The Ra-3/3A Chassis - Sony KDP-57XBR2 Training Manual

1. Features
Chapter 2 - The RA-3/3A Chassis
Overview
The RA-3 chassis introduced a major redesign in the convergence circuits that made it much easier for the
TM
technician to converge the set with greater accuracy and speed. It is know as Flash Focus and allowed the
customer to perform more thorough convergence realignment should it drift out of range. The RA-4 was actually
the first unit to introduce this feature a year earlier, but it was confined to the more expensive XBR200 series
units. The RA-3 brought this feature to the more affordable models.
The power supply still utilized the dual transistor switching power supply that is found in previous sets, and
incorporated the two transistors into a single IC package. A separate standby supply still exists but uses a FET
transistor for switching instead of a bi-polar type. Self-diagnostics were also introduced to aid in troubleshooting.
The number of circuit boards was substantially reduced with most of the circuits residing on the A and G boards.
The G board now contained the deflection circuits, along with the usual power supply components rather than
utilizing a separate D board. Unlike previous sets, which had a separate horizontal scan and high voltage
sections, the horizontal/HV is handled with a single output and flyback to generate H scan and HV. This makes
deflection and HV problems easier to diagnose. The A board handles video processing, system control and the
TM
Flash Focus circuit. Pincushion correction was simplified by substantially reducing the number of discrete
components.
The RA-3 also provided the customer with component video capability, which was previously found only on the
XBR series. The T and S series models provided a single component input at the rear in the video 4 slot while the
V series provided for two components inputs at video 4 and 5.
There are not any significant differences between the RA-3 and RA-3A worth mentioning. In fact, the circuits are
almost identical with some minor design changes. The RA-3A chassis was simply a carry-over into the next
model year, so the troubleshooting procedures remain the same for both. To keep things simple, only the RA-3
in the titles and text portions of this section will be mentioned.
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