ST750 GENERAL HANDBOOK
667/HB/33750/000 Page 109 Issue 6
P/Bus Init...
Bad L/S Cards
Once initialised, the phase bus processor performs more thorough checks on the
lamp switch card and may detect faults.
• Checks the monitor validation signal:
M/V Test ....Failed
Mon Val Failed
The monitor validation signal is generated by the main processor to check the phase
bus processor, so a failure is probably due to a faulty processor card.
• Step 1 Complete, Start Step 2:
At this point, the self-test has successfully checked-out the logic side of the cards. It
then displays a scrolling pattern on the amber LEDs to show that the first part of the
self-test is complete.
This pattern remains until the operator presses the level 3 button to confirm that the
self-test may switch on the lamp supply and continue its tests.
After the level 3 button is pressed, self-test switches on the lamp supply.
Towards the end of this second sequence of tests, it tests all the triacs by switching
each one on in turn for a very short period of time.
If standard HI 12V halogen lamps are used (with a transformer in the signal head),
then this pulse will not be seen on the street and so the signals need not be
covered. However it may be possible to see the pulse on lamps that are not driven
by any transformer, i.e. that run directly off the 240V.
If in doubt, all non-HI signal heads, i.e. 240V lamps, LED
Signals and 48V ped signals, should be covered before
proceeding any further with the self-test.
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