Need help troubleshooting Series 2 TiVo

On Apr 2, 1:12*pm, "Peter H. Coffin" wrote:
On Wed, 2 Apr 2008 04:14:59 -0700 (PDT), wrote:

The other experimental results listed on the discussion page support
my conclusions well, by indicating higher measurement for human
resistance, and calling out problems with the main article text that
would exaggerate lethality with regard to fibrillation.


The values in the article are not more wrong then your numbers are and
I have no doubt you actually measured those values. Contact
resistance will frequently play a major role in shock hazards. In
your measurement, I'm betting you pinched the probes with your left
and right hand (probably reasonble hard based on the closeness of the
wet and dry values). Try making the measurements again, but this time
get 2 pieces metal and grab them with each hand allowing the probe to
touch the metal. The contact area of your skin is now much larger to
the conductor path and the measurement will be considerably less.

I got curious enough with the 'pure water is an insulator' possibility
that I did run an experiment myself. I took two chunks of copper, one
in each hand to measure my body resistance, it came to 88K. I put
about 1/4 oz of DI water on my hands (I work in an electronics lab);
repeated and I got 8.1K. So while we will both agree that DI water is
an excellent insulator, it can impact electrocution likelyhood. If I
had though if it, I should have cleaned both my hand and the copper
with alchohol. I will speculate that removal of comtaminants will
increase the resistive path, but I don't think it will get you even
half way back to the waterless event.

UL/CSA and the IEC use 2K as the human body resistance. There can
always be an argument weather this should be higher or lower, but it
is reasonable in my mind considering human safety is involved. If you
can imagine someone reaching out from a pool, with his chest against
the earth edging and grabbing with both hands an aluminum pool skimmer
that had the bad fortune to have become live, the path through the
heart will almost surely be below the 1K number.

I will further speculate that the use of a DVM is not a good way to
accurately measure human body resistance. Measuring the current
through you having a +12V applied would probably be more accurate.
While the likelyhood is still low at +12V, it is possible that you
can concoct a scenario where this would be lethal (the pool example
above).

On Apr 3, 1:14*am, w_tom wrote:
On Apr 2, 7:51 pm, (Scott Lurndal) wrote:

It's already been pointed out to you at least three times that the
TIVO power supply is fed from mains voltages (NA 120V, ROW 240V),
which can be quite hazardous.

* Do you read or just assume what I posted?

Yes, we have read what you posted. Have you ever seen the inside of a
Tivo? It uses an open frame power supply (at least mine does). If
the cover is off a tivo, there is high (well, 200 ish volts anyways)
right there.


* Using an ice pack to isolate failures on a motherboard is not
hazardous. *

I work in a lab where we work in mixed environment (high and low
voltage boards) all the time. Since I work with comptetnt people, I
would never expect to see such foolhardy behavior as allowing water to
be present while debugging one of these boards. If I did see it, I
would give a royal reaming to the inept person doing it.


* Common knowledge now posted a fourth time. *Same basic knowledge
that also makes obvious "no hazardous voltages exist on a
motherboard".

Yes, we agree with that. 12V and below is pretty safe. I still won't
work on it with wet hands.

There is anectdotal evidence that with the right conditions 12V can
be lethal.


* Amazing how many have posted fears without learning the basics.
Scott did not read disk drive datasheets to somehow know 140 degrees
must be destructive. *Scott did not have basic electronics knowledge
to know why water would not cause digital electronics harm - even to
digital electronics of 1960s vintge. *

* Scott demonstrateds why more than 50% of employees in the Silicon
Valley are now immigrants. *Too many somehow know - do not understand
how to first learn basic facts.

No, actually you have demostrated quite well the expertise of many
foreign workers. I assume you are asian on your english. Drive
temperatures come up periodically, and everyone (even our resident
troll) agrees cooler is better for the life of a hard drive and this
is particularly important in a DVR where it runs 24/7. Spend some
time researching projected HDD life at 30, 40 and 60C and let me know
what you find.

Can you cite a source that 50% of silicon valley is foreigners? We
have been losing american engineers here and having foreign nationals
cycle through the organization. They come on board with a very poor
background, spend about 18 months learning the ropes, then go back.
It's a shame the US government allows this to happen, but hey, that's
globalization. The Japanese can be OK, the tiawanese are not so good;
it will be 10+ years before the chinese can figure out how to design
anything.

