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Posted by JANA on 11/05/07 03:17
What your are seeing is most likely the assembly glue. During the assembly
run, some of the components have to be glued down in to place so that they
do not displace when the board passes through the soldering bath.
Most of the time, bad capacitors are not visibly bad. Leaky capacitor, means
that the cap is becoming resistive internally. This would be in effect,
"resistance leakage". To properly test caps, you need an ESR meter to start
with. A capacitor meter is also good to know if the uF value is correct.
There are many more types of failures that can occur to make a power supply
fail than just capacitors. Without the proper training, service information
(service manual), and test equipment, the power supply will probably not be
possible to repair unless you would know the exact parts to change.
--
JANA
_____
"Joe" <none@given.now> wrote in message
news:none-0411071904330001@dialup-4.232.123.160.dial1.losangeles1.level3.net...
I have a Philips DVD Player, model DVP 642.
It will be two years old next month.
It seems to have a power supply problem that is similar to what others
have reported, and is likely due to a bad electrolytic capacitor.
The symptom is:
The unit is in standby mode, with a red LED lit, as it is supposed to be.
Pressing the power-on button causes the red LED to turn off - as it is
supposed to - but nothing else happens. After a few seconds, the red LED
comes back on as though the power-on button had never been pressed.
Pressing and holding for a few seconds the power-on button makes the unit
seem to come to life and operate normally. No need to hold down the
power-on button.
The unit seems to function normally until it is shut off (into standby
mode), and the the same symptoms happen when I try to power it up again.
So far I have opened up the unit and removed the power supply.
No capacitors look to be bulging.
There is some rubbery pale-yellow stuff that seems to have been spread
deliberately on the circuit board, near one of the capacitors, but
especially along where a 7 conductor ribbon cable enters the circuit
board.
Is this the leaky stuff that some have called "yellow gunk" from a split
open capacitor? I picked at the stuff, and it is definitely *rubbery* and
not all all liquid.
Or is this some stuff that is meant to be a strain relief from the ribbon
cable to the PC board?
Does anyone know where to obtain a schematic at least for the power
supply? It would help to at least identify the caps on this board. Any
constructive suggestions?
A related question: If I parallel a pair of capacitors to get close to
the needed value, do the bodies of the two caps have to be insulated or
separated from each other?
--- Joe
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