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  #31  
Old March 31st 17, 09:30 PM posted to uk.tech.digital-tv
Indy Jess John
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Posts: 1,045
Default TV socket charge up

On 31/03/2017 20:52, Benderthe.evilrobot wrote:

Battery mains portables almost always had a mains transformer that also
provided isolation.


The one that gave me a mains shock when I switched it on had a dropper
resistor; the HT battery connected to the radio side of the rectifier
(via an either/or switch).

Most mains only sets were live chassis - I assume the ones with a mains
transformer must've been deluxe models, there were much fewer about.


Nearly every mains only set I looked at had a transformer.


Only very early TVs had mains transformers - dropper resistors were much
cheaper and lighter.


I must take your word for that - I never took the back off a TV.

Jim
  #32  
Old March 31st 17, 09:49 PM posted to uk.tech.digital-tv
Max Demian
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Posts: 3,718
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On 31/03/2017 22:30, Indy Jess John wrote:
On 31/03/2017 20:52, Benderthe.evilrobot wrote:

Battery mains portables almost always had a mains transformer that also
provided isolation.


I used to have one that didn't, as it was supposed to work off 100-250V
AC or DC. There was originally a resistive mains lead to drop the
voltage, and mains valves for rectification and power output in addition
to four economy valves designed for battery use.

The one that gave me a mains shock when I switched it on had a dropper
resistor; the HT battery connected to the radio side of the rectifier
(via an either/or switch).

Most mains only sets were live chassis - I assume the ones with a mains
transformer must've been deluxe models, there were much fewer about.


Nearly every mains only set I looked at had a transformer.


I think only the ones intended to be run off DC mains had the chassis
connected to one side of the mains. If intended as AC/DC there would be
a (usually valve) rectifier diode, so if you had DC you might have to
reverse the (2 pin) plug in the socket (or lamp holder) to get it to
work. I suppose that DC mains would have the negative side earthed at
the generator so the chassis wouldn't be too live.

--
Max Demian
  #33  
Old April 1st 17, 01:50 AM posted to uk.tech.digital-tv
Johnny B Good[_2_]
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Posts: 387
Default TV socket charge up

On Fri, 31 Mar 2017 14:39:07 +0100, Bill Wright wrote:

On 31/03/2017 14:29, Johnny B Good wrote:

Most components in a typical telephone handset (instrument) in both
the
Tele 300 and Tele 600 series, along with various switches and selectors
used in Strowger exchanges had two or more functions. For example the
bell capacitor not only provided a path for the 16.67Hz ringing current
to operate the magneto bell, it also formed part of the anti-sidetone
circuit as well as part of the spark quench (snubber) circuit for the
rotary dial impulse interrupter contacts.


blah blah blah erudition knowledge blah blah blah

[1] Minimising "Component Count" by minimising 'redundancy' in the
circuitry of an assemblage such as a telephone instrument or a rotary
selector switching stage in a Strowger exchange was a well established
practice that was old even back then (50 years or older!).


I calculate that you were typing and thinking at 45wpm when you wrote
that. 1,271 words in 28 minutes. Remarkable.


I'm aware that I have a tendency to go a little OTT in many of my posts
(that's why I tend to stay out of many discussion threads when I can see
that any contribution I might make would simply be more a case of "AOL"
than a useful additional contribution). In this case, Huge's quite
sensible matter of fact reply just seemed to be in need of a little
amplification to properly settle the question of the economics of modern
day manufacturing over the best part of the last hundred years.

I presume your final remarks over the apparent wpm speed of my reply are
intended to be taken as praise. I'm not sure how you were able to
calculate that 45wpm figure but, if correct, seems rather speedier than
my usual two page replies which so often, due to real life interruptions,
take several hours to complete on occasion.

I suppose it's just possible that, having got the bit between my teeth
on a subject I've raised before (and therefore well rehearsed in my
mind), I may actually have knocked it out in a mere half hour of pounding
the keyboard (and proof reading - vanity can be such a cruel mistress!).

