Service Modes, Error Codes, and Fault Finding
EN 21LC4.31E AA 5.
input of the scaler) is only used for teletext. This means that no
mixed mode (video plus teletext simultaneously) is possible. If
there is sound and teletext, but no video and user menu (blank
screen), the digital path (Hercules - ADC - Columbus - Scaler)
is faulty. If there is sound but no teletext, the back-end part
(Scaler - LCD panel) is faulty. In Crystal Clear models, which
do not have an ADC and Columbus, the RGB path (analogue
input of scaler) is used for both video and teletext.
No TV, but PC is Present
1. Check if Hsync_SDTV and Vsync_SDTV are present at pin
1 & pin13 of 7E03.
2. If they are present, check teletext output.
3. If there is no teletext output, the IC TDA150xx may be
defect.
5.7.6 Power Supply
Check Fuse
The power supply (various models are used) contains one fuse
near the AC input connector X002.
1. Check with power supply in “off” state by means of ohmic
measurement.
2. Fuse X102 may open in case of severe lightning strikes
and/or failures in the power supply.
3. Check the standby signal at pin 10 of X200. ON is HIGH,
OFF is LOW. During standby mode only the 3V3 is present
at pin 10.
Protections Concept on Power Supply Board (two models)
1. 12 V output (pin 8 of X200): Short-circuit protected by 2.5
A fuse X610. Over-voltage protection when output voltage
is more than 40% above nominal value.
2. Vaudio output (+18 or +24 V, depending on power
supply model used); (pin 1 of X200): Short-circuit proof
(+18 V version has 2.5 A fuse X660). Over voltage
protection when output voltage is more than 40% above
nominal value.
3. 3V3STBY output (pin 3&4 of X200): Short-circuit proof
with auto-restart. Over voltage protection when output
voltage is more than 40% above nominal value.
4. 24 V output (for inverter X520 & X530): Short-circuit
proof with auto-restart. Over voltage protection when
output voltage is more than 40% above nominal value.
Standby Mode
1. Apply a 12 ohm load resistor of sufficient power rating to all
outputs mentioned above (+12 V, +18/ 24 V, +3V3 and +24
V). Connect the STBY pin (pin 10 of X200) to logical “L”
(low), i.e. to GND.
2. Over an input voltage range of 90 V
AC
to 276 V
AC
only the
+3V3 STBY output shall be up.
Normal Mode:
1. Apply a 12 ohm load resistor of sufficient power rating to all
outputs mentioned above (+12 V, +18/ 24 V, +3V3 and +24
V). Connect the STBY pin (pin 10 of X200) to logical “H”
(high), i.e. to the +3V3 STBY output via a 2,2 k pull up
resistor.
2. Over an input voltage range of 90 V
AC
to 276 V
AC
all
outputs shall be up. The voltage on the +3V3 STBY output
shall be 3.3 V over the entire input voltage range. The
voltage on the big 400 V capacitor on the power supply
should also be 400 V ± 10%.
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