The Bermuda TVriangle
N. Thornton
A customer gets 4 used TVs from dealer B, one after the other. Every
one of them dies within a week, thats the reason for the replacements.
Customer A is pretty unhappy with dealer B, blaming their duff
products.
Customer A goes to dealer C, and tells story of woe. Customer wants a
TV, but is understandably afraid to buy. Dealer C offers to do 2
things:
1. investigate their house to search for any possible cause for this,
and if none is found,
2. to offer 3 month guarantees with any used set sold. Any fault on
the set, full refund.
So, the house survey reveals no cause. No cat peeing, no vase of
flowers on the TV, no damp problem, no TV falling off its stand, no
rugs to put on the TV vent grills, no sign of deranged inhabitants, no
diesel generator, no invertor, no spraying with water based aerosols,
nothing. So customer goes home with dealer C's guaranteed used TV.
Dealer C is full of confidence, both thinking that dealer A must have
been a badun.
But things are not as they seem. After 3 days a call comes in: the TV
doesn't work. Van dispatched with replacement TV, and the faulty one
is subject to thorough examination back at dealer C's premises. Again,
no external issues are found. No damp, no patch marks, no smell of cat
pee, no screws undone, no scratches from the TV being knocked about,
nothing.
With in a week, another call. TV number 6 is dead now. Feeling that
sinking feeling, the van is dispatched one last time. We have no
replacement TV in stock, we'll get yours done within 2 days.
Same examination, and again no cause found. Dealer C decides at this
point to refund the money, and advises customer to rent instead, from
their main competitor.
The only data I dont have is the failure modes for TVs 5 and 6. To
this day no-one knows why those 6 TVs died. What could have happened
in this tale of the Bermuda TVriangle?
Regards, NT
sPoNiX
>The only data I dont have is the failure modes for TVs 5 and 6. To
>this day no-one knows why those 6 TVs died. What could have happened
>in this tale of the Bermuda TVriangle?
What were the failures of sets 1-4? When you say the sets "died" are
they actually dead as in no picture or sound?
sPoNiX
Sir Charles W. Shults III
help that way.
Cheers!
Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
Jason D.
>Hi. A true life conundrum for you.
>
>
>A customer gets 4 used TVs from dealer B, one after the other. Every
>one of them dies within a week, thats the reason for the replacements.
>Customer A is pretty unhappy with dealer B, blaming their duff
>products.
>
No models & brands? No description of fault and what was failed
parts?
There are no mystery IMHO. There is external causes if there is
string of duds in a row. Faulty electrical circuit (house),
lightning, dealer's shoddy tv shop; rare but happens, faulty equipment
hooked to that TV or user. Even shipper can be a problem.
Cheers,
Wizard
klmok
>Hi. A true life conundrum for you.
>
>
>Same examination, and again no cause found. Dealer C decides at this
>point to refund the money, and advises customer to rent instead, from
>their main competitor.
>
>
Try adding a surge protector on the power cord and add a stick-on seal
to that connection to prevent tampering. At least the dealer can
determine if power spikes is a cause. What about the polarity of the
power plugs?
Jeff Liebermann
>A customer gets 4 used TVs from dealer B, one after the other. Every
>one of them dies within a week, thats the reason for the replacements.
>Customer A is pretty unhappy with dealer B, blaming their duff
>products.
I should point out that this story smells like a hoax because of the
lack of make, model, and numerical details. However, I'll treat it
seriously (for no obvious reason). I also don't know of any dealer
that would replace 4ea TV's under warranty. One is the norm, two for
good customers, but not three replacements.
It would have been helpful if you supplied some details such as the TV
makes and models, as well as the results of any post mortem analysis.
Some clues as to the exact desciption of "dead" would be helpful.
I'll assume that the sets are dead as in no power supply or no
picture. A short list of possibles are:
1. Major power glitches via the AC power.
2. Faulty ground on AC power.
3. Static electricity fries circuitry when touched.
4. Ionizing (nuclear) radiation breaks down circuitry. Is the owner a
nuclear power station employee that takes his work home?
5. EMP (Electro Magnetic Pulse). Proximity to large pulsed RF power
such as high power RADAR.
6. EMF (Electro Magentic Field). Proximity to a large magnetic or
electric field such as the transformer on an X-ray machine.
7. High voltage. Is there an operational Tesla coil in the house?
8. High power microwaves. Is someone experimenting with a microwave
oven with the interlock disabled and pointed at the TV set?
--
Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
(831)421-6491 pgr (831)336-2558 home
http://www.LearnByDestroying.com AE6KS
je...@comix.santa-cruz.ca.us je...@cruzio.com
ch...@nospam.com
Bad neutral connection in the panel, causing the voltage to swing up?
AC or DC voltage on the antenna connection?
petrus bitbyter
"N. Thornton" <big...@meeow.co.uk> schreef in bericht
news:a7076635.03090...@posting.google.com...
LS,
Havig no real information about this case, we can speculate through all
eternity. Here is one: Did the customer have the bad habit of switching the
set off and on rapidly? A lot of TVsets, even new ones, will not survive
this treatment for long.
pieter
---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.511 / Virus Database: 308 - Release Date: 18-8-2003
N. Thornton
I'll answer you all as best I can. I know many details, but not all.
>What were the failures of sets 1-4? When you say the sets "died" are
>they actually dead as in no picture or sound?
I never saw them so dont know. That would certainly be useful data. I
saw sets 5 and 6, and there was no sign of life, nothing. I got to see
them enough to see there was no tampering, peeing, spilling, etc, but
thats all.
>No models & brands?
No, they were assorted used 24" sets, various makes.
> No description of fault and what was failed parts?