On Apr 3, 7:17 am, wrote:
No, actually you have demostrated quite well the expertise of many
foreign workers. I assume you are asian on your english.

Ever take a technical writing course? English used in technical
writing is different from that taught to English majors who are taught
to personalize. In good technical prose, wording should be so
impersonal that emotional types might even take insult.

We also would not use ice packs on ICs. We use freeze spray - and
rarely. However, the engineer that innovates must use what is
available. An ice pack to cool selective parts on a Tivo does not
create human risk AND does not threaten electronic life expectancy.
Water on digital electronics does not harm anything. Water drops from
an ice pack are even less problematic. But a high paid tech must use
freeze spray so that time and money is not wasted drying the board.

Where is a recommendation of running a disk drive constantly at 60
degree C? Why write about what is not stated or relevant here? Why
confuse diagnostics with actual Tivo operation? Did you remember the
point of every post? OP needs diagnostic solutions. Please remember
the context; instead address the OP's problem.

Any disk drive will work just fine at 140 degree F. It may only
work for 9.6 years instead of 10 at that temperature. Irrelevant?
Did you forget the context? 1) Heat is a diagnostic tool. 2) Disk
driver is not part of the problem; need not be heated to identify a
failure.

OP must locate a hardware failure. Why are posts so irresponsible as
to discuss electrocution from 12 volts and total destruction of the
world because a disk drive is at 140 degrees? Irresponsible. Those
threats do not exist AND are completely irrelevant to solving the OP's
problem.

Diagnostics never recommended heating a drive to 140 degrees. That
was another post creating hypothetical myths only to create argument.
If that post was based in technical knowledge or in what was
previously posted, then no disk drive was being heated to 140 degrees.
But that poster had so little technical grasp as to think a drive at
140 degrees gets destroyed. Heating a disk drive to 140 degrees is
acceptable wherever the person is using a technical brain - not
throwing grenades into a discussion.

Disk drive is but another example of posters who don't understand
basic technology, do not bother to first read datasheets, did not
comprehend what was posted, and cannot even remember the topic. Disk
drive has nothing to do with the OP's problem - as this author stated
up front.

Why argue silliness? Every post about myths - disk drive destroyed
by 140 degrees, electrocution from a motherboard, fear of rare water
drops from an icepack - is not relevant to solving the OP's problem.
Amazing how many fears and myths were posted that do not even apply to
the OP's problem. Amazing how many posted while completely ignoring
previous posts:
Do not use a finger to find hot parts on a power
supply since that supply will have 300 volt charges

Why use that poor English that is not acceptable when writing
technical prose? Well, many don't understand a difference between how
to talk to a wife verses how to write impersonal and technical. I am
surprised that one using too many personalized sentences (poor
English) would be critical of good technical English.

A Silicon Valley joke: IC is not integrated circuits. Indian and
Chinese who, according the EE Times and other sources, now constitute
50% of the valley employees. One need only read the many silly posts
here about electrocution from 12 volts to appreciate why America needs
so many immigrants. Every post about Tivo motherboard electrocution
identifies a poster who is in total denial of basic electrical facts.
Nothing on that motherboard will electrocute anyone. Why so many posts
advocating myths? A serious problem in America also demonstrates why
so many also believed myths about Saddam's WMDs - when facts and
numbers said otherwise.

Appreciate why so many would also believe those WMD myths. How many
are so foolish as to argue that 12 volts can kill? Blunt, technical,
and now personally challenging the intellectual grasp of some here who
do nothing to help solve the OP's problem. So many posters who do not
even understand 'context'.

In article 19f7705c-4a32-48a5-bfef-fff8053db405
@m44g2000hsc.googlegroups.com, says...
|On Apr 2, 6:14 am, wrote:
| We can agree to disagree on what we each think is safe.
|
| Meanwhile, industry standards consider voltages under 50 as safe.
|

I thought it was current, or amperage that killed, not voltage ???

On Fri, 04 Apr 2008 12:15:39 GMT, Steven Stone wrote:
In article 19f7705c-4a32-48a5-bfef-fff8053db405
@m44g2000hsc.googlegroups.com, says...
|On Apr 2, 6:14 am, wrote:
| We can agree to disagree on what we each think is safe.
|
| Meanwhile, industry standards consider voltages under 50 as safe.
|

I thought it was current, or amperage that killed, not voltage ???

