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TPF1.4A LA
2. Safety Instructions, Warnings and Notes
index of this chapter:
2.1 Safety Instructions
2.2 Warnings
2.3 Notes
2.1 Safety Instructions
Safety regulations require that during a repair:
·
Connect the set to the AC Power via an isolation
transformer (> 800 VA).
·
Replace safety components, indicated by the symbol
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.
Safety regulations require that after a repair, the set must be
returned in its original condition. Pay in particular attention to
the following points:
·
Route the wire trees correctly and fix them with the
mounted cable clamps.
·
Check the insulation of the AC Power lead for external
damage.
·
Check the strain relief of the AC Power cord for proper
function.
·
Check the electrical DC resistance between the AC Power
plug and the secondary side (only for sets which have a AC
·
Power isolated power supply):
1. Unplug the AC Power cord and connect a wire
between the two pins of the AC Power plug.
2. Set the AC Power switch to the "on" position (keep the
AC Power cord unplugged!).
3. Measure the resistance value between the pins of the
AC Power plug and the metal shielding of the tuner or
the aerial connection on the set. The reading should be
between 4.5 Mohm and 12 Mohm.
4. Switch "off" the set, and remove the wire between the
two pins of the AC Power plug.
·
Check the cabinet for defects, to avoid touching of any
inner parts by the customer.
2.2 Warnings
·
All ICs and many other semiconductors are susceptible to
electrostatic discharges (ESD ). Careless handling
during repair can reduce life drastically. Make sure that,
during repair, you are connected with the same potential as
the mass of the set by a wristband with resistance. Keep
components and tools also at this same potential.
·
Be careful during measurements in the high voltage
section.
·
Never replace modules or other components while the unit
is switched "on".
·
When you align the set, use plastic rather than metal tools.
This will prevent any short circuits and the danger of a
circuit becoming unstable.
2.3 Notes
2.3.1 General
1. Measure the voltages and waveforms with regard to the
chassis (= tuner) ground ( ), or hot ground ( ), depending
on the tested area of circuitry. The voltages and waveforms
shown in the diagrams are indicative. Measure them in the
Service Default Mode (see chapter 5) with a color bar
signal and stereo sound (L: 3 kHz, R: 1 kHz unless stated
otherwise) and picture carrier at 475.25 MHz for PAL, or
61.25 MHz for NTSC (channel 3).
2. Where necessary, measure the waveforms and voltages
with ( ) and without ( ) aerial signal. Measure the
voltages in the power supply section both in normal
operation ( ) and in stand-by ( ). These values are
indicated by means of the appropriate symbols.
3. The semiconductors indicated in the circuit diagram and in
2. Safety Instructions, Warnings and Notes
the parts lists, are interchangeable per position with the
semiconductors in the unit, irrespective of the type
indication on these semiconductors.
4. Manufactured under license from Dolby Laboratories.
"Dolby" and the "double-D symbol", are trademarks of
Dolby Laboratories.
2.3.2 Schematic Notes
1. All resistor values are in ohms and the value multiplier is
,
often used to indicate the decimal point location (e.g. 2K2
indicates 2.2 kohm).
2. Resistor values with no multiplier may be indicated with
either an "E" or an "R" (e.g. 220E or 220R indicates 220
ohm).
3. All capacitor values are given in micro-farads (u= x10 ),
nano-farads (n= x10 ), or pico-farads (p= x10
4. Capacitor values may also use the value multiplier as the
decimal point indication (e.g. 2p2 indicates 2.2 pF).
5. An "asterisk" (*) indicates component usage varies. Refer
to the diversity tables for the correct values.
6. The correct component values are listed in the Electrical
Replacement Parts List. Therefore, always check this list
when there is any doubt.
2.3.3 Rework on BGA (Ball Grid Array) Ics
General
Although (LF)BGA assembly yields are very high, there may still be
a requirement for component rework. By rework, we mean the
process of removing the component from the PWB and replacing it
with a new component. If an (LF)BGA is removed from a PWB, the
solder balls of the component are deformed drastically so the
removed (LF)BGA has to be discarded.
Device Removal
As is the case with any component that, it is essential when
removing an (LF)BGA, the board, tracks, solder lands, or
surrounding components are not damaged. To remove an(LF)BGA,
the board must be uniformly heated to a temperature close to the
reflow soldering temperature. A uniform temperature reduces the
chance of warping the PWB.To do this, we recommend that the
board is heated until it is certain that all the joints are molten.
Then carefully pull the component off the board with a vacuum
nozzle. For the appropriate temperature profiles, see the IC data
sheet.
Area Preparation
When the component has been removed, the vacant IC area must
be cleaned before replacing the (LF)BGA.Removing an IC often
leaves varying amounts of solder on the mounting lands. This
excessive solder can be removed with either a solder sucker or
solder wick. The remaining flux can be removed with a brush and
cleaning agent.After the board is properly cleaned and inspected,
apply flux on the solder lands and on the connection balls of
the (LF)BGA.
Note: Do not apply solder paste, as this has shown to result in
problems during re-soldering.
Device Replacement
The last step in the repair process is to solder the new component
on the board. Ideally, the (LF)BGA should be aligned under a
microscope or magnifying glass. If this is not possible, try to align
the (LF)BGA with any board markers. To reflow the solder, apply a
temperature profile according to the IC data sheet. So as not to
damage neighbouring components, it may be necessary to reduce
some temperatures and times.
More Information
For more information on how to handle BGA devices, visit this
www.atyourservice.ce.philips.com
URL:
not available for all regions). After login, "select Magazine", then
go to "Workshop Information". Here you will find Information on
how to deal with BGA-ICs.
-9
-12
).
(needs subscription,
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