Prev: Panasonic 27XF25CW 27" TV Horizontal Line until warms up
Next: Maplin/Trust 500 UPS
From: mm on 15 Mar 2010 01:21
On Mon, 15 Mar 2010 01:19:31 -0400, mm <NOPSAMmm2005(a)bigfoot.com>
wrote:

>having symptoms of a well-known problem with a
>>certain capacitor in the power supply.

So I forgot to ask, what is the well-known problem, and can you tell
by looking which capacitor in the power supply?

If you didn't figure it out by looking, how did you find it?

I can't always do much, but I can replace a power supply cap.
>
>Well, I'm not happy to hear this because I have their DVDR 6765 (or
>some 4 digit number beginning with 6) the latest one they've sold and
>it's nearing two years of age.

From: Joe on 15 Mar 2010 05:14
In article <2sgrp5hb1tg4eohk37o64qclpn48nqs34v(a)4ax.com>, mm
<NOPSAMmm2005(a)bigfoot.com> wrote:

> On Mon, 15 Mar 2010 01:19:31 -0400, mm <NOPSAMmm2005(a)bigfoot.com>
> wrote:
>
> >having symptoms of a well-known problem with a
> >>certain capacitor in the power supply.
>
> So I forgot to ask, what is the well-known problem, and can you tell
> by looking which capacitor in the power supply?
>
> If you didn't figure it out by looking, how did you find it?
>
> I can't always do much, but I can replace a power supply cap.
> >
> >Well, I'm not happy to hear this because I have their DVDR 6765 (or
> >some 4 digit number beginning with 6) the latest one they've sold and
> >it's nearing two years of age.

The well-known problem was with the DVP 642. I found the info on the web site

http://tech.groups.yahoo.com/group/philips_dvp642/

An article there gave the actual part number which is printed on the
circuit board for that particular capacitor.

The URL, above, also has info on other Philips DVD players. Have a look.

--- Joe
From: Arfa Daily on 15 Mar 2010 05:20

"Phil Allison" <phil_a(a)tpg.com.au> wrote in message
news:805kfmFpesU1(a)mid.individual.net...
>
> "Arfa Daily"
>>
>> Further circuitry damage can often be a consequence of failing smps
>> secondary-side electrolytics. If the supply monitors say the 12v rail for
>> regulation feedback, and the filter cap on that rail goes bad, the
>> resulting hash and ripple can appear to the sensing circuit as a low
>> output. This causes the m/s ratio of the chopper drive to open up in an
>> effort to restore the rail to the correct value. As all the other rails
>> are tightly magnetically coupled to the bad rail as a consequence of them
>> all sharing the same transformer core, the end result is that the 3.3v
>> and 5v rails can go sky-high, causing a trail of catastrophic damage to
>> various LSIs in the equipment.
>
>
> ** Over-voltage protection is essential for devices with such SMPSs - a
> sacrificial zener bridging the regulated voltage will do the job for a
> single output supply.
>
> Multiple output supplies need something a bit more complex that monitors a
> sum off all the DC outputs and reacts to any significant increase.
>
> Many cheap and some expensive products do not have anything.
>
>
>
> ..... Phil
>
>

Yes, agreed. Most LCD TV switchers have sophisticated shutdown circuitry for
the main control IC, and sometimes for the pfc supply as well. These
circuits measure under and over voltage, as well as over-current conditions,
and can represent a fault-finding nightmare, as you try to over-ride them
with the supply in isolation from the TV, to see which supply or protection
circuit, is causing the shutdown ...

But as you say, most cheapo switchers as found in DVD players and home
cinemas and the like, have absolutely nothing south of the rectifier.

Arfa


From: Arfa Daily on 15 Mar 2010 05:35

"mm" <NOPSAMmm2005(a)bigfoot.com> wrote in message
news:2sgrp5hb1tg4eohk37o64qclpn48nqs34v(a)4ax.com...
> On Mon, 15 Mar 2010 01:19:31 -0400, mm <NOPSAMmm2005(a)bigfoot.com>
> wrote:
>
>>having symptoms of a well-known problem with a
>>>certain capacitor in the power supply.
>
> So I forgot to ask, what is the well-known problem, and can you tell
> by looking which capacitor in the power supply?
>
> If you didn't figure it out by looking, how did you find it?
>
> I can't always do much, but I can replace a power supply cap.
>>
>>Well, I'm not happy to hear this because I have their DVDR 6765 (or
>>some 4 digit number beginning with 6) the latest one they've sold and
>>it's nearing two years of age.
>

I don't know specifically with your model, but the most common problems
caused by bad electrolytics in items like this are no or intermittent
operation, a failure to come out of standby, a failure of the standby supply
to come up if the unit has been fully off-power, pattern on the screen of
the display, or random error messages on the screen like "no signal being
received" or some such.