I just find it a little surprising that I could have produced such a
screed in so little a time as you calculated. In any case, Bill, I thank
you for noticing the remarkably high wpm of my reply and for taking the
time to calculate and inform me of the result. :-)

--
Johnny B Good
  #34  
Old April 1st 17, 08:13 AM posted to uk.tech.digital-tv
Ian Jackson[_7_]
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Posts: 23
Default TV socket charge up

In message , Max
Demian writes
On 31/03/2017 22:30, Indy Jess John wrote:
On 31/03/2017 20:52, Benderthe.evilrobot wrote:

Battery mains portables almost always had a mains transformer that also
provided isolation.


I used to have one that didn't, as it was supposed to work off 100-250V
AC or DC. There was originally a resistive mains lead to drop the
voltage, and mains valves for rectification and power output in
addition to four economy valves designed for battery use.

The one that gave me a mains shock when I switched it on had a dropper
resistor; the HT battery connected to the radio side of the rectifier
(via an either/or switch).

Most mains only sets were live chassis - I assume the ones with a mains
transformer must've been deluxe models, there were much fewer about.


Nearly every mains only set I looked at had a transformer.


I think only the ones intended to be run off DC mains had the chassis
connected to one side of the mains.


I doubt if there were any normal TV sets or radios that were designed
only to run off DC mains.

If intended as AC/DC there would be a (usually valve) rectifier diode,
so if you had DC you might have to reverse the (2 pin) plug in the
socket (or lamp holder) to get it to work.


Can you imagine what might happen if there was no rectifier included as
standard?

I suppose that DC mains would have the negative side earthed at the
generator so the chassis wouldn't be too live.

Yes - with an AC/DC set, the intention is that the user should ensure
that the chassis side is connected to the mains neutral (although this
is rarely earth zero volts).

Unfortunately, with AC mains, the set works just as well with the mains
connected the wrong way round, and the chassis is at mains live voltage
(230V). To prevent killing about half the population, in TV sets the
aerial coaxial connection was via low-value capacitors, and radio sets
with external aerial and earth connections also had both blocked with
capacitors. With both, there was a danger of a user coming into contact
with the grub screws holding the knobs on the metal spindles of the user
controls, so the holes were often filled with wax.
--
Ian
  #35  
Old April 1st 17, 10:41 AM posted to uk.tech.digital-tv
Dave W
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Posts: 232
Default TV socket charge up


"Bill Wright" wrote in message
news
On 31/03/2017 14:29, Johnny B Good wrote:

Most components in a typical telephone handset (instrument) in both the
Tele 300 and Tele 600 series, along with various switches and selectors
used in Strowger exchanges had two or more functions. For example the
bell capacitor not only provided a path for the 16.67Hz ringing current
to operate the magneto bell, it also formed part of the anti-sidetone
circuit as well as part of the spark quench (snubber) circuit for the
rotary dial impulse interrupter contacts.


blah blah blah erudition knowledge blah blah blah

[1] Minimising "Component Count" by minimising 'redundancy' in the
circuitry of an assemblage such as a telephone instrument or a rotary
selector switching stage in a Strowger exchange was a well established
practice that was old even back then (50 years or older!).


I calculate that you were typing and thinking at 45wpm when you wrote
that. 1,271 words in 28 minutes. Remarkable.

Bill


Unusually for me, I actually found it funny this time. Poor bloke must have
had a wiggly bit of plastic fail on him once.
--
Dave W


  #36  
Old April 1st 17, 10:54 AM posted to uk.tech.digital-tv
Max Demian
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Posts: 3,718
Default TV socket charge up

On 31/03/2017 14:29, Johnny B Good wrote:
On Fri, 31 Mar 2017 09:49:07 +0000, Huge wrote:


I expect it was cheaper.


'Twas ever thus. I first met this design paradigm almost half a century
ago[1] when I signed up as a GPO apprentice technician.


Moving on to what might be considered a 'less trivial' example of "Bean
Counteritis", the humble fast boil electric jug kettle, the trick used
here is to deliberately overlook the basic design rule of moulding (and
forging) component parts that are expected to withstand regularly
repeated cycles of dynamic stress such as a con-rod in an ICE or, in this
case, the wishbone shaped plastic lever in the base of the jug kettle by
which the user switches the kettle on or off.