Only info I have is they were all 'dead', no sign of life. Might
suggest a power issue - but loptr failure was more common than PSU
fails on those (discrete component) TVs. And a shorted loptr would
take down the psu.
>There are no mystery IMHO. There is external causes if there is
>string of duds in a row.
I agree. If we go with a normal expected failure rate of 20%, the odds
of it being chance are 1 in 15000.
>Faulty electrical circuit (house),
I understand that could fry stuff in the US, but it could only cause
Vdrop here, which should be harmless.
>lightning,
have to be a heck of a lot of it! I think thats most unlikely. Their
house wiring would be charcoal by the time 6 sets had gone, ditto the
neighbours.
> dealer's shoddy tv shop;
The first supplier may well have been, but I know enough of this case
to know they were thorough second time round. Sets 5,6 came from a
sound dealer.
>rare but happens, faulty equipment
>hooked to that TV
Good point. But... I cant see any way a video could damage a TV. There
are no other external connections on those old sets. Putting mains up
the aerial socket would be harmless to the TV. The input capacitors
would just sit and smile.
> or user.
Prime suspect! But how? No-one could figure anything.
> Even shipper can be a problem.
Maybe so for sets 1-4, but not 5,6. I knew the business involved, the
2nd dealer, and was asked in to help de-mysterise, without success.
Both sets 5 and 6 were checked at installation.
>Try adding a surge protector on the power cord and add a stick-on
seal
>to that connection to prevent tampering. At least the dealer can
>determine if power spikes is a cause.
I think power spikes are not a problem, any consumer equipment has
sufficient filtering built in to protect itself. Especially stuff like
TVs and puters. Surge protectors have little effect by comparison. The
house was on a big estate, so any problems would have been shared all
round.
> What about the polarity of the
>power plugs?
wouldn't make any difference AFAICS.
>I should point out that this story smells like a hoax because of the
>lack of make, model, and numerical details.
We're talking low cost used sets, so no-one cared what make and model
they were. It was just screen size and decade of manufacture that
counted.
> I also don't know of any dealer
>that would replace 4ea TV's under warranty. One is the norm, two for
>good customers, but not three replacements.
Good point. The customer was really not the smart kind, so may well
have bought 2 of the first 4 sets, the other 2 being replacements for
those. But I dont really know. They could even have paid for 3 or 4.
>It would have been helpful if you supplied some details such as the
TV
>makes and models, as well as the results of any post mortem analysis.
I dont really have any more to give you. Second hand dealers dont
investigate things the way a manufacturer would. If the customer keeps
bringing stuff back, they dont serve em anymore. Thats it.
>Some clues as to the exact desciption of "dead" would be helpful.
>I'll assume that the sets are dead as in no power supply or no
>picture.
yup.
>1. Major power glitches via the AC power.
It would have to be truly major, and the house was on the same grid as
its neighbours: I did say look for generators, autotransformers etc,
nothing. Nor any evidence of anyone at the house who might have a clue
about anything like that. They really weren't the bright type.
>2. Faulty ground on AC power.
would make no difference here.
>3. Static electricity fries circuitry when touched.
Those sets aren't static sensitive AFAIK. Static on the cabs was
normal anyway, and never caused trouble.
>4. Ionizing (nuclear) radiation breaks down circuitry. Is the owner
a
>nuclear power station employee that takes his work home?
hehe, good one - though it sounds pertty unlikely. :) This guy was no
brainiac or anything.
>5. EMP (Electro Magnetic Pulse). Proximity to large pulsed RF power
>such as high power RADAR.
on a large housing estate, so pretty unlikely.
>6. EMF (Electro Magentic Field). Proximity to a large magnetic or
>electric field such as the transformer on an X-ray machine.
Nothing was found... would have to have been a fair distance away.
> 7. High voltage. Is there an operational Tesla coil in the house?
I did wonder, but no-one there showed anything like enough
intelligence to do something like that, and absolutely no sign of
anything suggesting any interest in electrics or tronics was found.
>8. High power microwaves. Is someone experimenting with a microwave
>oven with the interlock disabled and pointed at the TV set?
You never know! But a) its most unlikely, b) one would expect medical
consequences, and c) nothing was found to indicate any form of
electrical work/play of any kind at all.
>Bad neutral connection in the panel, causing the voltage to swing up?
The UK isnt wired like that, so we dont get that problem.
Well, certainly some interesting ideas there, but I can't help
thinking the possibles are all very unlikely.
I half wondered about a malicious or sociopathic teenage neighbour
equipped with something homebrewed and dangerous, but lets face it,
its extremely unlikely, and I cant even think what apparatus would do
it.
I'm still mysterised. Maybe news2020 was right after all :)
Regards, NT
Jason D.
Hi, Whew long one!
>I'll answer you all as best I can. I know many details, but not all.
>
>>What were the failures of sets 1-4? When you say the sets "died" are
>>they actually dead as in no picture or sound?
>
>I never saw them so dont know. That would certainly be useful data. I
>saw sets 5 and 6, and there was no sign of life, nothing. I got to see
>them enough to see there was no tampering, peeing, spilling, etc, but
>thats all.
>
>>No models & brands?
>
>No, they were assorted used 24" sets, various makes.
Uggh... I don't like this...!
Why is your job reported this without all the details, you gotta have
the paperwork with serial and models on them when they came in for
checks and estimate or warrenty repairs?
>> No description of fault and what was failed parts?
>
>Only info I have is they were all 'dead', no sign of life. Might
>suggest a power issue - but loptr failure was more common than PSU
>fails on those (discrete component) TVs. And a shorted loptr would
>take down the psu.
That's useless info to go on.
>I agree. If we go with a normal expected failure rate of 20%, the odds
>of it being chance are 1 in 15000.