If there is no physical evidence of a bad cap, such as bulging, leaking, or
a popped bung, then the best (and only, in my opinion) way of locating bad
or 'on their way' caps, is with an ESR meter. One of these will locate 99%
of bad caps without even having to remove them from the board, and is worth
its weight in gold to a commercial repairer. In saying that, measuring ESR
is a bit of a black art in terms of interpreting the readings the meter
gives you, but the digital types like Bob Parker's (now remodeled to the
"Blue ESR Meter" - see Anatek Corporation's website) make this
interpretation a whole bunch easier. Secondary-side caps are the most common
for giving a physically visible clue, and the worst offenders are those
mounted close to a heatsink. Primary-side troublemakers are usually
physically small low-value types - up to about 47uF - and are almost always
mounted close to a heatsink. Dead supply with no blown fuses, is the typical
symptom from these.

The best thing that you can do to prolongue the life of any power supplies
in DVD players or HC units, is to make sure that they are not locked up in a
cabinet with poor airflow, and that they are on the bottom of any equipment
stack, so that they are not drawing warm air from some unit underneath.

Arfa


From: Jim Yanik on 15 Mar 2010 08:19
"Arfa Daily" <arfa.daily(a)ntlworld.com> wrote in
news:sKgnn.362533$yV6.112805(a)newsfe27.ams2:

>
> "William R. Walsh"
> <newsgroups1(a)idontwantjunqueemail.walshcomptech.com> wrote in message
> news:j-WdnVY6usNsGQDWnZ2dnUVZ_uOdnZ2d(a)mchsi.com...
>> Hi!
>>
>>> I bought a Philips DVP 642 DVD player in December 2005, and 2 months
>>> shy of 2 years, it failed
>>
>> This sort of thing is completely inexcusable. I suppose it's brought
>> on by cost, or at least I hope so, given how many years have gone by
>> since the electrolytic plague took place. This computer (see the sig)
>> is running on all of its original electrolytics, as is the Deskpro EN
>> a few places down and many other devices. The EN runs some of its
>> 'lytics a little bit warm to
>> the touch, but it's still going. It runs 24/7.
>>
>> This machine also spends a large amount of time powered on, and was
>> used as
>> a server prior to falling into my possession sometime in 2002.
>>
>> I tried to save a 16-port SMC ethernet switch after it started acting
>> up. One of the electrolytics was blown up, but a replacement did not
>> restore normal operation. My guess is that damage to the other
>> circuitry had taken place.
>>
>> So it *can* be done. I suppose the only reason it doesn't always work
>> out is
>> due to cost and the odd defective unit.
>>
>
>> William
>>
>
> Further circuitry damage can often be a consequence of failing smps
> secondary-side electrolytics. If the supply monitors say the 12v rail
> for regulation feedback, and the filter cap on that rail goes bad, the
> resulting hash and ripple can appear to the sensing circuit as a low
> output. This causes the m/s ratio of the chopper drive to open up in
> an effort to restore the rail to the correct value. As all the other
> rails are tightly magnetically coupled to the bad rail as a
> consequence of them all sharing the same transformer core, the end
> result is that the 3.3v and 5v rails can go sky-high, causing a trail
> of catastrophic damage to various LSIs in the equipment.
>
> Arfa
>
>
>

The SMPS in TEK 1710/20/30 series TV products would have the cap on the +5V
rail rise in ESR,the supply would drive ALL the other supply rails high,
the +40V would climb to >60v,the HV oscillator xstr would
overdissipate,char the PCB to the point it became conductive,and the supply
would go into "burst" mode. I had to grind out the charred area,fill with
epoxy,and set new eyelets and do track repairs.I also put in a better rated
+5v filter cap,no more problems.

Other techs just replaced the whole PCB.
I was always replacing bad electrolytics on the 1700 monitors.
They typically were installed in racks that kept their temp above "normal".

--
Jim Yanik
jyanik
at
localnet
dot com
First  |  Prev  |  Next  |  Last
Pages: 1 2 3 4 5
Prev: Panasonic 27XF25CW 27" TV Horizontal Line until warms up
Next: Maplin/Trust 500 UPS