Fault Check Procedures
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SECTION 2 FAULT FINDING AND SETUP
1
PRIMARY FAULT CHECK PROCEDURE
The following checklists should aid fault finding on the P4428 camera
to enable simple faults to be remedied and if necessary complete
boards changed. After a board or tube change the camera must be
electrically set up following the procedures detailed on pages 34 and
35.
For working on the camera the following basic skills are assumed :-
1)
The ability to use and interpret the results from an
oscilloscope.
2)
Some familiarity with a correctly working P4428 camera.
3)
Knowledge of basic camera operation and terminology.
The following facilities are assumed :-
1)
A Video Monitor capable of reproducing 625 line 50Hz
pictures (525 line 60Hz for USA) with 75
Ω
video input.
2)
A Dual Trace oscilloscope with X10 probes and a
multimeter (AVO or similar).
3)
A 1A 12V dc current limited supply with a means of
measuring supply current.
The following checklists are designed so as to locate the possible area
in which the fault lies based upon the easily observed or measured
fault conditions. For more detailed examination of faults these
checklists refer to “flow diagrams” and waveforms located in the rear
fold section of this manual. Page numbers to which these refer will be
given in the lists.
When working through the checklists the following points should be
noted :-
1)
Keep a note of each waveform checked and the reason, if any,
why if failed to correspond to the given waveform.
2)
The checklists are designed to locate single faults, multiple
problems may require working through the checklists several
times.
3)
A suitable thermal scene for testing purposes is an anglepoise
bench lamp, with a low voltage bulb (25-40W), pointed away
from the camera, so that the heated metal shade and arm of the
lamp provide a heat image against the general (cool)
background. Small point sources of heat should not be used
(soldering irons, naked flames etc) since if a fault in the iris
circuit exists permanent damage to the tube may result.
