D Board Deflection Section - Sony D98 chassis Operation Manual

D BOARD DEFLECTION SECTION

1. Horizontal Deflection Circuit
Overview
These circuit drive the DY(Deflection Yoke) for Horizontal Deflection. The H size and H shape control (IC805 and around) is
included in this page as well.
H Drive, H Out, Feedback
HD pulse supplied from N board is inverted by Q501 and switch Q504 through Q502,503. The drive current which
introduced in HDT by this switching will drive Q505(H OUT) and 1000v pulse appears on collector. D504 is the "Damper
Diode" which avoid the negative pulse and discharge the energy for next Horizontal Drive. Q514 is the buffer for the "H
FBP" feed back to N board and it will be the reference of phase/jitter control of DSP. T504( HST) is to sense the deflection
current going to DY. The voltage appeared on secondary side will be the feed back for H Size/Shape control.
H Size/Shape control
HD pulse also triggering the H Size/Shape control IC805 (pin#8). IC805 is "PWM IC" and it controls H and HV B+
chopper duty. H Shape coming from N board is already including the Size Information(DC Level). It will be supplied to
IC805 (pin#2) after pulled up to 12V through R813. H Reg Output(pin#20) is switching pulse of Q506(B+ chopper). The
energy supplement from 180v to H Def circuit (through T502) is controlled by the duty of this pulse. The H Shape input
and feedback voltage(pin#20) from T504 are compared by error amp (in IC805) and H Reg out pulse duty is controlled to
keep the level of these two the same.
Troubleshooting
See attached "FLOW CHART" and confirm if it's really H Deflection issue.
No H Deflection / No Power
Check Q505, Q506 and D504 first. In case any of these shorted, check T501, Q504, R507 and D502.
Those parts might have been damaged.
If both of Q505, 506 were not broken, check the HD pulse at the gate of Q504.
If no pulse, check Q502, Q503, Q504.
Otherwise, check R512, D503 or try changing IC801.
Bad Distortion
Check pin#2 of IC805 and confirm that proper DC level and AC waveform.
If the distortion is on only right side, check all above ("No H Deflection").
Otherwise, refer to the Troubleshooting of next section ("H Lin and Ringing Correction").
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