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GB 24
5.
•
Notice that a very big part of the set (Large Signal Panel)
is 'hot', meaning the primary part of the Standby supply,
the whole Main supply (except for the secondary Audio
supply) and the complete deflection circuit. So notice
that the deflection-coil is hot!
•
This set does not have an IR transmitting-LED. In its
place, a Service (ComPair) connector is implemented at
the rear of the set, which is directly accessible. In addition
to this, there is a blinking LED procedure to show the
contents of the error buffer.
•
The relay you hear during switching 'ON' (via the main
switch) is from the degaussing-circuitry. So it is not used
for switching the supply as in the MG-chassis.
•
When there is a menu in the picture, entry of service-
modes cannot be performed. So see to it that there is no
menu on the picture.
5.8.2
Repair tips
'Repair-tips how to repair the Main power supply:
•
Simplest way is to replace components of the Main
supply with repair kit (3122 785 90260)
•
More detailed way:
–
Replace FET 7504 and zener 6505
–
Remove SSB-panel
–
Short-circuit BE of TS7529 in order to put supply in
'on'-mode (TS7529 is blocking then)
–
Load capacitor C2515 (VBAT) with a load of 500
ohm. Supply can not work without a minimum load.
–
Use a variac to slowly increase the VMAINS.
Measure over sensing-resistors R3514/15 whether a
nice sawtooth-voltage becomes available. Also
measure the VBAT-output
–
VBAT may never exceed 141 V. If so there is
something wrong in the feedback-circuitry (e.g.
regulator 7506)
Repair-tips how to repair the Standby power supply:
•
Simplest way is to replace components of the Standby
supply with repair kit (3122 785 90270)
Repair-tips how to repair the Deflection-circuitry:
•
Simplest way is to replace components of the Deflection-
circuitry with repair kit (3122 785 90120)
Service-tips:
•
Be careful measuring on gate of FET 7504. Circuitry is
very high ohmic and can easily be damaged.
•
Take care not to touch 'hot' heatsink while disconnecting
SSB, despite the fact that mains cord is out of mains
socket. There still is an annoying rest-voltage for a short
while.
•
Do not try to measure on side of SSB directed to the hot
heatsink. This is dangerous. All service test points are
guided to the Tuner side and are pointed out by service
printing. Where the circuitry was too crowded to place
this service-printing it has been explained on the Test
point overviews in this manual
EM1A
Fault finding and repair tips
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