Service manual

Chapter 5 E20 Fault finding
FileStore Service Manual 48
The hard disc unit:
+5V around 1 to l.5A
+12V up in 4.5A, falling to around 2A when up to speed.
Host Adaptor board:
+5V around 500mA
+12V zero (not used)
The above figures are approximate and will enable checks to be made for open/short circuits and
malfunctioning components.
5.2 Address decoding
To test the address decoding, execute a program to access the relevant memory location. This is
done by the SCSI interface tests in the FServTest program of the FileStore test software. See
Appendix A – Test Equipment at the back of this manual for further details.
5.3 Hand shaking
To test the SEL/BSY handshake, use the handshake test of the SCSI interface tests in the FservTest
program of the FileStore test software. See Appendix A – Test Equipment, for further details.
5.4 Bus lines
When the buses are not being asserted by the host system, i.e. in the bus free phase, all bus lines
will float according to the values of their terminating resistors.
Measure the voltage of each bus line in turn and make sure that none of them is stuck at +5V, which
would indicate a short circuit, or at 0V, which would indicate that there was a short circuit. The
correct voltages are as follows:
2 MHz expansion bus D0 to D7 and A0 to A7 should all be 2.5V.
If for example, D0 to D7 are all at 0V or a mixture of 0V and 2.5V, then one of the buffers is
probably enabled.
5.5 Final checks
If the procedures outlined above fail to uncover the fault, then as a final check you should refer to
Appendix A - Test Equipment, which contains more thorough tests of the FileStore.
The tests to run and the order in which to run them are as follows:
 Run all the tests in FServTest
 Run FServFmt on each disc
 Run PServInit on each disc
 Run FServSoak, running all the test patterns on each disc.