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Chapter 2—Functional Descriptions
Model 330, 340SC and 370SC Service Manual 2–3
WARNING!!!
The HJT Model 330, 340SC and 370SC
projectors use high voltages and high currents. Operation with
covers removed exposes personnel to these dangerous conditions
and may result in serious injury or death. No user-serviceable parts
are contained within the projector. Refer all maintenance to only
factory authorized and trained technicians.
The projector cover is a two-piece molded assembly. It is fastened to the projector
frame by six (6) screws: two (2) on the rear cover; and four (4) on the front cover.
The fan intake side of the cover (right side) has filters on the intake vents.
Periodic cleaning of the filters is required and should be performed in accordance
with the procedure in this manual (Section 4.3). To avoid overheating the
projector, ensure that the cover vent ports are free of obstructions at all times and
that an adequate supply of fresh air is provided to the projector during operation.
2.2 External Power Requirements
The projectors require 208V to 240V, 50 Hz to 60 Hz, single-phase AC power.
The units are equipped with an attached AC power cord and 3-prong twist lock
plug (Model 330 and 340SC use Hubble Model 2323; Model 370SC uses Hubble
Model 2623 or equivalent).
CAUTION!
Operation at voltages and frequencies outside of these
listed parameters may cause damage to the projector and will void the warranty.
2.3 Electronics Systems Overview
The objective of this portion is to provide a good general understanding of the
projector electronics. The understanding gained will enable service personnel to
more effectively maintain the projector to produce the desired result—a great
picture on the screen —and quality you can see.
The Electronics Systems portion of this manual is based on block diagrams. The
diagrams used have been drawn with two purposes in mind. First, they are general
enough to be able to gain an understanding of the overall function of the various
components of the system. Second, the block diagrams contain enough detail to
make them valuable as a troubleshooting tool should the need arise. Schematics
are not used but, where necessary, simplified circuitry is shown to aid in
understanding the capabilities and/or limitations of the system. Discussion of
troubleshooting is included but is largely confined to symptoms and identification
of failed assemblies.
The Hughes-JVC Model 330, 340SC and 370SC projectors are multi-sync
projectors capable of data, graphics, and display from 15KHz to 90KHz