>
>>Faulty electrical circuit (house),
>
>I understand that could fry stuff in the US, but it could only cause
>Vdrop here, which should be harmless.
>>lightning,
>
>have to be a heck of a lot of it! I think thats most unlikely. Their
>house wiring would be charcoal by the time 6 sets had gone, ditto the
>neighbours.
Doesn't matter where 1v or 4kV as power sources. they all get fried
if lightning hits. Seen many of those.
But series of duds in a row is very suspicious and must be carefully
analyzed which means opening up the sets and take a look and note the
models. Frankly, I'm disappointed with this because we still have
nothing to go on so far.
>> dealer's shoddy tv shop;
>
>The first supplier may well have been, but I know enough of this case
>to know they were thorough second time round. Sets 5,6 came from a
>sound dealer.
>
>>rare but happens, faulty equipment
>>hooked to that TV
>
>Good point. But... I cant see any way a video could damage a TV. There
>are no other external connections on those old sets. Putting mains up
>the aerial socket would be harmless to the TV. The input capacitors
>would just sit and smile.
Considered that? Intermittent house's open neutral wire especially in
cheap sets that has hot ground throughout the chassis, so power went
through wrong paths through RF connector or video inputs.
But I don't know what system is like for western 230V.
>Prime suspect! But how? No-one could figure anything.
>
This is EXACTLY the reason to dig deeper into those dud sets.
>> Even shipper can be a problem.
>
>Maybe so for sets 1-4, but not 5,6. I knew the business involved, the
>2nd dealer, and was asked in to help de-mysterise, without success.
>Both sets 5 and 6 were checked at installation.
Okay that is small step.
>I think power spikes are not a problem, any consumer equipment has
>sufficient filtering built in to protect itself. Especially stuff like
>TVs and puters. Surge protectors have little effect by comparison. The
>house was on a big estate, so any problems would have been shared all
>round.
Localized surges can happen if the power is shared with other massive
items that inductively switch out and in rapidly. Pow!
>>power plugs?
>
>wouldn't make any difference AFAICS.
That depends on specific chassis. Few crappiest chassis had one diode
instead of bridge rectifier. The neutral is the shared cold/hot
ground. Reversed outlet may be a problem.
>We're talking low cost used sets, so no-one cared what make and model
>they were. It was just screen size and decade of manufacture that
>counted.
Doesn't matter. 24" is almost the bottom end but we still charge
decent money on those. FYI: N. Amcerican TV's is 25" and "worthy
doing" but to you it is 24". 20" & 19" is too cheap here, we don't
spend too much time on 13" it is disposeable.
>>It would have been helpful if you supplied some details such as the
>TV
>>makes and models, as well as the results of any post mortem analysis.
>
>I dont really have any more to give you. Second hand dealers dont
>investigate things the way a manufacturer would. If the customer keeps
>bringing stuff back, they dont serve em anymore. Thats it.
Then dealer is not doing the job, they must find out WHY and make the
customer happy this means they must drop these sets into your hands,
this means dealer chasing money which IHMO bit sleazy.
>>1. Major power glitches via the AC power.
>
>>6. EMF (Electro Magentic Field). Proximity to a large magnetic or
>>electric field such as the transformer on an X-ray machine.
This will make pix MOVE around like wild. I saw that when I rode on a
linear motor trolley lab demo, they had test equipments hooked up
using pc monitors. Wow, really cool to see the pix move around and
feel the hum of motor in sync with that at same time.
>>Bad neutral connection in the panel, causing the voltage to swing up?
>
>The UK isnt wired like that, so we dont get that problem.
>I'm still mysterised. Maybe news2020 was right after all :)
Well, I had seen one once, errant loose staple inside a late model
(citizen) flat CRT combo tv/vcr kept shutdown, the SMPS is smart
design and sensitive so there wasn't a blow up at all. Took that bit
off between the magnetic biased inductor pin and ground pan. TV
started working fine.
>Regards, NT
Cheers,
Wizard
Nigel
faulty sub-station (in Leicester) that was kicking out 275v pretty much all
the time, instead of 240v.
It was only proved after the electricity company arranged for a voltage/time
measurement recorder to be fitted into the house for a few days.
"N. Thornton" <big...@meeow.co.uk> wrote in message
news:a7076635.03090...@posting.google.com...
James Sweet
particular appliance came on the line voltage rose.
"N. Thornton" <big...@meeow.co.uk> wrote in message
news:a7076635.03090...@posting.google.com...
N. Thornton
I hadn't planned to become quizmaster, but it seems I have :) Lets see
what bits I can fill in.
>>>No models & brands?
>>No, they were assorted used 24" sets, various makes.
>Uggh... I don't like this...!
>
>Why is your job reported this without all the details, you gotta have
>the paperwork with serial and models on them when they came in for
>checks and estimate or warrenty repairs?
A dealer of cheap used sets isnt interested in all that. A bit of
paper stuck on them saying 'Joe tripler £30' was as far as paperwork
went. Its a very different scene to say a manufacturer. No-one would
be writing down serial numbers.
Re warranty returns it makes more sense to swap them. 'OK, sorry bout
that, it can happen occasionally. These are the £30 ones here, help
yourself.' Saves a lot of muck about, and keeps customers happy with
instant service. The return just goes on the supply pile, no rush.
>But series of duds in a row is very suspicious and must be carefully
>analyzed which means opening up the sets and take a look and note the
>models. Frankly, I'm disappointed with this because we still have
>nothing to go on so far.
6 assorted sets died, so I doubt the exact models make that much
diference. Tho I agree it would be nice to know, they might all share
a feature.
>>>rare but happens, faulty equipment
>>>hooked to that TV
>>Good point. But... I cant see any way a video could damage a TV.