I reckon you could have just been unlucky (or heavy handed). I bought a
plastic jug kettle for £12 from Wilko four years ago - the kind you can
put on the base any way round - and the paddle hasn't broken yet. If it
does I'll have a go at fixing it with Araldite.

--
Max Demian
  #37  
Old April 1st 17, 12:00 PM posted to uk.tech.digital-tv
Paul Ratcliffe
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Posts: 2,424
Default TV socket charge up

On Sat, 01 Apr 2017 01:50:40 GMT, Johnny B Good
wrote:

On Fri, 31 Mar 2017 14:39:07 +0100, Bill Wright wrote:

I calculate that you were typing and thinking at 45wpm when you wrote
that. 1,271 words in 28 minutes. Remarkable.


How long did it take you to count them?

I'm aware that I have a tendency to go a little OTT


Only a little? You're a master of understatement as well it seems.

FWIW, one part of my car's exhaust has just failed 2 years 11 months
and 3 days into its 3 year guarantee.
This also happened on the other part when I last had that replaced.
Seems like the bean counters haven't got it quite right then :-))
  #38  
Old April 1st 17, 01:16 PM posted to uk.tech.digital-tv
Johnny B Good[_2_]
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Posts: 387
Default TV socket charge up

On Sat, 01 Apr 2017 11:41:01 +0100, Dave W wrote:

"Bill Wright" wrote in message
news
On 31/03/2017 14:29, Johnny B Good wrote:

Most components in a typical telephone handset (instrument) in both
the
Tele 300 and Tele 600 series, along with various switches and
selectors used in Strowger exchanges had two or more functions. For
example the bell capacitor not only provided a path for the 16.67Hz
ringing current to operate the magneto bell, it also formed part of
the anti-sidetone circuit as well as part of the spark quench
(snubber) circuit for the rotary dial impulse interrupter contacts.


blah blah blah erudition knowledge blah blah blah

[1] Minimising "Component Count" by minimising 'redundancy' in the
circuitry of an assemblage such as a telephone instrument or a rotary
selector switching stage in a Strowger exchange was a well established
practice that was old even back then (50 years or older!).


I calculate that you were typing and thinking at 45wpm when you wrote
that. 1,271 words in 28 minutes. Remarkable.

Bill


Unusually for me, I actually found it funny this time. Poor bloke must
have had a wiggly bit of plastic fail on him once.


I'm glad you found my missive amusing, Dave. Since I knew that not
everyone in this group would necessarily have an understanding or
appreciation of basic mechanical design rules, "amusing" was a part of
what I was aiming for. :-)

Incidentally, the kettle in question (the previous example of the almost
'classic' fast boil jug kettle) is parked in my basement as an emergency
spare. My repair of the 'wiggly bit of plastic' lasted a couple of years
before the epoxy glue finally softened into a 'set' that caused the
latching action to go out of adjustment, obliging me to 'bend it upward'
every other use.

I was prepared to have another go at fixing it with a better quality
epoxy to supplement the stainless steel wire pins I'd used to join the
broken ends together but the missus insisted on our purchasing another
fast boil jug kettle (and for me to sling "Old Faithful" into the bin).

The replacement kettle is, aside from some minor cosmetic detail,
virtually identical to the previous model so I suspect that once the
basic 12 month warranty expires and I can take it apart with impunity to
examine its inner workings, I'll find a similar, if not identical,
'wishbone lever' designed to fail prematurely using the same abuse of the
design rules normally applied to maximise reliability.

It's a "No Brainer" for the manufacturer to choose such a component as
the mechanism by which to artificially shorten the life cycle of its
product in order to maintain 'repeat business' at a healthy level.

Not only does this result in an undramatic failure, completely devoid of
any newsworthiness (no dramatic bangs and/or flashes), it also has the
charm of being completely devoid of any safety implications as well as
allowing the cheapest remedy in the event of a miscalculation generating
a flood of within warranty returns. Believe me, it's no 'accident' that
this "wiggly bit of plastic" is the main point of failure in the
'classic' fast boil jug kettle.

