The 22 Month Eletrolytics

[mm]

On Mon, 15 Mar 2010 01:19:31 -0400, mm <NOPSAMmm2005@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.

 

[Joe]

In article <2sgrp5hb1tg4eohk37o64qclpn48nqs34v@4ax.com>, mm
<NOPSAMmm2005@bigfoot.com> wrote:

On Mon, 15 Mar 2010 01:19:31 -0400, mm <NOPSAMmm2005@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

 

[Arfa Daily]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:805kfmFpesU1@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

 

[Arfa Daily]

"mm" <NOPSAMmm2005@bigfoot.com> wrote in message
news:2sgrp5hb1tg4eohk37o64qclpn48nqs34v@4ax.com...

On Mon, 15 Mar 2010 01:19:31 -0400, mm <NOPSAMmm2005@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

 

[Jim Yanik]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in
news:sKgnn.362533$yV6.112805@newsfe27.ams2:

"William R. Walsh"
newsgroups1@idontwantjunqueemail.walshcomptech.com> wrote in message
news:j-WdnVY6usNsGQDWnZ2dnUVZ_uOdnZ2d@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

 

On Mon, 15 Mar 2010 15:34:37 +1100, "Phil Allison"
<phil_a@tpg.com.au>wrote:

Mr. Liebermann last seen crashing in flames over enemy lines

Sorry It's you who crashed, several years ago in fact.

.....heh

 

[b]

On Mar 15, 3:14 am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

"William R. Walsh" <newsgrou...@idontwantjunqueemail.walshcomptech.com
wrote in messagenews:j-WdnVY6usNsGQDWnZ2dnUVZ_uOdnZ2d@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

I've seen this with quite dramatic consequences. 2 years ago a friend
brought me a budget DTT-DVD player which was dead. Opened up,and
several caps had literally exploded, but only one was in the psu. the
others were downstream, on the main/processor pcb. Clearly there had
been some catastrophic voltage rise.

The other week I picked up a DTT set top box. Same thing - lots of
exploded caps, with only the legs still on the pcb. The few remaining
electolytics on the main pcb were bulging.
Needless to say, both these units were promptly scrapped as BER.
The lesson is: when something is acting erratically, don't wait before
changing the caps!
-B

 

[William R. Walsh]

Hi!

Further circuitry damage can often be a consequence of failing smps
secondary-side electrolytics.

Every cap in the switch's SMPS was fine, and the outputs were right on. A
large (filter?) cap on the main board blew its top. It looked like it had
been working up to this for a while. It had been working great up until the
moment it fell off the wagon.

A replacement cap didn't help much, and I sure couldn't complain about six
years of service from a used switch that I paid all of $10 for. I saved the
SMPS for later use and recycled the rest. A new D-Link switch replaced it.
What struck me was how the components have shrunk. The SMC switch had
several large ICs, two of them responsible for switching and one that
appeared to be a sort of processor (for what I have no idea, it was not a
managed switch). There were some artifacts near the processor for RAM and
ROM, probably used to add management functionality?

The D-Link switch is based on a Realtek platform. It runs cooler, performs
just as well and is a simpler design.

William

 

[[SMF]]

This looks like a good thread to jump into:

I have a friend that has a Hafler TA-1600. The bass is non-
existent and every thing else is a bit flat/muted. Each
channel has a separate board powered by a common, multi-tap,
dual voltage transformer that outputs ~32 and ~64 VAC with
120 VAC as the primary.

The transformer has two input leads and 12 output leads. One
group of three per board per voltage.

Each board has two power inputs, comprising the above voltages,
that contain three leads each that are Red - Black - Red. Red
to red gives the 32/64 volt for each input, while any red to
black combination gives half of the red to red voltage in that
winding group.

There is not any visible damage to any component.
Each board sounds identical to the other when isolated.
This amp is currently disassembled so that I may work
on each board individually, yet I'm not sure whether
attempting to save the system is actually worth the bother.

With reading all of the electrolytic problems that seem to
be permeating the electronic field, I am seeking information
to a possible fix, and hope that maybe someone here might
actually have some experience with the Hafler TA's and
could point to some resources/give some hints or how to's
with this unit.

Thanks,

Steve

PS: the voltages listed above are measured voltages. The
transformer does not have any specs listed on it.

 

[William Sommerwerck]

If the sound is identically bad on both channels, that suggests something
common to both channels, such as the power supply. The possibility that a
coupling cap has suddenly lost value is unlikely, as the same cap would have
to fail on both channels.

I would also look at the /system/ in which the amplifier is installed. The
lack of bass might be due to an interface problem elsewhere.