Job Number |
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0304-77 |
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Equipment type |
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TV (17”) |
Made in: |
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Maker/Model/Chassis |
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PHILIPS |
42KT3150 |
KT3 chassis |
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Dates 2003 |
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In |
Repaired |
Out |
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Wed.02.Apr |
Mon.07.Apr |
Sat.12.Apr |
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Comments |
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TV was bought 2nd
hand for 20Euros. It was severely repaired, as if it was in a
repair-education school for novice students. |
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1 |
Turns off (dead) immediately
after switch on |
Full repair description and observations |
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1 |
Very strangely, when the TV set
was opened, and the chassis was turned from vertical position to horizontal
position (for servicing and diagnosis) the TV worked perfectly (raster
present) |
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2 |
However a very abnormal
whisling noise was produced from somewhere in the circuit, presumingly the
High voltage transformer. On better checking, to my astonishment, there was
sparks from the EHT transformer High tension wire (carrying the 20kV). The TV
was switched off and the High Voltage (on the CRT plates) was discharged
carfully to earth |
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3 |
The EHT wire was burnt and in
consequence slightly perforated. At first I taught that a previous stupid
technician by mistake touched the wire with the soldering iron and hence
melting/burning the plastic insulation of the wire. On more evalation, I
noted that there was plastic meltings/burns on a
high wattage resistor, in close vicinity to the wire. What happened is that
the EHT wire touched this resistor. On operation the resistor became very hot
and as a result it melted slowly the wire insulation until it became
perforated. Probably a spark passed into circuit causing it to switch off. |
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4 |
The perforation was properly
insulated using evostick glue, then few rounds of electric tape, and a
pull-to-tight plastic band (I don’t what it is exactly called) to keep
everything in place - with time and
heat the tape glue can wear off and the tape may fall. |
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5 |
I put the chassis back in the
original upright position and switched on. The TV switched but there was no
focus!!! Turned off again, and noticed that focus wire came free of from
trippler. Resoldered it again, turned on and TV was OK. No whistling sound
was produced from the EHT wire. |
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6 |
I noticed that the picture was
a bit dark (even on full brightness controls). There was no G2 adjustment and
R,G,B presets on CRT plate where already set to
maximum! However there was a preset (R422) which increased the contrast and
this helped to make the picture brighter and, on the whole, better. |
Repair summary |
INSULATION OF EHT CABLE PERFORTAED |
Precautions, fouls and advises |
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1 |
I managed to get a nice eht shock. The sound was more
scary than the pain itself. When working with EHT, always discharge
EHT capacitor (tube) by a high Ohm resistor for sake of safety |
1 |
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