There
>>are no other external connections on those old sets. Putting mains
up
>>the aerial socket would be harmless to the TV. The input capacitors
>>would just sit and smile.
>Considered that? Intermittent house's open neutral wire especially
in
>cheap sets that has hot ground throughout the chassis, so power went
>through wrong paths through RF connector or video inputs.
>But I don't know what system is like for western 230V.
The only connector on those old sets is the aerial plug. They use very
thick insulators in the way: nothing is ever going through there
except UHF. So basically this is impossible.
>>>customer
>>Prime suspect! But how? No-one could figure anything.
>This is EXACTLY the reason to dig deeper into those dud sets.
I agree, from our point of view. But this was a business, they just
moved on. They could have fixed several sets in the time it would have
taken to get to the bottom of it.
And there's always a small percentage of nutty customers anyway, who
buy stuff and do weird things with it, then complain that it doesn't
work. Getting rid of them is the only sensible option.
>>>power plugs?
>>wouldn't make any difference AFAICS.
>That depends on specific chassis. Few crappiest chassis had one
diode
>instead of bridge rectifier. The neutral is the shared cold/hot
>ground. Reversed outlet may be a problem.
I can't see how it would make any difference. I assume all those sets
were live chassis, and in at least most cases bridge rectifier from
mains to chassis. Whether BR or diode... perhaps you can explain a
failure mechanism.
>>We're talking low cost used sets, so no-one cared what make and
model
>>they were. It was just screen size and decade of manufacture that
>>counted.
>Doesn't matter. 24" is almost the bottom end but we still charge
>decent money on those. FYI: N. Amcerican TV's is 25" and "worthy
>doing" but to you it is 24". 20" & 19" is too cheap here, we don't
>spend too much time on 13" it is disposeable.
Yup. It was the other way round there, with the big old 24"ers being
cheaper cos they were such elepants. People mainly wanted 19"s. We
have much smaller houses here on the whole.
>>I dont really have any more to give you. Second hand dealers dont
>>investigate things the way a manufacturer would. If the customer
keeps
>>bringing stuff back, they dont serve em anymore. Thats it.
>Then dealer is not doing the job, they must find out WHY and make the
>customer happy this means they must drop these sets into your hands,
>this means dealer chasing money which IHMO bit sleazy.
The dealer is just there to make a living, its his job. The dealer
went out of his way to create a happy customer, but to no avail. I've
never come across a second hand equipment dealer who would go to the
lengths you suggest. They'd soon be out of business.
>Perhaps they had a loose neutral connection somewhere so that when a
>particular appliance came on the line voltage rose.
The UK isn't wired like that, no V_rise is possible that way. Our
supply is 240v, not 120-0-120. Loads can only cause V_drops.
>eternity. Here is one: Did the customer have the bad habit of
switching the
>set off and on rapidly? A lot of TVsets, even new ones, will not
survive
>this treatment for long.
Good point, one of the kids might have. I'll ask you for a failure
mechanism tho, as I cant think how it would fry anything.
>While attempting to allign a friends TV some years ago I touched the
antenna
>to earth ground and cooked the tuner resulting in no picture or
sound.
>This wrote off the TV.
>
>One possible reason that these TVs failed is that there may have been
a path
>to ground through a cable Connection.
Normally the antenna connection is very heavily insulated from the
chassis on both poles. You could put a kV on there and nothing should
happen. I'm surprised yours died. It would be very different if you
had baseband connectors, but with UHF aerial only, the thing should be
virtually bullet proof.
>The last time I had a serial equipment killer like that, it was due
to a
>faulty sub-station (in Leicester) that was kicking out 275v pretty
much all
>the time, instead of 240v.
>
>It was only proved after the electricity company arranged for a
voltage/time
>measurement recorder to be fitted into the house for a few days.
ahhhh! Presumably tho much of the estate would have had the same
problem, if that was the cause.
In fact, on second thoughts, I'm not so sure. Junkers routinely had
their PSUs set to the 220v setting when the tube was crap, and
sometimes 200v to get the picture watchable. That would up the V
throughout the set, heater, EHT, everything, yet they survived OK. 240
on 200v is +20% too high, 275 on 240 is only 14.6%. So I'm not
convinced yet that would account for 6 rapidly dead sets, but
possibly.
This all happened years ago, and I still dont have an explanation I'm
really convinced by. Its odd.
Regards, NT
N. Thornton
>>>No models & brands?
>>>customer
>>>power plugs?
>The last time I had a serial equipment killer like that, it was due
to a
>faulty sub-station (in Leicester) that was kicking out 275v pretty
much all
>the time, instead of 240v.
>
>It was only proved after the electricity company arranged for a
voltage/time
>measurement recorder to be fitted into the house for a few days.
ahhhh! Presumably tho much of the estate would have had the same
Nigel
>The last time I had a serial equipment killer like that, it was due
to a
>faulty sub-station (in Leicester) that was kicking out 275v pretty
much all
>the time, instead of 240v.
>
>It was only proved after the electricity company arranged for a
voltage/time
>measurement recorder to be fitted into the house for a few days.
ahhhh! Presumably tho much of the estate would have had the same
problem, if that was the cause.
--------------------------------------------------------------------
No, bizarrely enough, the problem was isolated to one street in one suburb
and no other equipment owned by our customer expired in suspicious
circumstances. To the best of our knowledge at the time, none of the
neighbours experienced problems with any equipment.
Dave VanHorn
if i had to guess, low voltage.
Jim Thompson
<james...@hotmail.com> wrote:
>Perhaps they had a loose neutral connection somewhere so that when a
>particular appliance came on the line voltage rose.
>
[snip]
A very good possibility.
In 1993, while I was working in Europe, our oldest daughter was
house-sitting for us.