50 volts genreally can't push enough amps through you to kill you. It's
like you're saying "I thought it was the wetness of water that kills,
not the depth" when someone's saying it's really tough to drown in 3cm
of water.

--
A way of life that is odd or even erratic but interferes with no rights or
interests of others is not to be condemned because it is different.
-- Chief Justice Warren E. Burger

On Thu, 3 Apr 2008 14:35:31 -0700 (PDT) w_tom wrote:

wt Every post about Tivo motherboard electrocution identifies a poster
wt who is in total denial of basic electrical facts. Nothing on that
wt motherboard will electrocute anyone. Why so many posts advocating
wt myths?
....
wt How many are so foolish as to argue that 12 volts can kill?

Oh, 12 V will easily kill you if the wattage is right and it hits the
heart. Alternating the current is also a factor since it will interfere
with the regularly scheduled heartbeats, by the way.

Whether the Tivo in particular is dangerous is not the point, but I will
note that if any working device has AC coming in from the wall, at least
the transformer is dangerous, even if you think the device is off. I
once melted a piece of a flat-head screwdriver's tip off when I poked
inside a computer that appeared to be off. It was a very memorable
lesson.

Please don't mislead people into getting hurt. If you're trolling, it's
stupid to endanger someone's life for fun.

See http://pchem.scs.uiuc.edu/pchemlab/electric.htm for more about the
dangers of electrical currents.

Ted

On Apr 4, 10:31 am, Ted Zlatanov wrote:
Oh, 12 V will easily kill you if the wattage is right and it hits the
heart. Alternating the current is also a factor since it will interfere
with the regularly scheduled heartbeats, by the way.

Whether the Tivo in particular is dangerous is not the point, but I will
note that if any working device has AC coming in from the wall, at least
the transformer is dangerous, even if you think the device is off.

Did you read previous posts before posting myths? If 12 volts kills,
a largest 12 volt current source massacres unsuspecting mechanics.
You have just proven a car battery will electrocute humans. At what
point will the technically naive stop posting this myth.

There is no 'transformer'. Ted also should have learned this before
posting. Ted, this is reposted only because you *know* and you post
without first reading:
Do not use a finger to find hot parts on a power
supply since that supply will have 300 volt charges

Ted - never jump start a car. As you so well know, that 12 volt
battery will electrocute you. It will not electrocute anyone else.
Others are immune because they read and learn before posting.

Sorry Ted - you are being used as an example of so many here who
forget to learn basic electrical concepts and don't bother to first
read the thread. You are not the only one. Steven Stone also posted
a question already asked and answered. Another poster who does not
read the thread and never answers the OP's questions.

No dangerous voltages exist on a Tivo motherboard. Anyone believing
otherwise should post elsewhere. Responsible posters provide Peter
Bogiatzidis with solutions for a Tivo problem. For example, where is
a Tivo's temperature sensor? Based upon technical knowledge displayed
here, I expect no one will answer his question. But lookout!
Automobile batteries routinely electrocute people. Ted, et al tells
us. Therefore it must be true.

On Fri, 4 Apr 2008 18:00:20 -0700 (PDT) w_tom wrote:

wt On Apr 4, 10:31 am, Ted Zlatanov wrote:
Oh, 12 V will easily kill you if the wattage is right and it hits the
heart. Alternating the current is also a factor since it will interfere
with the regularly scheduled heartbeats, by the way.

Whether the Tivo in particular is dangerous is not the point, but I will
note that if any working device has AC coming in from the wall, at least
the transformer is dangerous, even if you think the device is off.

wt Did you read previous posts before posting myths? If 12 volts kills,
wt a largest 12 volt current source massacres unsuspecting mechanics.
wt You have just proven a car battery will electrocute humans. At what
wt point will the technically naive stop posting this myth.

Note I said "if the wattage is right and it hits the heart." The body's
resistance is normally too high to cause this situation, but if you like
you can calculate the resistance of blood across the heart to convince
yourself a lethal current could be delivered at 12V. I agree that under
normal circumstances, 12V are harmless, but I also think it's a very bad
idea to encourage people to poke inside consumer electronics (icepacks,
really?) without the cautionary statements that you dislike.

wt Ted - never jump start a car. As you so well know, that 12 volt
wt battery will electrocute you. It will not electrocute anyone else.
wt Others are immune because they read and learn before posting.

wt Automobile batteries routinely electrocute people. Ted, et al tells
wt us. Therefore it must be true.

