IOX® / DCX® Series UHF-TV Transmitter
Maintenance Manual
1.
IOX and DCX Performance Pyramids
The main section of this manual is based on a "performance pyramid" concept. The IOX
performance pyramid is shown in Figure 1 on the following page. The pyramid shows the
relational interdependence between the various procedures contained in this section. The
numbers in parenthesis indicate the service bulletin addressing the procedure described.
As in the case of a real pyramid, the stability of the upper levels depends on the levels below.
Accordingly, as per Figure 1, the filament, body, focus, bias, etc. meters should be properly
calibrated before the high voltage is activated and the crowbar test fired; the crowbar should be
successfully test fired before the high voltage is connected to the tube and the idle current
adjusted; the idle current should be correctly adjusted before IOT tuning is attempted, and so
forth.
By starting at the lowest levels of the pyramid and climbing progressively upwards, it possible to
perform a complete verification of the entire transmitter, as was done when the transmitter was
originally commissioned. When used in this manner, the pyramid can serve as a suggested
procedure for a yearly transmitter check-up.
During routine maintenance periods, the pyramid alerts the reader to possible consequences
from making a given adjustment. Generally speaking, an adjustment at a lower level in the
pyramid may require that many or all of the levels above it be readjusted (e.g. a change in the
aural power ratio may dictate a readjustment of the linearity & ICPM correctors, differential
phase & gain correctors, and aural carrier & B3 ICPM correctors).
The performance pyramid for the DCX series of ATSC transmitter is contained in Figure 2.
WARNING:
A television transmitter is a complex piece of telecommunications
equipment. Only properly qualified personnel should attempt any of the procedures
contained in this manual. Users should fully read and understand the intent and theory of
all
of the procedures contained in this manual, and the general principles of operation of
the entire transmitter, before attempting to make any adjustments.
Additionally, users should ensure that they have the required test equipement and/or
tools to complete a procedure before starting. IOX customers should consult Service
Bulletin 030626 for a list of recommended NTSC test equipment.
DANGER:
The IOX/DCX series of transmitters employ potentially lethal high voltage.
Proper high voltage safety precauations should be employed at all times when
performing the procedures contained in this manual. Please consult Service Bulletin
940911 for more details.