When we returned she told us that, when using our shower, it sometimes
felt like an electrical shock.
A little metering revealed 15VAC between the shower head and the
drain.
In Arizona "ground" is established by bonding water pipes to incoming
neutral (but not the sewer piping).
I also noticed that some lights would brighten and some would dim when
the A/C came on.
A call to the power company got us an instant temporary neutral while
they dug up the underground feed.
In our newest house I personally added local bonding between the
shower piping and the metal part of the drain before the floors were
poured.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Tony Williams
Dave VanHorn <dvan...@cedar.net> wrote:
> if i had to guess, low voltage.
We have experienced a tv failure during an extended
browndown (and recovery). The Telefunken tv that
replaced it had a built in latching relay on the mains.
--
Tony Williams.
Zak
> When we returned she told us that, when using our shower, it sometimes
> felt like an electrical shock.
>
> A little metering revealed 15VAC between the shower head and the
> drain.
>
> In Arizona "ground" is established by bonding water pipes to incoming
> neutral (but not the sewer piping).
Aagh!
Around here (Netherlands) ground and neutral are totally different
things. Consumers are not supposed to be interested in which of the plug
pins is neutral; could even be 2 x 115 volts in some places.
The installer is supposed to know what is hot - that's the side the
light switch goes on.
Still goes wrongs sometimes: last case making the paper was a 'ring
ground' connecting different houses to a single ground pen someplace -
which had failed.
Then there's folks putting a srew from the lamp fixture below into a
shower drain, causing leak, wetness, and leakage. Not good.
OTOH all metal objects in bathroom space need to be wired together in a
way that is easy to inspect - at least for newly built homes.
Connecting ground to water is also not allowed for new buidings. A
separate ground pin in the earth, wired to a separate net in the home,
is what it should be. Never connected to neutral.
Where do people connect neutral to ground by design?
Thomas
Jim Thompson
I think I've confused you with neutral, which around here is supposed
to be "ground". Then there's "common" which is like ground but not
connected to ground ;-)
Jim Thompson
And I should have added, "earth" is Arizona is not adequate to call
ground... the water table is several hundred feet down :-(
Dave VanHorn
"Tony Williams" <to...@ledelec.demon.co.uk> wrote in message
news:4c2bb1f...@ledelec.demon.co.uk...
we used to live in an area with voltage as low as 70v.
i have several power strips now, with dropout relays that i wired into them.
you turn them on, then off. when the voltage droops, they kick out, and stay
there.
James Sweet
> >Perhaps they had a loose neutral connection somewhere so that when a
> >particular appliance came on the line voltage rose.
>
> The UK isn't wired like that, no V_rise is possible that way. Our
> supply is 240v, not 120-0-120. Loads can only cause V_drops.
>
>
James Sweet
>
> we used to live in an area with voltage as low as 70v.
> i have several power strips now, with dropout relays that i wired into
them.
> you turn them on, then off. when the voltage droops, they kick out, and
stay
> there.
>
>
70v? Is that on a 120v line or 240? Either way that's a big enough drop that
I would think a call to the utility would get it fixed up in short order.
James Sweet
>
> Connecting ground to water is also not allowed for new buidings. A
> separate ground pin in the earth, wired to a separate net in the home,
> is what it should be. Never connected to neutral.
>
> Where do people connect neutral to ground by design?
>
>
> Thomas
>
In north america the netral and ground wires all connect to the same bus in
the service panel which is then grounded to a rod in the earth. Two hot
wires come in, one to each side of the panel forming two busses, between
either one and ground is 120v which is what most branch circuits are and
between the two is 240v which is used for heavier loads.
Tony Williams
Dave VanHorn <dvan...@cedar.net> wrote:
> we used to live in an area with voltage as low as 70v.
> i have several power strips now, with dropout relays that i wired
> into them. you turn them on, then off. when the voltage droops,
> they kick out, and stay there.
Our frequent browndown problems are caused by long runs of
overhead wires and squirrels. Anything with a switcher in
it is now powered off some sort of latching contactor.
--
Tony Williams.
Active8
says...
> Perhaps they had a loose neutral connection somewhere so that when a
> particular appliance came on the line voltage rose.
or a 3-phase appliance with a fault on one phase causing weird stuff.
mike
Active8
will-get-you.com says...
> On Tue, 02 Sep 2003 06:27:00 GMT, "James Sweet"
> <james...@hotmail.com> wrote:
>
> >Perhaps they had a loose neutral connection somewhere so that when a
> >particular appliance came on the line voltage rose.
> >
> [snip]
>
> A very good possibility.
>
> In 1993, while I was working in Europe, our oldest daughter was
> house-sitting for us.
>
> When we returned she told us that, when using our shower, it sometimes
> felt like an electrical shock.
a friend wasb geting zapped from the shower fixtures. telco subscriber
side lines rubbing water pipes under the house. nice, eh?
brs,
mike
Active8
> >I think power spikes are not a problem, any consumer equipment has
> >sufficient filtering built in to protect itself. Especially stuff like
> >TVs and puters. Surge protectors have little effect by comparison. The
> >house was on a big estate, so any problems would have been shared all
> >round.
>
> Localized surges can happen if the power is shared with other massive
> items that inductively switch out and in rapidly. Pow!
that's one of the first suspects that came to mind when i started
reading this thread. i can picture a house with crappy wiring blowing
stuff up when the washing machine's running. 5 used sets that have
possibly had the power circuits worked over and maybe a filter screwing
up or some other power prob. i'd have wanted a chart recorder on it
after the 2nd set went south. at least on a power prob like no pic/no
sound/obvious x-ray detect shut-down.
or a bad cockroach problem :-0 bunch of filthy old sets?
