2. 32k RAM PACK MODIFICATION
In order to modify a standard 32k RAM pack to produce a test pack for use in System Test, certain wiring must be connected from the chip to the card connectors as follows:
|32k RAM Chip||Card Connector|
|A12 (pin 2)||wire to A17 (pin 36)|
|A13 (pin 26)||wire to A18 (pin 37)|
|A14 (pin 1)||wire to A19 (pin 38)|
Figure A.1 - PSU FOR TEST FIXTURE
NOTE: Output is as follows depending on the position of switch A:
- Position 1 - 2.8V
- Position 2 - 3.8V to 4.6V
- Position 3 - 4.6V to 6.1V
Figure A.2 - RS232 LOOPBACK TEST PLUG
- The principal aim is to check that every wire is connected to the 9-way socket including the 10M between pin 1 and the socket frame.
- For the serial port to work, both CTS and DCD must be high.
Figure A.3 - CARD TESTER CIRCUIT FOR SLOT CONNECTORS AND BUS EXTENSION CONNECTOR
- The 'test head' of both the slot connector tester and the bus extension connector tester use the above circuit.
- The LED is connected between pins 4 and 5 on the test connector test head.
- A 0.4 mm thick spacer is installed between the connector side of the pcb and the plastic housing. This builds in a deliberate spacing so that the test pcb will only make contact provided all 38 connector springs are positive.
- The Z88 mains adaptor is connected for the slot connector tester and the Spectrum adaptor is connected for the bus extension tester.
Figure A.4 - SLOT TESTER TEST HEAD CIRCUIT DIAGRAM
- There is no R16 or D16 connected.
- All resistors are 1 Mohm, all diodes lN4148.
Figure A.5 - BUS EXTENSION TESTER TEST HEAD CIRCUIT DIAGRAM
- Slot is in pin 18 position.
- Side A of the connector is the component side.
- All resistors are 1 i10hm, all diodes lN4148.
- GND goes to connector pi n A14.
- Sense connections are made to all except pins A14, B1 and B24.