mains wiring.<ref name="ian">Worsley, Ian. ''Repairing Spectrum & Spectrum Plus'', Lil Old Sinclair Technical Information Repository. Source for the PSU repair procedure, keyboard ribbon handling and Spectrum+-specific keyboard fixes, socket re-tensioning and the multimeter diagnostic approach.</ref> | There are '''no mains voltages inside the computer''' — it runs from an external 9 V supply and the highest voltage on the board is +12 V. The mains transformer is inside the PSU brick, which can be opened and repaired (see below) by someone comfortable with mains wiring.<ref name="ian">Worsley, Ian. ''Repairing Spectrum & Spectrum Plus'', Lil Old Sinclair Technical Information Repository. Source for the PSU repair procedure, keyboard ribbon handling and Spectrum+-specific keyboard fixes, socket re-tensioning and the multimeter diagnostic approach.</ref> | ||
Observe normal anti-static precautions for the ULA, Z80A, ROM and RAM.<ref name="sm48">''ZX Spectrum Service Manual'' | Observe normal anti-static precautions for the ULA, Z80A, ROM and RAM.<ref name="sm48">''ZX Spectrum Service Manual'', Sinclair Research Ltd. Source for the repair notes, the supply test points, the keyboard structure and the per-issue modifications. Hosted on this wiki as [[Sinclair ZX Spectrum Service Manual]] ([[:File:Sinclair ZX Spectrum Service Manual.pdf|PDF]]).</ref><ref name="tis">''ZX Spectrum Servicing Manual'', prepared by Thorn (EMI) Datatech Ltd for Sinclair Research Ltd, March 1984 — the '''Repair Data''' section, symptoms 1 to 14, added by T.I.S. (Technical Information Services). Hosted on this wiki as [[ZX Spectrum Servicing Manual (Thorn EMI Datatech, 1984)]] ([[:File:ZX Spectrum Servicing Manual Thorn EMI Datatech 1984.pdf|PDF]]). '''Third-party field-service material, not Sinclair's own text''', and absent from the re-typeset edition hosted as [[Sinclair ZX Spectrum Service Manual]].</ref> | ||
== | == The golden rule == | ||
'''Never plug or unplug anything into the expansion edge connector while the machine is switched on.''' This single habit is reported as the cause of '''80–90 % of Spectrum faults''': the keyway peg on the interface plug drops out with use, the connector shifts sideways, and the bus lines short together — taking out TR4 and often the RAM with it.<ref name="ian" /> | '''Never plug or unplug anything into the expansion edge connector while the machine is switched on.''' This single habit is reported as the cause of '''80–90 % of Spectrum faults''': the keyway peg on the interface plug drops out with use, the connector shifts sideways, and the bus lines short together — taking out TR4 and often the RAM with it.<ref name="ian" /> | ||
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The 7805 does all the heavy lifting and the Spectrum runs warm by design. | The 7805 does all the heavy lifting and the Spectrum runs warm by design. | ||
* Check the '''heatsink is tight and undamaged'''. The | * Check the '''heatsink is tight and undamaged'''. The Repair Data makes checking the heatsink the '''first''' step for any reported fault, and warns about over-tightened screws.<ref name="tis" /> | ||
* Look for '''hairline cracks in the board radiating from the heatsink screws''' — a documented cause of intermittent faults.<ref name=" | * Look for '''hairline cracks in the board radiating from the heatsink screws''' — a documented cause of intermittent faults.<ref name="tis" /> | ||
* Apply fresh thermal compound when refitting the regulator, and ensure good contact between the regulator body and the heatsink.<ref name="sm48" /> | * Apply fresh thermal compound when refitting the regulator, and ensure good contact between the regulator body and the heatsink.<ref name="sm48" /> | ||
* '''In normal running the ULA runs quite warm; every other IC should be cold.''' A warm RAM chip is a failing RAM chip.<ref name="ian" /> | * '''In normal running the ULA runs quite warm; every other IC should be cold.''' A warm RAM chip is a failing RAM chip.<ref name="ian" /> | ||