[snip]
>
> Well, I had seen one once, errant loose staple inside a late model
> (citizen) flat CRT combo tv/vcr kept shutdown, the SMPS is smart
> design and sensitive so there wasn't a blow up at all. Took that bit
> off between the magnetic biased inductor pin and ground pan. TV
> started working fine.
i found a foam packing peanut in a cheap combo once. that was an easy
$25 for a gear reset and a quick check w/ lite cleaning.
>
> >Regards, NT
>
> Cheers,
>
> Wizard
>
Active8
> Jim Thompson wrote:
>
> > When we returned she told us that, when using our shower, it sometimes
> > felt like an electrical shock.
> >
> > A little metering revealed 15VAC between the shower head and the
> > drain.
> >
> > In Arizona "ground" is established by bonding water pipes to incoming
> > neutral (but not the sewer piping).
>
> Aagh!
>
> Around here (Netherlands) ground and neutral are totally different
> things. Consumers are not supposed to be interested in which of the plug
> pins is neutral; could even be 2 x 115 volts in some places.
and then there's polarized plugs... even on some old lamps.
>
> The installer is supposed to know what is hot - that's the side the
> light switch goes on.
>
> Still goes wrongs sometimes: last case making the paper was a 'ring
> ground' connecting different houses to a single ground pen someplace -
> which had failed.
ring ground for housing. that's a new one on me. of all crackheaded
ideas!
>
> Then there's folks putting a srew from the lamp fixture below into a
> shower drain, causing leak, wetness, and leakage. Not good.
>
> OTOH all metal objects in bathroom space need to be wired together in a
> way that is easy to inspect - at least for newly built homes.
i forgot to wire in the toilet paper holder. will i fry?
> Connecting ground to water is also not allowed for new buidings.
i'd have never, since age of maybe 6 when i understood electric shock
from ben franklin's kite, ever thought of designing a lightning rod out
of some poor schmuck's plumbing. nowdays, of course, they're running
plastic water hose out of plastic manifolds at the entry.
as long as i'm not showering on a ground rod, i'm ok.
> A
> separate ground pin in the earth, wired to a separate net in the home,
> is what it should be. Never connected to neutral.
>
> Where do people connect neutral to ground by design?
in USA a new load center box's earth/safety bus is bonded to the rod and
jumpered to the neutral bus. trust me, that's good practice, thus the
code.
old house wiring is always suspect.
towns with delta systems powering old neighborhoods where the houses are
totally rigged up messes... scary.
you can be an out of town landlord with crap everything.
the govt has programs to help bring wiring up to code under different
housing programs. i like that.
brs,
mike
>
>
> Thomas
>
>
Active8
>
> And I should have added, "earth" is Arizona is not adequate to call
> ground... the water table is several hundred feet down :-(
>
> ...Jim Thompson
>
in Pensacola, Fla., ground rods disappear into the void with a coupla
hits. pray for rain. N. Carolina... you can pull screw anchors out of
the ground just trying to tension a down guy.
brs,
mike
Frank Bemelman
news:MPG.19bf6c6a8...@news.east.earthlink.net...
> In article <1i75b.1646$P51.5015@amstwist00>, Z...@spam.invalid says...
> >
> > way that is easy to inspect - at least for newly built homes.
>
> i forgot to wire in the toilet paper holder. will i fry?
Difficult to tell. Depends whether you have wired the
hinges of your toilet seat ;)
--
Thanks,
Frank Bemelman
(remove 'x' & .invalid when sending email)
N. Thornton
>> Localized surges can happen if the power is shared with other
massive
>> items that inductively switch out and in rapidly. Pow!
Active8:
>that's one of the first suspects that came to mind when i started
>reading this thread. i can picture a house with crappy wiring blowing
>stuff up when the washing machine's running.
The house was recently built, no visible alterations. Both washing
machines and TVs have suficient filtering built in to avoid such
damage: both would have to be wired over, _and_ a high impedance
inserted to the rest of the supply and loads before this would kill
sets. I cant see it.
>or a bad cockroach problem :-0 bunch of filthy old sets?
they were dirty inside, but even so the failure rate was still 20%,
which pans out at 1 in 15,000 for 6 sets to die by chance. I suppose
its not quite impossible.
cockroaches... the house was clean and modern, again I can't see it.
>Where do people connect neutral to ground by design?
>Thomas
Here in Britain a lot of our supplies are like that, its caled PME, or
protective multiple earthing. The power co earths neutral at multiple
locations to make it safe enough for use as a protective earth.
>or a 3-phase appliance with a fault on one phase causing weird stuff.
>mike
good point, but it was a big housing estate, there would have been no
3 phase supplies or loads.
Still stumped. I'm beginning to think it may have been any one of
those rather unlikely (but not impossible) scenarios.
Regards, NT
Frank Bemelman
news:a7076635.03090...@posting.google.com...
>
> Still stumped. I'm beginning to think it may have been any one of
> those rather unlikely (but not impossible) scenarios.
Are these folks watching television now, or did they buy
a tropical fishtank to watch instead? It would be amazing
if all the fish died ;)
Tom Del Rosso
>
> I think I've confused you with neutral, which around here is supposed
> to be "ground". Then there's "common" which is like ground but not
> connected to ground ;-)
Ground is ground
the world around
except in England
where it's earth.
(I'm not saying it's true exactly, but it's an old rhyme I heard.)
--
-Reply in group, but if emailing please add two more zeros and delete
the obvious-
Dave VanHorn
> 70v? Is that on a 120v line or 240? Either way that's a big enough drop
that
> I would think a call to the utility would get it fixed up in short order.
110 line. you'd think so, but it wasn't. everyone in the area had variacs
on their tvs, which they dialed up or down according to the size of the
picture on the screen.
jakdedert
news:1PM4b.7266$Xh6.1...@amsnews02.chello.com...
