Z88 Service Manual
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The system test is carried out with the repaired Z88, in its case, mounted on a test frame. The full test equipment required is set out in the table below:

EquipmentSpecification/ManufacturerItem No.
Sinclair Spectrum Mains AdaptorCambridge Computer1
Z88 Cased Unit Test FixturesCambridge Computer2
Special Test Box (with separate power supply)Cambridge Computer3
Test Card Connector for SKT2Cambridge Computer4
Test Card Connector for SKT3Cambridge Computer5
Test Card Connector for SKT4Cambridge Computer6
Test Card for Peripheral Expansion ConnectorCambridge Computer7
RS232 Termination ConnectorCambridge Computer8
Standard RAM PackCambridge Computer9
Special Modified 32K RAM PackLocal modification10
128K EPROM Test Program PackCambridge Computer11
240 V Variable Transformer (with flying mains socket attached)Local Purchase12
Adaptor Test BoxCambridge Computer/Local manufacturer13

Preparation for Test

Before commencing the test verify the following:

  1. A gap exists between the case and the Reset switch.
  2. The Flap switch button is depressed and released when the flap is opened and closed.
  3. The adaptor is connected to the mains and its jack plug is inserted in the test box.
  4. The two banana fly leads from the test box are connected to the test fixture.

Test Functions

The system test exercises all the Z88 functions and by use of screen prompts progresses through six defined states. The software test is followed by a comprehensive test of all power functions, including current drain in the operational and coma states and a check of the 'supercap' operation.


  1. Set Switch B on the test fixture to position 2 (jack).
  2. Connect up the test rig as shown in Figure 3.1.
  3. Place the cased unit for test in the test fixture and slide the arms outward and down to lock it into position.
  4. Insert the special test card (Item 7) into the peripheral expansion slot and check that the LED is always ON. Remove test card.
  5. Insert the special test card (Item 3) into slots 1, 2 and 3 in turn and check that for each slot the LED is always ON.
  6. Remove the special test card from slot 3, leaving the flap open.
  7. Insert the jack plug from the test box (Item 2) into the jack socket of the unit under test.
  8. Close the flap and press the reset button (it may need to be pressed two or three times). Check that the display comes on showing the INDEX screen.
  9. Carry out the following:
  10. Press the RESET button on the unit and follow the screen prompt to check the following:
  11. At the end of the test check that TEST COMPLETE is displayed on the screen.
  12. Open the flap and check that the display goes OFF.
  13. Remove the software cards from slots 1, 2 and 3 and close the flap.
  14. Press the Reset button and check that the display comes ON.
  15. Set switch B on the test box to position 1 and check that the display remains ON.
  16. Remove the jack plug from the unit and check that the display remains ON.
  17. Tap the unit a few times and check that this has no effect on the display screen, ie no screen flickering etc.
  18. Open the flap and check that the display goes OFF.
  19. Close the flap and check that the BAT LOW (battery low) indication is NOT displayed on the screen.
  20. Set switch A on the test box to position 2 and release. Check that the BAT LOW indication is displayed on the screen.
  21. Carry out the following:
  22. Press both SHIFT Keys simultaneously to put the Z88 into the coma state.
  23. Carry out the following:
  24. Press both SHIFT keys simultaneously and check that the display comes back ON.
  25. Carry out the following:
  26. Carry out the following:

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Introduction to system test System test Adaptator test