Circuit Descriptions
EN 56
Q552.2L LA
7.
2012-Mar-16
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div. table
Figure 7-4 Test instructions
Following checks have to be performed:
•
check fuse (F101)
•
standby check V
STB
(C306), measure 3.3 V
•
PFC voltage check (C644), measure 380 - 400 V; if no PFC
applied, measure 311 @ 220 V
•
multi-level check V
SSB
(C208), measure 12.3 V
•
multi-level check V
SND
(C233), measure 24.5 V
•
reference voltage check (U401), measure 12 V (appr.).
SAFETY INSTRUCTION
Replace safety components, indicated by the symbol
h
, only
by components identical to the original ones. Any other
component substitution (other than original type) may increase
risk of fire or electrical shock hazard.
7.3
DC/DC Converters
The on-board DC/DC converters deliver the following voltages
(depending on set execution):
•
+3V3-STANDBY, permanent voltage for the Stand-by
controller, LED/IR receiver and controls; connector 1M95
pin 1
•
+12V, input from the power supply for TV550 common
(active mode); connector 1M95 pins 6, 7 and 8
•
+24V, input from the power supply for DVB-S2 (in active
mode); connector 1M09 pins 1 and 2
•
+1V1, core voltage supply for PNX855xx; has to be started
up first and switched "off" last (diagram B03B)
•
+1V2, supply voltage for analogue blocks inside PNX855xx
•
+1V8, supply voltage for DDR2 (diagram B03B)
•
+2V5, supply voltage for analogue blocks inside PNX855xx
(see diagram B03E)
•
+3V3, general supply voltage (diagram B03E)
•
+5V, supply voltage for USB and CAM (diagram B03E)
•
+5V-TUN, supply voltage for tuner (diagram B03E)
•
+V-LNB, input voltage for LNB supply IC (item no. 7T50)
•
+5V-DVBS, input intermediate supply voltage for DVB-S2
(diagram B08A)
•
+3V3-DVBS, clean voltage for silicon tuner and DVB-S2
channel decoder
•
+2V5-DVBS, clean voltage for DVB-S2 channel decoder
•
+1V-DVBS, core voltage for DVB-S2 channel decoder.
A +12 V under-voltage detector (see diagram B03C) enables
the 12V to 3.3V and 12V to 5V DC/DC converters via the
ENABLE-3V3-5V line, and the 12V to 1.8V DC/DC converter
via the ENABLE-1V8 line. DETECT2 is the signal going to the
Stand-by microcontroller and ENABLE-3V3n is the signal
coming from the Stand-by microcontroller.
Diagram B03D contains the following linear stabilizers:
•
+2V5 stabilizer, built around item no. 7UCO
•
+5V-TUN stabilizer, built around items no. 7UA6 and 7UA7
•
+1V2 stabilizer, built around items no. 7UA3 and 7UA4.
Diagram B08A contains the DVB-S2-related DC/DC
converters and -stabilizers:
•
a +24V under-voltage detection circuitry is built around
item no. 7T04
•
the switching frequency of the 24 to 14...20V switched
mode converter is 350 kHz (item no. 7T03 and +V-LNB
lines)
•
the output signal on the +V-LNB line goes to the LNBH23Q
(item no. 7T50)
•
the LNBH23Q (item no. 7T50) sends a feedback signal via
the V0-CNTRL line
•
the switching frequency of the +5V-DVBS to +1-DVBS
switched mode converter is 900 kHz (item no. 7T00)
•
a delay line for the +2V5-DVBS and +1V-DVBS lines is
created with item no. 3T03 (R=10k) and 2T06 (C=100n)
•
a 3.3V to 2.5V linear stabilizer is built around item no. 7T01
•
a 5V to 3.3V linear stabilizer is built around item no. 7T02.
Diagram B08B contains the DVB-S2 LNB supply:
•
the +V-LNB signal comes from item no. 7T03
•
the V0-CTRL signal goes to item no. 7T03
•
the LNB-RF1 goes to the LNB.
Figures gives a graphical representation of the DC/DC
converters with its current consumptions:
19132_013_111221.eps
111222
Normal operation
Apply the mains voltage (AC
in
)
Pull the Standby pin to LOW (GND)
Pull the BL_ON_OFF pin to HIGH (3.3 V)
Check the main supply at C208: measure 12.3 V
Check the audio supply at C233: measure 24.5 V
Check the PFC voltage at C644
PFC present: measure 380 V to 400 V
PFC not present: measure ACin × 2
No turn on
Check
First step
Second step
Check the entire block (PC102, V
CC
, etc.)
Check the entire block (V
CC
, ICs, etc.)
Allow the power supply to start-up a few times
Check the Standby voltage
at C306: measure 3.3 V
Check the reference voltage of the
LED Driver (U401): measure approximately 12 V
Check the fuse (F101)
Check the entire block (V
CC
, ICs, etc.)
