Repair Tips - Philips EM5E AA Service Manual

diagram A6) will put the IC7700 in Standby mode (via tri-
state input pin 6). For more details, see chapter 9.
5.8

Repair tips

5.8.1 Miscellaneous
The relay you hear when you switch the set 'on' (from Standby
or via the mains switch), is from the degaussing circuitry. It is
not used for switching the Power Supply (as done in the MG-
chassis).
Take care not to touch the 'hot' heatsink while disconnecting
the SSB, despite the fact that the mains cord is out of the mains
socket. There can still be an annoying rest-voltage on the
heatsink for a short while. This, because the discharge
resistors 3502 and 3503 (on the LSP between hot and cold
part) are not stuffed for Europe. Instead, discharge resistors
3066 and 3057 on the Mains Switch panel are used, but
because they are located before the Mains switch, they only
discharge when this switch is 'on'.
Advice: when you remove the SSB, disconnect the Mains
cord, but keep the Mains Switch 'on'.
Do not try to measure on the SSB side, which is facing the 'hot'
heatsink. This is dangerous. Most service test points are
guided to the 'tuner' side and are indicated by the 'service'
printing. Where the circuitry was too 'crowded' for this printing,
you can find the correct location on the 'test point overviews' in
this manual (chapter 6).
A very large part of the LSP is 'hot', such as:
– The primary part of the Standby Supply.
– The whole Main supply (except for the secondary Audio
supply).
– And the complete deflection circuitry (so notice that the
deflection coil is hot!!).
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 5-3 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].
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
3. Via the 'SUP-ENABLE' signal, the Main Supply is switched
'on' and will deliver the V
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- and EM3E-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 (see also paragraph 5.4.3).
5.8.4 Protections
There are 'service pads' implemented on the SSB (items 9005
and 9006, outside the shielding), to force the set in SAM or
SDM (see also figure: 'SSB removal (part 3)' in Chapter 4). This
will overrule the processor-controlled protections, but not the
hardware protections. This means, that the A/D-input
protections (5 and 8 V) and the I
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:
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.
2
5.8.5 Main Supply
The simplest way is, to replace the components of the Main
Supply with repair kit (3122 785 90310)
More detailed way:
1. Replace FET 7504 and zener 6505.
2. Remove the SSB 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
140501
can not work without a minimum load).
5. Use a variac, and slowly increase the VMAINS. Measure
over sensing resistors R3514//15 if a nice sawtooth voltage
becomes available.
6. Also measure the V
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
EM5E 5.
to the Line deflection stage [2].
BAT
2
C 'not-acknowledging' info of
capacitor C2515 (the supply
BAT
. This may never exceed +141 V. If
BAT
EN 33