>
<snip>
>
> Havig no real information about this case, we can speculate through all
> eternity. Here is one: Did the customer have the bad habit of switching
the
> set off and on rapidly? A lot of TVsets, even new ones, will not survive
> this treatment for long.
>
This is unavoidable on many sets these days. The stupid switches are so
sensitive that it's very easy to toggle the set on/off with one quick push.
On almost every TV in my household (six or seven, I've lost count), one must
'very' positively push and hold the switch for a second to turn on or off.
The problem is compounded by the fact that a lot of newer sets have no pilot
light of any kind. The only positive indication of power on is when the CRT
heats up enough to give a display. I've turned on/off/on many times,
because I though I hadn't pushed the switch hard enough the first time.
jak
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.511 / Virus Database: 308 - Release Date: 18-8-2003
>
Walter Harley
news:MPG.19bf6c6a8...@news.east.earthlink.net...
> i forgot to wire in the toilet paper holder. will i fry?
Only if you wipe.
Walter Harley
> which pans out at 1 in 15,000 for 6 sets to die by chance. I suppose
> its not quite impossible.
Intuitively, I'm with you. But still, to play devil's advocate: you'd
expect to see something that happens once in 15k times, every now and then,
if you stay in the field. Calculate the odds of *never* seeing a 1-in-15k
occurrence, if you take (say) 10k samples; how many sets did that shop sell
over the years? And indeed, a relatively rare occurrence is even more
likely to come to your notice than it would by random chance, because it's
more likely to get mentioned. (Thus, we all hear about lottery winners,
even though they are so rare compared to losers.)
Seventh one's the charm! ;-)
Zak
> And I should have added, "earth" is Arizona is not adequate to call
> ground... the water table is several hundred feet down :-(
Yes - that problem exuists here too even though you have to go less deep
than in the desert.
In any case, I understand that there are places where mains return
current and safety ground are tied together somehow. But it may not be
the US...
It is an immensely stupid idea, IMO.
Thomas
James Sweet
"Active8" <mcol...@earthlink.net.invalid> wrote in message
A 3 phase appliance in a home? I've *never* seen 3 phase power in a home
before, would be nice though.
Tom Del Rosso
>
>> Bad neutral connection in the panel, causing the voltage to swing up?
>
> The UK isnt wired like that, so we dont get that problem.
We have center tapped transformers, where the center tap is grounded at
the source. What do you have? Since you use 220-240V I would guess you
don't need a center tap and neither line is grounded.
Zak
> We have center tapped transformers, where the center tap is grounded at
> the source. What do you have? Since you use 220-240V I would guess you
> don't need a center tap and neither line is grounded.
In the Netherlands, the usual setup is 3 phase wiring through the
street. Households get one of the phases and neutral, or, if they want,
all three phases.
One phase to ground: 230 volt. 3 phases: 400 volt between phases.
If the neutral gets disconnected at the transformer station voltages can
go way off - higher or lower, depending on load.
Rarely happens though - the cable is under ground and tends to short,
not open.
I guess it is a matter of economics, with population density. At high
densities, a large neighbourhood transformer makes sense and the would
better be 3 phase, with underground cable.
At lower densities, a 2 phase system (especially constructed on poles,
where an extra phase costs labour to install) with a sinmpler 'pole
transfrmer' may make more sense.
BTW the clamps used to take power off the underground aluminum cables
are nice - a kind of vampire tap, with serrated metal pieces cutting
through the insulation of the (powered) cable. On which the household
side connection is attached, and the whole cast in resin.
Thomas
N. Thornton
I suspect you've nit the hail on the head Walter.
Regards, NT
Laurence Payne
>In the Netherlands, the usual setup is 3 phase wiring through the
>street. Households get one of the phases and neutral, or, if they want,
>all three phases.
Same here in UK, in my street anyway.
3 phases buried in the street. Each house gets one of them.
Watched a bad joint being replaced recently. The isolation box at the
end of the street had jumpers sitting in a wooden frame. Very
Victorian :-)
Active8
says...
mike
Jim Thompson
I had 3-phase electric at my first "new" house in old-town (69th
Place/Oak/Scottsdale Rd.) Scottsdale in 1964-69. Made for the
smoothest running A/C before or since.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Active8
l...@laurenceDELETEpayne.freeserve.co.uk says...
you'd have to get 3-phase to run stuff. kind of a pain for small
craftsmen, etc. like this girl that does pocelain dolls... 3-phase kiln.
mike
Active8
big...@meeow.co.uk says...
> Hi
>
>
> >> Localized surges can happen if the power is shared with other
> massive
> >> items that inductively switch out and in rapidly. Pow!
>
> Active8:
> >that's one of the first suspects that came to mind when i started
> >reading this thread. i can picture a house with crappy wiring blowing
> >stuff up when the washing machine's running.
>
> The house was recently built, no visible alterations. Both washing
> machines and TVs have suficient filtering built in to avoid such
> damage: both would have to be wired over, _and_ a high impedance
> inserted to the rest of the supply and loads before this would kill
> sets. I cant see it.
>
>
> >or a bad cockroach problem :-0 bunch of filthy old sets?
>
> they were dirty inside, but even so the failure rate was still 20%,
> which pans out at 1 in 15,000 for 6 sets to die by chance. I suppose
> its not quite impossible.
>
> cockroaches... the house was clean and modern, again I can't see it.
what about from the previous owner? 6 sets that came out of dive hotels?
i've seen enough out of hotels, nothing really nasty, though. i know if
they were previously rented there's a good chance of roaches. but if
there was no evidence of spillage, i suppose that would mean a good
enough look at the insides to be able to find roaches.
