Philips EM6E Service Manual page 35

5.8.2
Start-up Sequence
8V
17/39
I 2 C BUS
1
5V CON
RESET 8V CON
106 105
OTC
99 104
POR
STANDBY
low 7131/41 closed
high 7131/41 open
3
POR
7445
Figure 5-4 Start-up circuitry
The start up sequence differs from other sets (e.g. MG-sets or
EM2E-sets, but is same as in EM3E-set):
1.
When the set is switched "on", the 5 and 8 V lines
("+5V_CON" and "+8V_CON") of the standby power supply
are activated.
2. After the OTC senses them, the µP will address the HOP
2
via the I C-bus, to start the drive [1].
3. Via the "SUP-ENABLE" signal, the Main Supply is switched
"on" and will deliver the V_BAT to the Line deflection stage
[2].
4. EHT generation is now started.
5. The OTC will un-blank the picture.
6. When you switch "off" the set, this is done in a controlled
way via the POR signal [3].
Note: Standby is not directly achieved via the Standby line of
the microprocessor, but indirectly via the HOP circuitry.
5.8.3
ComPair
This chassis does not have an IR transmitting LED (as in MG-
sets). Therefore, a "Service" (ComPair) connector is
implemented at the rear side of the set, which is directly
accessible (as in A10-, EM2E-, EM3E and EM5E-sets). In
addition to this, there is also a blinking LED procedure to show
the contents of the error buffer.
When you use ComPair, you have the possibility to activate a
"stepwise start-up" mode. With this mode, you can initiate the
start-up sequence step by step. This also means that in certain
steps, some protections are not activated. This is sometimes
very convenient during repair.
5.8.4
Protections
Activating SDM via the "service pads" will overrule the
processor-controlled protections, but not the hardware
protections. This means, that the A/D-input protections (5 and
2
8 V) and the I C "not-acknowledging" info of the feature box
(FBX) and of the Tuner are overruled.
Caution: When doing this, the service technician must know
what he is doing, as it could lead to damaging the set.
The "ARC"- and/or "BRIDGECOIL" protection are hardly ever
triggered, however:
Service Modes, Error Codes, and Fault Finding
COLD HOT
EHT-INFO
5
START/STOP
OUT
HOP
29 START/STOP
CUTOFF
(from
CRT panel)
7141
5V
220 VAC
STBY
8V
SUPPLY
7131
MAIN
SUPPLY
SUP-ENABLE
Vbat
LINE DEFL.
+11D
(BRIDGECOIL
-PROT)
(ARC-PROT)
PROT-
SENSING
FRAME
DEFL
(NON-VFB)
CL16532044_023.eps
When you suspect the "ARC" protection, look for bad solder
joints and smell. By interrupting resistor 3497, this protection is
disabled (special attention needed!).
When you suspect the "BRIDGECOIL" protection, which can
also be due to a too wide picture amplitude, shorten G and S of
the E/W MOSFET 7480. This will disable the protection. You
will now have minimal horizontal amplitude. Re-align the
horizontal amplitude in the SAM menu and remove the G/S
short of TS7480.
5.8.5
Main Supply
2
The simplest way is, to replace the components of the Main
Supply with repair kit 3122 785 90550.
More detailed way:
1. Replace FET 7504 and zener 6505.
2. Disconnect the SSP panel.
3. Short B and E of TS7529, in order to put the Main Supply
in "on"-mode (TS7529 is blocking then).
Caution: To prevent that R3403 and TS7443 will be
damaged, first disable the HW-protection of the
deflection circuit. Therefore short circuit C2642 on the
LSP (diagram A4).
4. Attach a load of 500 Ω to V_BAT capacitor C2515 (the
140501
supply can not work without a minimum load).
5. Use a variac, and slowly increase the V_MAINS. Measure
over sensing resistors R3514//15, if a nice sawtooth
voltage becomes available.
6. Also measure the V_BAT. This may never exceed +141 V.
If it does, there is something wrong in the feedback circuitry
(e.g. regulator 7506).
Note: Be careful when measuring on the gate of FET TS7504.
This circuitry is very high ohmic and can easily be damaged
(first connect ground to measuring equipment, than measure
the gate).
5.8.6
Standby Supply
The simplest way is to replace the components of the Standby
Supply with repair kit 3122 785 90530.
5.8.7
Line Deflection
The simplest way is to replace the components of the Line
Deflection circuitry with repair kit: 3122 785 90330
Caution: item 3400 used in this chassis is different from the
part supplied in the kit. See partlist for correct value and
ordercode.
5.8.8
Frame Deflection
Caution: When the Frame Deflection circuitry is suspected,
one must be careful. Because there is a DC-voltage on the
frame deflection, the beam current could damage the CRT
neck, leading to a defective CRT.
To prevent this from happening, you must:
Interrupt the resistors 3403 and 3404 on the CRT panel
(diagram F1), in order to remove the "filament" voltage from the
tube (no beam current, so no chance of destroying the CRT).
Interrupt resistor 3403 on the LSP (diagram A4) to disable the
"SUP-ENABLE" line.
Measure with a multi-meter, or better with an oscilloscope, the
functionality of the Frame stage.
After you have found the cause, exchange the defective
component (e.g. TDA8177), and re-solder the interrupted
resistors.
EM6E AB 5. EN 37