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2.4
Notes
2.4.1
General
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•
Measure the voltages and waveforms with regard to the
chassis (= tuner) ground (H), or hot ground (I), 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 "Service Modes, ....") with a colour 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).
•
Where necessary, measure the waveforms and voltages
with (D) and without (E) aerial signal. Measure the
voltages in the power supply section both in normal
operation (G) and in standby (F). These values are
indicated by means of the appropriate symbols.
•
The picture tube panel has printed spark gaps. Each spark
gap is connected between an electrode of the picture tube
and the Aquadag coating.
•
The semiconductors indicated in the circuit diagram and in
the parts lists, are interchangeable per position with the
semiconductors in the unit, irrespective of the type
indication on these semiconductors.
•
Manufactured under license from Dolby Laboratories.
"Dolby", "Pro Logic" and the "double-D symbol", are
trademarks of Dolby Laboratories.
2.4.2
Schematic Notes
•
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).
•
Resistor values with no multiplier may be indicated with
either an "E" or an "R" (e.g. 220E or 220R indicates 220
ohm).
•
All capacitor values are expressed in micro-farads (µ= x
10^-6), nano-farads (n= x 10^-9), or pico-farads (p= x 10^-
12).
•
Capacitor values may also use the value multiplier as the
decimal point indication (e.g. 2p2 indicates 2.2 pF).
•
An "asterisk" (*) indicates component usage varies. Refer
to the diversity tables for the correct values.
•
The correct component values are listed in the Electrical
Replacement Parts List. Therefore, always check this list
when there is any doubt.
2.4.3
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.
Safety Instructions, Warnings, and Notes
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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
URL: www.atyourservice.ce.philips.com (needs subscription,
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.
2.4.4
Lead Free Solder
Philips CE is going to produce lead-free sets (PBF) from
1.1.2005 onwards.
Figure 2-2 Lead-free logo
This sign normally has a diameter of 6 mm, but if there is less
space on a board also 3 mm is possible.
Regardless of this logo (is not always present), one must treat
all sets from this date onwards according to the next rules.
Due to lead-free technology some rules have to be respected
by the workshop during a repair:
•
Use only lead-free soldering tin Philips SAC305 with order
code 0622 149 00106. If lead-free solder paste is required,
please contact the manufacturer of your soldering
equipment. In general, use of solder paste within
workshops should be avoided because paste is not easy to
store and to handle.
•
Use only adequate solder tools applicable for lead-free
soldering tin. The solder tool must be able
–
To reach at least a solder-tip temperature of 400°C.
–
To stabilise the adjusted temperature at the solder-tip.
–
To exchange solder-tips for different applications.
•
Adjust your solder tool so that a temperature around 360°C
- 380°C is reached and stabilised at the solder joint.
Heating time of the solder-joint should not exceed ~ 4 sec.
Avoid temperatures above 400°C, otherwise wear-out of
tips will rise drastically and flux-fluid will be destroyed. To
avoid wear-out of tips, switch "off" unused equipment or
reduce heat.
•
Mix of lead-free soldering tin/parts with leaded soldering
tin/parts is possible but PHILIPS recommends strongly to
avoid mixed regimes. If not to avoid, clean carefully the
solder-joint from old tin and re-solder with new tin.
2.
EN 5
P
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