>
> >Where do people connect neutral to ground by design?
> >Thomas
>
> Here in Britain a lot of our supplies are like that, its caled PME, or
> protective multiple earthing. The power co earths neutral at multiple
> locations to make it safe enough for use as a protective earth.
here in US, it's MGN. multi-grounded neutral. that's at the poles or
vaults. the houses get the neutral/earth connection in the load center.
brs,
mike
dmi...@spamblock.demon.co.uk
> N. Thornton wrote:
>>
>>> Bad neutral connection in the panel, causing the voltage to swing up?
>> The UK isnt wired like that, so we dont get that problem.
> We have center tapped transformers, where the center tap is grounded at
> the source. What do you have? Since you use 220-240V I would guess you
> don't need a center tap and neither line is grounded.
Usaually delta-star transformers with the neutral point grounded at the
transformer. 230V from any of the 3 phases to neutral, 400V between
phases.
Sometimes the center tap of the transformer (neutral/Ground) is exported
along the cable armour, and this is used to provide a very low impeadence
'ground' path for any fault current (This is designated in the UK wiring
regs as TN-S).
Some modern installations tie Neutral and ground together at the buildings
incoming terminal point (designated TN-CS), which requires some extra
safety measures (basically the combined neutral/earth must be grounded
at multiple points such that a failiure near the transformer will not
allow dangerous potential differences to develop (or currents to flow
in any given earth conductor). This connection is ALWAYS the
responsibility of the supply company and is not something that the consumer
has any reason to touch. In addition extensive equipotential bonding is
used in these installations to ensure that you cannot touch 2 peices of
metal at different potentials. This gets interesting when you have things
like antannae feed lines connecting to earthed metal masts as in the
event of a fault lots of current can flow to earth via the screen of your
feeder.....
Then there is the TT system, which grounds the transformer star point,
but does not supply an earth to the consumer who must supply their own.
Finally there is the IT system which is totally floating, and can
survive any single fault to earth. This is sometimes used in hospital
operating rooms and the like. These systems are fitted with a warning
system to alert the owners in the event of a fault to earth so that
it can be rectified before another fault creates a dangerous situation.
Regards, Dan.
--
** The email address *IS* valid, do NOT remove the spamblock
And on the evening of the first day the lord said...........
.... LX 1, GO!; and there was light.
Pankajkumar Chauhan
> In sci.electronics.design Tom Del Rosso <tdne...@att.net.invalid> wrote:
> > N. Thornton wrote:
> >>
> >>> Bad neutral connection in the panel, causing the voltage to swing up?
> >> The UK isnt wired like that, so we dont get that problem.
>
> > We have center tapped transformers, where the center tap is grounded at
> > the source. What do you have? Since you use 220-240V I would guess you
> > don't need a center tap and neither line is grounded.
>
> Usaually delta-star transformers with the neutral point grounded at the
> transformer. 230V from any of the 3 phases to neutral, 400V between
> phases.
I think I've forgotten the few ee/ece courses that I'd taken many
years ago, but from what I remember, I don't get the voltage between
any two phases equal to 400V. I did
the math like follows:
The phase diff between any two phases is 120 degress. So we can draw
a circle and three radii at 120 degrees to each other. The length of
the radii is 230 V. The voltage between any two phases is the length
of the line joining the tips of those two radii. By this math, you
get the length to be equal to 2 * 230/sin(60) = 531.16 V!!
What's wrong here?
-- pankaj
Malcolm Moore
wrote:
>
>I think I've forgotten the few ee/ece courses that I'd taken many
>years ago, but from what I remember, I don't get the voltage between
>any two phases equal to 400V. I did
>the math like follows:
>
>The phase diff between any two phases is 120 degress. So we can draw
>a circle and three radii at 120 degrees to each other. The length of
>the radii is 230 V. The voltage between any two phases is the length
>of the line joining the tips of those two radii. By this math, you
>get the length to be equal to 2 * 230/sin(60) = 531.16 V!!
>
>What's wrong here?
>
>-- pankaj
That should be 2*230*cos(30)= 398.37V
which simplifies to 230*sqrt3
Plot the 3 sine waves against time on the X axis. The 3 waveforms will
be 120 degrees apart.
The voltage between phases can then be easily visualised. When one
phase is at max +ve the other two will be -ve, but less than maximum.
While these are instantaneous values the same applies to the rms.
Your result above gives a figure greater than twice the phase voltage.
To use the phasor diagram you use in your post you don't just take the
distance between two radii, you add the inverted phasor of one to the
phasor of another and the resultant is the potential between them.
Regards
Malcolm.
Tony Williams
Pankajkumar Chauhan <no_...@dev.null> wrote:
> The phase diff between any two phases is 120 degress. So we can
> draw a circle and three radii at 120 degrees to each other. The
> length of the radii is 230 V. The voltage between any two phases
> is the length of the line joining the tips of those two radii.
> By this math, you get the length to be equal to 2 * 230/sin(60) =
> 531.16 V!!
> What's wrong here?
The sin(60) is upside down. It should be 2 * 230*sin(60).
--
Tony Williams.
Malcolm Moore
>
> I think I've forgotten the few ee/ece courses that I'd taken many
> years ago, but from what I remember, I don't get the voltage between
> any two phases equal to 400V. I did
> the math like follows:
>
> The phase diff between any two phases is 120 degress. So we can draw
> a circle and three radii at 120 degrees to each other. The length of
> the radii is 230 V. The voltage between any two phases is the length
> of the line joining the tips of those two radii. By this math, you
> get the length to be equal to 2 * 230/sin(60) = 531.16 V!!
>
> What's wrong here?
>
> -- pankaj
That should be 2*230*cos(30)= 398.37V