Pincushion - Sony WEGA KV27FV15 Training Manual
Direct view
television circuit description and troubleshooting
Hide thumbs
Also See for WEGA KV27FV15:
- Operating instructions manual (42 pages) ,
- Service manual (36 pages) ,
- Operating instructions manual (42 pages)
Table of Contents
Advertisement
Pincushion
Overview
The purpose of the pincushion circuit is to correct for deflection distortion.
This distortion occurs because of the yokes inability to create a linear
beam scan. The result would be a picture bowed at the sides. We com-
pensate for this problem by using pincushion correction circuits to control
the amount of current that can flow through the horizontal output's return.
More current is delivered so the beam can be pushed to the sides of the
tube when necessary.
Circuit Description
The E/W signal from IC355/11 is input to IC501 Pin Control at its inverting
input. A sample of the ABL signal from T503/11 is also input to this same
input.
The main HP signal from C510 in the Horizontal Output section is applied
to R524. The signal is applied to a clamp that consists of D518, D523 and
D524. It is also applied to R525 and D516. This signal is now stripped of
its negative component and integrated by C530. This signal is then ap-
plied to IC501/5 non-inverting input. IC501 Pin Control compares the
inverting and non-inverting inputs and outputs their difference. The result
is output at IC501/7.
IC501/5 - .5V, 20us
IC501/6 - .2V, 5ms
IC501/7 - .5V, 5ms
35
This signal is then applied to the base of Q511 Pin Out. The signal is
inverted by Q511 and then input to the base of Q512. The result is that a
PWM waveform is seen at Q512/C. Q512/C is connected to the return for
the horizontal output. When Q512 Pin Out is conducting it allows more
current to be drawn by the horizontal yoke. The conduction of Q512 is set
up so that more current is drawn during the middle edges of the scanning
of a horizontal line. The result is shown where the output leaves this
circuit at R526.
The H Protect circuit will remove the horizontal drive signal if the HP pulses
are not input to IC501/5. This will also occur if Q511 or Q512 short.
Q512/B - 2V, 5ms
Q512/C - 50V, 20us
R526 - 100V, 5ms
Hide quick links:
Advertisement
Table of Contents