I didn't say any of that. Please don't put words in my mouth. Car
batteries have no interest in delivering current through the person.

It's still not a good idea to screw around with car batteries because of
the risk of explosion (the acid can blow in your face, for instance),
but you're not likely to get electrocuted at least.

Ted

On Apr 7, 12:24 pm, Ted Zlatanov wrote:
Note I said "if the wattage is right and it hits the heart." The body's
resistance is normally too high to cause this situation, but if you like
you can calculate the resistance of blood across the heart to convince
yourself a lethal current could be delivered at 12V. I agree that under
normal circumstances, 12V are harmless, but I also think it's a very bad
idea to encourage people to poke inside consumer electronics (icepacks,
really?) without the cautionary statements that you dislike.

Any post about electrocution by a Tivo motherboard using a damp
icepack is ... at what point does the word "context" have any
meaning? Your post again hypes fear of something not dangerous AND
provides the OP with no useful information. So you post same
irrelevance again?

Notice how many are killed uselessly by something with hundreds of
times more wattage. We are told to never jump start a wet car due to
thousands killed by wetness and that high power. Oh. The annual
death count is zero? No such warning exists? People routinely jump
start cars in the rain? Funny how myths get started once someone
forgets reality and does not bother to learn facts. A damp icepack
touching a Tvio motherboard will not electrocute anyone and will not
harm Tivo electronics. Ted - please stop hyping fear, promoting junk
science, and ignoroing context - the OPs problem.

On Mon, 7 Apr 2008 19:25:34 -0700 (PDT) w_tom wrote:

wt On Apr 7, 12:24 pm, Ted Zlatanov wrote:
Note I said "if the wattage is right and it hits the heart." The body's
resistance is normally too high to cause this situation, but if you like
you can calculate the resistance of blood across the heart to convince
yourself a lethal current could be delivered at 12V. I agree that under
normal circumstances, 12V are harmless, but I also think it's a very bad
idea to encourage people to poke inside consumer electronics (icepacks,
really?) without the cautionary statements that you dislike.

wt Any post about electrocution by a Tivo motherboard using a damp
wt icepack is ... at what point does the word "context" have any
wt meaning? Your post again hypes fear of something not dangerous AND
wt provides the OP with no useful information. So you post same
wt irrelevance again?

wt Notice how many are killed uselessly by something with hundreds of
wt times more wattage. We are told to never jump start a wet car due to
wt thousands killed by wetness and that high power. Oh. The annual
wt death count is zero? No such warning exists? People routinely jump
wt start cars in the rain? Funny how myths get started once someone
wt forgets reality and does not bother to learn facts. A damp icepack
wt touching a Tvio motherboard will not electrocute anyone and will not
wt harm Tivo electronics. Ted - please stop hyping fear, promoting junk
wt science, and ignoroing context - the OPs problem.

I'm tired of arguing with things I didn't say, and of restating what I
did say.

You keep bringing up topics I didn't to promote your own argument (straw
man arguments): car battery electrocution and dangers of the 12V from
the Tivo motherboard. You're welcome to do it, but don't tell *me* I'm
hyping fear or junk science. Prove to me that:

1) 12V across the heart will not generate enough current to kill a
person. You can calculate the resistance of a saline solution across
50cm at 23 degrees celsius for the purposes of this exercise, unless you
can stab yourself with probes deeply enough (I'll allow it). I include
my original statement for your reference:

"Oh, 12 V will easily kill you if the wattage is right and it hits the
heart. Alternating the current is also a factor since it will interfere
with the regularly scheduled heartbeats, by the way."

2) I ever said there was a danger from the Tivo motherboard. I include
my original statement for your reference:

"Whether the Tivo in particular is dangerous is not the point, but I will
note that if any working device has AC coming in from the wall, at least
the transformer is dangerous, even if you think the device is off."

I *still* think your advice is cavalier and your disregard for
cautionary statements is troubling. I'm not the only one, apparently.
That's why I posted originally, and I think (2) is relevant to the
discussion though you don't. (1) was an aside, and if you don't like
it, too bad and welcome to Usenet.

Ted