Sony KP 48S70, Training Manual

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In the RA-2 chassis a vertical parabola signal is output from IC301/31 to
IC501/9. (See Waveform “A”)
At IC501 H pulses at pin 8 are pulse width modulated by the vertical
parabola signal at pin 9. The result is output to and amplified by Q505.
When the above signal (Waveform ‘B”) is applied to T502 PMT and
T503 HLT it controls the return path of the horizontal yokes by inducing
a voltage that causes more or less current to flow in accordance with
the waveform. This keeps the sides of the picture straight.
Centering
It should be noted here that centering of the horizontal yokes is done by
using one of the secondary coils of FBT T504 and attaching its center
tap to the return of the Green yoke. The other windings are connected
through rectifiers to the other yokes. Horizontal centering is necessary
because the red and blue tubes are at opposite angles to the screen in
reference to the green tube which is straight. Therefore by applying DC
voltages of opposite polarities with reference to the center tap we are
centering red and blue to green. If you place the negative lead of your
DVM to pin 8 of T504 FBT and the positive lead on D514 Cathode or
D515 anode you should read +4V and -4V respectively.
“A”
2v
5ms “B”
1v
5ms
High Voltage Development
High voltage is developed by taking the horizontal output pulses and ap-
plying them to the Flyback Transformer T504. The Flyback Transformer
T504 steps up the horizontal pulses and rectifies them. This produces
31Kv at its output. This voltage goes to the high voltage block where it is
distributed to the three picture tubes.
This is where the RA-2 chassis differs from the previous Sony projection
television sets. This chassis has no high voltage regulation. However there
have been various steps taken to compensate for this fact.