DiBoss LT-32HLFH, Service Manual

Page: 69 / 73

2.1.1.4. Recommended Workarounds for VCT 49xyI-F1
Although the field problems have been fixed successfully, there are recommendations for specific input-signals.
Please consider the following table.
Hsync Distortion Malaysia Speed up DRX video AGC:
- KI_CHANGE_TH=1
- VAGC_REDUC=1
none previously
forced val-
ues now
default remove WA
Color Sensitivity,
bar edge distortion
RC: default
NOISE_BS=15
too high
India,
Malaysia Reduce NOISE_BS to 8
(partly adaptively when
chroma level is small)
Measured
Video S/N
1-2dB
smaller unchanged
(0xF still
default) keep WA
No. Issue Workaround for F1 Side-Effect Plan for F2
W1 Imbalance control can cause prob-
lems when changing from high to
low RF signal levels If TAGC_I = 0:
- set MOD_Ir = 0
- set MOD_If = 0
- write MOD_ACCU_BS = 0
(consider also W2)
none under inves-
tigation
W2 MOD_ACCU_BS must be written
several times until value is accepted Write MOD_ACCU_BS until readback
value matches written value (remember
that MOD_UPDATE has to be 1 for writ-
ing MOD_ACCU_BS) none firmware
redesign
W3 FM radio not working; root cause:
fast carrier recovery is automatically
ON in FM radio mode, should be
OFF Set PHAC_PB to 1 in FM radio mode
only, to 0 in TV modes none firmware
redesign
W4 When switching to FM-Radio mode
the output frequency sometimes will
not be set correctly Repeat switching to FM-Radio mode
and subsequently read out AFC_DEV
until the value is 0 none firmware
redesign
W5 Reduction of NICAM sensitivity at
weak RF signal conditions Set PHAC_PB to 1 in NICAM audio
mode none under inves-
tigation
No. Problem Countries Workaround
for C7 / Dx Side-Effect Status in F1 Recommen-
dation for F1
CIRCUIT DESCRIPTIONS