I cycled the mains off and back on a few times by means of the RCD, now
a TV doesn't work.

could be a coincidence?
Or do folk tend to unplug stuff?

In article ,
R D S wrote:
I cycled the mains off and back on a few times by means of the RCD, now
a TV doesn't work.

could be a coincidence?
Or do folk tend to unplug stuff?

Depends what you mean by cycle. If I want to reboot my router, I usually
do it via the MCB as that is easier to get at. But leave it off for at
least 10 seconds. The router is on the same radial as the AV setup, and
not had a problem with anything else doing this.

--
*You are validating my inherent mistrust of strangers

Dave Plowman London SW
To e-mail, change noise into sound.

On 10/04/2021 12:10, Dave Plowman (News) wrote:
In article ,
R D S wrote:
I cycled the mains off and back on a few times by means of the RCD, now
a TV doesn't work.

could be a coincidence?
Or do folk tend to unplug stuff?

Depends what you mean by cycle. If I want to reboot my router, I usually
do it via the MCB as that is easier to get at. But leave it off for at
least 10 seconds. The router is on the same radial as the AV setup, and
not had a problem with anything else doing this.


Agreed, there are both high and low tech reasons why you shouldn't cycle
the mains in seconds.

I take it that you've unplugged the TV completely for, say, a minute -
then tried again? Attached boxes, too?

And, yes, it could be a coincidence !

PA

On 10/04/2021 12:10, Dave Plowman (News) wrote:


Depends what you mean by cycle.


The power was turned off and on at the CU numerous times while I was
doing a job.

I've had the back off the TV, there's an IC on the power board with a
crater in it.

In article ,
R D S wrote:
On 10/04/2021 12:10, Dave Plowman (News) wrote:


Depends what you mean by cycle.


The power was turned off and on at the CU numerous times while I was
doing a job.

If off for a reasonable length of time, it shouldn't matter. It was
'cycle' I wondered about. As in switching on and off rapidly.

I've had the back off the TV, there's an IC on the power board with a
crater in it.

When I had a not that old TV PS fail. I bought a used board for it from
Ebay. Given that it's not easy to get schematics these days.

--
*Everyone has a photographic memory. Some don't have film *

Dave Plowman London SW
To e-mail, change noise into sound.

On Sat, 10 Apr 2021 13:58:15 +0100, R D S wrote:

snip

I've had the back off the TV, there's an IC on the power board with a
crater in it.

Ah and that's probably let the magic smoke out. ;-(

The problem from my 'I don't generally like to mess with SMPSU's' POV,
you can't guarantee that it's or it's_just the obvious that's dead.

I did once chase a fault on a PC monitor PSU where it obviously
started with a dry / OC smoothing cap but then escalated to several
other components. Various people had tried repairing them and had
repeatedly replaced an ever growing list of bits (some not 'consumable
cheap') before either hitting the magic component or giving up.

After trying the things that were suggested as the 'most likely' that
didn't work I found a complete new PSU from China that cost less than
even a couple of rounds of the components ... and that worked straight
away. ;-)

I did however replace it's main smoothing cap with the better quality
one I'd bought for the faulty PSU so even less was lost and it might
then last longer.

As an aside, I saw a stack of 5 cars on the back of a scrap lorry the
other day. They all looked undamaged (well, other than where they were
stacked directly on each other) and were all newer than our car and
imagine many may have been written off for the sake of a few pence
worth of components. ;-( [1]

Cheers, T i m

[1] A mate used to repair vehicle 'computers' and very often it was
only a few pence worth of parts that turned them from 'working' to 'a
very costly replacement and diagnostic re-configuring'.

On 10/04/2021 15:08, T i m wrote:
On Sat, 10 Apr 2021 13:58:15 +0100, R D S wrote:

snip

I've had the back off the TV, there's an IC on the power board with a
crater in it.

The problem from my 'I don't generally like to mess with SMPSU's' POV,
you can't guarantee that it's or it's_just the obvious that's dead.

Indeed, and i'm pitiful at soldering.