--
Johnny B Good
  #39  
Old April 1st 17, 01:52 PM posted to uk.tech.digital-tv
Johnny B Good[_2_]
external usenet poster
 
Posts: 387
Default TV socket charge up

On Sat, 01 Apr 2017 11:54:44 +0100, Max Demian wrote:

On 31/03/2017 14:29, Johnny B Good wrote:
On Fri, 31 Mar 2017 09:49:07 +0000, Huge wrote:


I expect it was cheaper.


'Twas ever thus. I first met this design paradigm almost half a
century
ago[1] when I signed up as a GPO apprentice technician.


Moving on to what might be considered a 'less trivial' example of
"Bean
Counteritis", the humble fast boil electric jug kettle, the trick used
here is to deliberately overlook the basic design rule of moulding (and
forging) component parts that are expected to withstand regularly
repeated cycles of dynamic stress such as a con-rod in an ICE or, in
this case, the wishbone shaped plastic lever in the base of the jug
kettle by which the user switches the kettle on or off.


I reckon you could have just been unlucky (or heavy handed). I bought a
plastic jug kettle for £12 from Wilko four years ago - the kind you can
put on the base any way round - and the paddle hasn't broken yet. If it
does I'll have a go at fixing it with Araldite.


You may well be right about the question of "Heavy Handedness", not so
much mine as perhaps that of my youngest offspring. However, since my
natural tendency (by nurture) is towards deep cynicism (I've always taken
a keen scientific interest in the workings of nature and its application
to technology and I believe these two aspects of a man's character,
scientific interest and cynicism, are closely intertwined, one feeding
the other), I immediately spotted the abuses of good design practice
embodied in the very shape of this non-safety issue, cheap function
critical part. :-)

Apropos of any future repair, it'll need a little bit more than just a
dab of high quality high temperature epoxy glue to join the broken ends
of the "wiggly bit of plastic" together. In my case, it was a couple of
12 to 15mm lengths of .5mm or so diameter stainless steel spring wire and
a matching size drill bit to drill the necessary 6 to 8 mm deep holes
into the broken ends of the arms of said "wiggly bit of plastic".

My biggest problem was due to the limited clearance around the join
resulting in the need to keep freeing off the slowly setting blob of
epoxy glue from the adjacent obstructions. If I had planned the job in a
little more detail, I'd have made good use of silicone backed paper
strips to avoid the need to actively prevent unwanted bonding between the
wishbone shaped lever and adjacent structures. You can take note of this
potential problem and hopefully, should the need ever arise, achieve a
successful and trouble free repair. :-)

Alternatively, make good use of a 3D printer, yours or someone else’s -
it doesn't really matter except for the fact that using someone else's is
likely to be the cheapest option, especially if you can find an
enthusiast only too willing to demonstrate the worthiness of their latest
3D printer acquisition (or 'build') for free. :-)

--
Johnny B Good
  #40  
Old April 1st 17, 02:35 PM posted to uk.tech.digital-tv
Indy Jess John
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Posts: 1,045
Default TV socket charge up

On 01/04/2017 13:00, Paul Ratcliffe wrote:

FWIW, one part of my car's exhaust has just failed 2 years 11 months
and 3 days into its 3 year guarantee.


I bought a car, second hand, in 1984. In 1985, the rear silencer rusted
through and I bought a stainless steel replacement. In 1986 the middle
silencer rusted through, and I replaced the rest of the exhaust system
with a stainless steel equivalent. Both stainless steel purchases were
guaranteed "for life" which was defined as indefinitely provided it was
still on the car for which it was purchased while still owned by the
purchaser.

In 2008 the car was declared beyond economic repair by the MOT tester
(it needed an entire new floor), so I scrapped it. It had cost me 500
in 1984 and it had served me well for 24 years, so I couldn't really
complain. The stainless steel exhaust was still fully functional when I
drove it to the scrapyard.

If you are thinking of keeping a car for any length of time, stainless
steel does seem to last well.

Jim
 




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