Sinclair ZX81 General Maintenance: Difference between revisions
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[[File:Sinclair ZX81 PCB Top.JPG|thumb|300x300px|Sinclair ZX81 Mainboard (Issue 2)]]Maintaining your Sinclair ZX81 ensures reliable operation and extends the life of this classic computer. This guide covers essential care, preventive steps, and troubleshooting for both Issue 1 and Issue 2 boards. | |||
Maintaining your Sinclair ZX81 ensures reliable operation and extends the life of this classic computer. This guide covers essential care, preventive steps, and troubleshooting for both Issue 1 and Issue 2 boards. | |||
'''Electrostatic Discharge (ESD) Warning:''' | '''Electrostatic Discharge (ESD) Warning:''' | ||
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<templatestyles src="Template:StyledTable/styles.css" /> | <templatestyles src="Template:StyledTable/styles.css" /> | ||
== Board Revisions == | |||
== | |||
{| class="wikitable styledtable" | {| class="wikitable styledtable" | ||
! Revision !! PCB Marking !! Key Differences !! Common Issues | ! Revision !! PCB Marking !! Key Differences !! Common Issues | ||
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|} | |} | ||
== | == Power Supply & Regulator Care == | ||
The ZX81 uses a linear power supply: | The ZX81 uses a linear power supply: | ||
* '''PSU Part:''' Sinclair 9V DC Adapter (center negative) | * '''PSU Part:''' Sinclair 9V DC Adapter (center negative) | ||
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* '''C7''' – Video circuit decoupling | * '''C7''' – Video circuit decoupling | ||
== | == Capacitor Replacement Table == | ||
{| class="wikitable styledtable" | {| class="wikitable styledtable" | ||
! Position !! Value (µF) !! Voltage (V) !! Notes !! Series/Type | ! Position !! Value (µF) !! Voltage (V) !! Notes !! Series/Type | ||
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|} | |} | ||
== | == Voltage & Clock Test Points == | ||
{| class="wikitable styledtable" | {| class="wikitable styledtable" | ||
! Test Point !! Pin/Location !! Expected Value !! Tolerance | ! Test Point !! Pin/Location !! Expected Value !! Tolerance | ||
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|} | |} | ||
== | == Essential Tools == | ||
* ESD wrist strap & mat | * ESD wrist strap & mat | ||
* Phillips and flat screwdrivers | * Phillips and flat screwdrivers | ||
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* Isopropyl alcohol & brush | * Isopropyl alcohol & brush | ||
== | == Preventive Maintenance Checklist == | ||
# Power off and unplug the ZX81. | # Power off and unplug the ZX81. | ||
# Remove case and visually inspect PCB for corrosion or damage. | # Remove case and visually inspect PCB for corrosion or damage. | ||
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# Reassemble and test basic operation. | # Reassemble and test basic operation. | ||
== | == Common Faults & Quick Checks == | ||
{| class="wikitable styledtable" | {| class="wikitable styledtable" | ||
! Symptom !! Likely Cause !! Quick Check | ! Symptom !! Likely Cause !! Quick Check | ||
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|} | |} | ||
== | == Troubleshooting Flowcharts == | ||
# '''No Power''' | # '''No Power''' | ||
## → Check PSU output → If OK, check 7805 output → If 5V missing, replace 7805 or C5/C6. | ## → Check PSU output → If OK, check 7805 output → If 5V missing, replace 7805 or C5/C6. | ||
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## → Inspect membrane for cracks → Clean edge connector → Replace membrane if needed. | ## → Inspect membrane for cracks → Clean edge connector → Replace membrane if needed. | ||
[[Category: Sinclair Computers]] | |||