After trying the things that were suggested as the 'most likely' that
didn't work I found a complete new PSU from China that cost less than
even a couple of rounds of the components ... and that worked straight
away. ;-)

I've found a board for $20 odd overseas but I don't want to be without
it too long so there's a place in the UK you can post them to for
repair/exchange for about £40.

I feel like most would see this as an opportunity to get a new massive
telly!

On Sat, 10 Apr 2021 17:01:32 +0100, R D S wrote:

On 10/04/2021 15:08, T i m wrote:
On Sat, 10 Apr 2021 13:58:15 +0100, R D S wrote:

snip

I've had the back off the TV, there's an IC on the power board with a
crater in it.

The problem from my 'I don't generally like to mess with SMPSU's' POV,
you can't guarantee that it's or it's_just the obvious that's dead.

Indeed, and i'm pitiful at soldering.

Ah, that might not help.

After trying the things that were suggested as the 'most likely' that
didn't work I found a complete new PSU from China that cost less than
even a couple of rounds of the components ... and that worked straight
away. ;-)

I've found a board for $20 odd overseas but I don't want to be without
it too long so there's a place in the UK you can post them to for
repair/exchange for about £40.

I feel like most would see this as an opportunity to get a new massive
telly!

Quite!

A mate bought such, selling me his 40" shuffled-though (his old lounge
TV went into his bedroom, what he sold me came out etc) TV and his new
set looked *massive* (to both of us) but now he doesn't see it as
large at all.

Once you have the new TV you can bide you time re fixing the old one?

Cheers, T i m

On 10/04/2021 13:58, R D S wrote:
On 10/04/2021 12:10, Dave Plowman (News) wrote:


Depends what you mean by cycle.


The power was turned off and on at the CU numerous times while I was
doing a job.

I've had the back off the TV, there's an IC on the power board with a
crater in it.

Oops.


--
Ideas are more powerful than guns. We would not let our enemies have
guns, why should we let them have ideas?

Josef Stalin

Well, that sounds like a switch mode psu to me. Normally though those chips
are protected for mains surges etc as early ones would die if a switch to a
motor was sparking, or in the case of a Samsung fax machine i had a
lightning struck half a mile away!

Brian

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"R D S" wrote in message
...
On 10/04/2021 12:10, Dave Plowman (News) wrote:


Depends what you mean by cycle.


The power was turned off and on at the CU numerous times while I was doing
a job.

I've had the back off the TV, there's an IC on the power board with a
crater in it.

On 10/04/2021 11:40, R D S wrote:
I cycled the mains off and back on a few times by means of the RCD, now
a TV doesn't work.

could be a coincidence?
Or do folk tend to unplug stuff?

nothing on at the moment anyway ...

On Saturday, 10 April 2021 at 11:40:22 UTC+1, R D S wrote:
I cycled the mains off and back on a few times by means of the RCD, now
a TV doesn't work.

could be a coincidence?
Or do folk tend to unplug stuff?

The TV might have been powered up for years and just switched to standby mode
when not in use. Many switching power supplies have a small electrolytic
bootstrap capacitor which is only ever used to help start the power supply. This
could have failed ages ago and this would only have become obvious when the
mains was switched off and on again.

John

R D S wrote:
I cycled the mains off and back on a few times by means of the RCD, now
a TV doesn't work.

could be a coincidence?
Or do folk tend to unplug stuff?


Damage to an inrush limiter on the power front end ?

In this diagram, it is NTCR1 near the plug. NTCR1 tames
the rate that C5/C6 charge up (transient amperes through
the bridge rectifier).

http://www.pavouk.org/hw/en_atxps.html

When an inrush limiter is implemented that way, it
needs time to cool off, between uses. Like, 60 seconds
of power off, then power on again.

Rapidly toggling mains to things like ATX power supplies,
can cause them to pop and fail. in one of the computer
groups, we got a report from someone who had done this
out of frustration, until they heard a "pop" sound
come from the PSU :-)

There is more than one way to implement inrush limiting.
On designs with active PFC, you can use the PFC pass
transistor as an inrush limiter, at powerup. And then there
is no longer a "thermal" issue. The PFC controller recognizes
that T=0 and operates in inrush limiting mode, and then
a fraction of a second later switches to PFC mode.

