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  #41  
Old April 1st 17, 07:18 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
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Posts: 148
Default TV socket charge up


"Ian Jackson" wrote in message
...
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?


There will always be a rectifier - if there's a mains transformer; the
rectifier will be on the secondary side.

The one's with dropper resistors also have a rectifier so AC operation is
possible. The ones with a transformer let the magic smoke out if you connect
them to DC.


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  #42  
Old April 1st 17, 08:15 PM posted to uk.tech.digital-tv
Ian Jackson[_7_]
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Posts: 23
Default TV socket charge up

In message , Benderthe.evilrobot
writes

"Ian Jackson" wrote in message
...
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?


There will always be a rectifier - if there's a mains transformer; the
rectifier will be on the secondary side.

The one's with dropper resistors also have a rectifier so AC operation
is possible. The ones with a transformer let the magic smoke out if you
connect them to DC.


The old-fashioned things that were intended to work on AC/DC didn't have
(couldn't have) a mains transformer.


--
Ian
  #43  
Old April 1st 17, 08:36 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
external usenet poster
 
Posts: 148
Default TV socket charge up


"Ian Jackson" wrote in message
...
In message , Benderthe.evilrobot
writes

"Ian Jackson" wrote in message
...
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?


There will always be a rectifier - if there's a mains transformer; the
rectifier will be on the secondary side.

The one's with dropper resistors also have a rectifier so AC operation is
possible. The ones with a transformer let the magic smoke out if you
connect them to DC.


The old-fashioned things that were intended to work on AC/DC didn't have
(couldn't have) a mains transformer.


"The ones with a transformer let the magic smoke out if you
connect them to DC." might've been a
clue....................................



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  #44  
Old April 2nd 17, 09:31 AM posted to uk.tech.digital-tv
Roderick Stewart[_3_]
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Posts: 2,003
Default TV socket charge up

On Sat, 1 Apr 2017 21:15:17 +0100, Ian Jackson
wrote:

The old-fashioned things that were intended to work on AC/DC didn't have
(couldn't have) a mains transformer.


Calling a piece of equipment "AC/DC" was just a sneaky way of making a
deficiency into a feature. It's not engineering, it's marketing.

Rod.

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  #45  
Old April 2nd 17, 10:54 AM posted to uk.tech.digital-tv
Max Demian
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Posts: 3,720
Default TV socket charge up

On 02/04/2017 10:31, Roderick Stewart wrote:
On Sat, 1 Apr 2017 21:15:17 +0100, Ian Jackson
wrote:

The old-fashioned things that were intended to work on AC/DC didn't have
(couldn't have) a mains transformer.


Calling a piece of equipment "AC/DC" was just a sneaky way of making a
deficiency into a feature. It's not engineering, it's marketing.


That might apply to valve TVs which lacked a mains transformer for
economy reasons; but were they actually capable of running on DC mains,
which I would have thought didn't exist in the heyday of CRT TVs?

AC/DC radios were certainly made when DC mains existed (1920s and 1930s).

I don't recall TVs /advertised/ as AC/DC. The Cossor 918, discussed here
some time ago, came out in 1950 and had a mains transformer - auto for
HT (so with a potentially live chassis), and with various secondary
windings for valve and CRT heaters. (I downloaded a manual/article PDF
describing it in detail.)

(Confusingly, the term AC/DC was (and maybe still is) used to describe
radios and radio/cassette recorders which will work off AC mains or
internal batteries.)

--
Max Demian
  #46  
Old April 2nd 17, 05:46 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
external usenet poster
 
Posts: 148
Default TV socket charge up


"Roderick Stewart" wrote in message
...
On Sat, 1 Apr 2017 21:15:17 +0100, Ian Jackson
wrote:

The old-fashioned things that were intended to work on AC/DC didn't have
(couldn't have) a mains transformer.


Calling a piece of equipment "AC/DC" was just a sneaky way of making a
deficiency into a feature. It's not engineering, it's marketing.


UK mains were only brought up to any kind of standardisation just in time
for the national grid - prior to that it was a mixed bag od AC and DC areas,
and AC could be anywhere fom 25 - 100Hz depending where you were. The
ability to work on most of the supplies then available was hardly a
deficiency.

Being lighter and cheaper to make almost certainly prolonged it long after
DC supplies had been replaced though.

Early TVs were AC only - the mains transformer was the only way to get EHT
until they perfected the flyback system.


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  #47  
Old April 2nd 17, 05:53 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
external usenet poster
 
Posts: 148
Default TV socket charge up


"Max Demian" wrote in message
o.uk...
On 02/04/2017 10:31, Roderick Stewart wrote:
On Sat, 1 Apr 2017 21:15:17 +0100, Ian Jackson
wrote:

The old-fashioned things that were intended to work on AC/DC didn't have
(couldn't have) a mains transformer.


Calling a piece of equipment "AC/DC" was just a sneaky way of making a
deficiency into a feature. It's not engineering, it's marketing.


That might apply to valve TVs which lacked a mains transformer for economy
reasons; but were they actually capable of running on DC mains, which I
would have thought didn't exist in the heyday of CRT TVs?


DC mains wasn't completely eradicated until putting up the pylons was well
underway.

The earliest TVs were AC only because the transformer was the only way of
getting EHT.


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  #49  
Old April 2nd 17, 07:20 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 1,676
Default TV socket charge up

On 02/04/2017 18:46, Benderthe.evilrobot wrote:

Early TVs were AC only - the mains transformer was the only way to get
EHT until they perfected the flyback system.


What about vibrators?

Bill

 




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