There is also fuse F1 in that schematic diagram, but because
those are Slo Blow type, they almost never pop. It takes
a proper short circuit in the front end, to open fuse F1.

*******

TV sets are partitioned into "boards", and the power
function is a separate board. You should be able to
recognize the function, by the number of electrolytic
capacitors on the board. The power board has SMPS
(switched mode power supplies), similar to an ATX
supply for a computer, but with different voltages on it.

Power boards are a frequent source of failures, but this
was back during the "capacitor plague" when badly fabricated
capacitors would corrode through and leak. There were some
TVs and computer monitors that suffered for this.

The power boards can be OEM items, and the TV factory
did not necessarily make the power board.

Paul

Yes my edis sub woofer blue up its bridge rectifier a couple of years ago.
When my friend pulled out the offending device and looked it up it was not
rated for peak currents over a certain amount, but when the capacitors were
charged at turn on this current was much higher as a transient, Hence
fitting a more capable bridge slightly raised on wires has been good ever
since. Companies trying to save pennies at the expense of reliability. Now
its giving problems with its switch on, which is supposed to be triggered by
very low levels of audio and kept on for minutes. The only way to boot it up
is to unplug it and plug it in multiple times till it hears the sound.
Suspect some other component is now changing value. Moor cheap crap I
expect.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Paul" wrote in message
...
R D S wrote:
I cycled the mains off and back on a few times by means of the RCD, now a
TV doesn't work.

could be a coincidence?
Or do folk tend to unplug stuff?


Damage to an inrush limiter on the power front end ?

In this diagram, it is NTCR1 near the plug. NTCR1 tames
the rate that C5/C6 charge up (transient amperes through
the bridge rectifier).

http://www.pavouk.org/hw/en_atxps.html

When an inrush limiter is implemented that way, it
needs time to cool off, between uses. Like, 60 seconds
of power off, then power on again.

Rapidly toggling mains to things like ATX power supplies,
can cause them to pop and fail. in one of the computer
groups, we got a report from someone who had done this
out of frustration, until they heard a "pop" sound
come from the PSU :-)

There is more than one way to implement inrush limiting.
On designs with active PFC, you can use the PFC pass
transistor as an inrush limiter, at powerup. And then there
is no longer a "thermal" issue. The PFC controller recognizes
that T=0 and operates in inrush limiting mode, and then
a fraction of a second later switches to PFC mode.

There is also fuse F1 in that schematic diagram, but because
those are Slo Blow type, they almost never pop. It takes
a proper short circuit in the front end, to open fuse F1.

*******

TV sets are partitioned into "boards", and the power
function is a separate board. You should be able to
recognize the function, by the number of electrolytic
capacitors on the board. The power board has SMPS
(switched mode power supplies), similar to an ATX
supply for a computer, but with different voltages on it.

Power boards are a frequent source of failures, but this
was back during the "capacitor plague" when badly fabricated
capacitors would corrode through and leak. There were some
TVs and computer monitors that suffered for this.

The power boards can be OEM items, and the TV factory
did not necessarily make the power board.

Paul

My crystal ball is not working today.


Not normal for this to occur, normally in standby they recover quite well
from unexpected mains failures. However one of mine died between two days,
and it seems to be a psu issue as in standby it looks normal, hit the
remote, it briefly goes green and there is a couple of clicks, then back to
red.
Nobody has managed to fix it as its one of those here today gone tomorrow
makes.
It might be just that you are unlucky and it failed, but might already have
been almost ready to die before hand. If its still under warranty shove it
back otherwise its just what happens, and it really depends on how much you
want to pay to get it fixed Dried out electrolytic are a common cause for
inability to start from standby it seems. I had an old video that needed to
have been warmed with a hair drier before it could run, No idea why.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"R D S" wrote in message
...
I cycled the mains off and back on a few times by means of the RCD, now a
TV doesn't work.

could be a coincidence?
Or do folk tend to unplug stuff?