How hot should an LCD TV transformer get?
 

Apologies if this is not strictly a digital question. I cannot think of better forum to ask.

I recently bought a cheap and cheerful LCD TV for our camper van. It can run off 12 volt DC or 240
AC, with a supplied transformer. The transformer looks like the type you get with a laptop - a
separate oblong black box.

When working from the mains the transformer gets hot - very hot. Last night we watched 2 hours of
telly and when time came to put it all away I could hardly pick the transformer up. It was almost
too hot to hold.

I am worried about a potential fire risk.
Is this normal? How hot do they normally get?


Thanks - Adam

How hot should an LCD TV transformer get?
 

"Adam Lipscombe" wrote in message
...

Apologies if this is not strictly a digital question. I cannot think
of better forum to ask.

I recently bought a cheap and cheerful LCD TV for our camper van. It
can run off 12 volt DC or 240 AC, with a supplied transformer. The
transformer looks like the type you get with a laptop - a separate
oblong black box.

When working from the mains the transformer gets hot - very hot. Last
night we watched 2 hours of telly and when time came to put it all
away I could hardly pick the transformer up. It was almost too hot to
hold.

I am worried about a potential fire risk.
Is this normal? How hot do they normally get?


Thanks - Adam



Modern PSUs often run warm, sometimes a little too warm, but it should
not run too hot to touch. This suggests either cost cutting on behalf of
the manufacturer or that someone has replaced the PSU with an unsuitable
substitute.

Look at the TV power rating - divide power by volts to get current
requirement, then look at the rating of the PSU. I would personally not
expect the TV to draw more than about 70% or so - tops say 80% of the
PSU rating. If it is higher than that there is no wonder it is getting
hot.

If it appears to be the wrong or an underrated PSU then take it back to
the supplier under the 'unfit for purpose' legislation - remember your
contract is with the supplier not the manufacturer so don't be fobbed
off. On the other hand a call to the manufacturer/importer to see if
they have encountered this problem before may not go amiss.

If all seems OK ratings-wise and you get nowhere with the supply chain
then you may have no option but to replace it at your own cost. Places
such as www.maplin.co.uk will supply you with a switched mode unit that
even as a plug-top may be rated way above that which you already have
and will be considerably lighter to boot.


--
Woody

harrogate three at ntlworld dot com

How hot should an LCD TV transformer get?
 

Yes some are definitely dodgy. I wonder if they are made for a mains voltage
with a lower top limit than ours for some reason.
I've never understood why they allow them to get so hot. After all, all that
heat is power you are paying to use!

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"Woody" wrote in message
...
"Adam Lipscombe" wrote in message
...

Apologies if this is not strictly a digital question. I cannot think of
better forum to ask.

I recently bought a cheap and cheerful LCD TV for our camper van. It can
run off 12 volt DC or 240 AC, with a supplied transformer. The
transformer looks like the type you get with a laptop - a separate oblong
black box.

When working from the mains the transformer gets hot - very hot. Last
night we watched 2 hours of telly and when time came to put it all away I
could hardly pick the transformer up. It was almost too hot to hold.

I am worried about a potential fire risk.
Is this normal? How hot do they normally get?


Thanks - Adam



Modern PSUs often run warm, sometimes a little too warm, but it should not
run too hot to touch. This suggests either cost cutting on behalf of the
manufacturer or that someone has replaced the PSU with an unsuitable
substitute.

Look at the TV power rating - divide power by volts to get current
requirement, then look at the rating of the PSU. I would personally not
expect the TV to draw more than about 70% or so - tops say 80% of the PSU
rating. If it is higher than that there is no wonder it is getting hot.

If it appears to be the wrong or an underrated PSU then take it back to
the supplier under the 'unfit for purpose' legislation - remember your
contract is with the supplier not the manufacturer so don't be fobbed off.
On the other hand a call to the manufacturer/importer to see if they have
encountered this problem before may not go amiss.

If all seems OK ratings-wise and you get nowhere with the supply chain
then you may have no option but to replace it at your own cost. Places
such as www.maplin.co.uk will supply you with a switched mode unit that
even as a plug-top may be rated way above that which you already have and
will be considerably lighter to boot.


--
Woody

harrogate three at ntlworld dot com

How hot should an LCD TV transformer get?
 

....snip...

I've never understood why they allow them to get so hot. After all, all
that heat is power you are paying to use!

YOU are paying for the heat but THEY would have to pay extra to supply a
better transformer!

....snip...

If all seems OK ratings-wise and you get nowhere with the supply chain
then you may have no option but to replace it at your own cost. Places
such as www.maplin.co.uk will supply you with a switched mode unit that
even as a plug-top may be rated way above that which you already have and
will be considerably lighter to boot.

I would be amazed if the supply the OP already has wasn't switched mode.
Once you get past very small power output, a conventional transformer is
huge (relatively). Good comments from the various chain about getting on
more reasonably rated though, if that is the problem. Getting very hot will
also dry out the circuitboard joints etc. and the adapter will have a short
lifespan.

Paul DS.

How hot should an LCD TV transformer get?
 

Brian Gaff wrote:

Yes some are definitely dodgy. I wonder if they are made for a mains voltage
with a lower top limit than ours for some reason.
I've never understood why they allow them to get so hot. After all, all that
heat is power you are paying to use!

Indeed so, but unless low energy is perceived as a selling point,
it will be designed down to a price. Pushing component ratings
to (or beyond) their limits, or using unsophisticated designs,
are both ways of minimising production costs.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

How hot should an LCD TV transformer get?
 

Sorry my mistake. its is indeed a power supply rather than a transformer.

this one cooks...


Cheers - Adam


Chris J Dixon wrote:
Brian Gaff wrote:

Yes some are definitely dodgy. I wonder if they are made for a mains voltage
with a lower top limit than ours for some reason.
I've never understood why they allow them to get so hot. After all, all that
heat is power you are paying to use!

Indeed so, but unless low energy is perceived as a selling point,
it will be designed down to a price. Pushing component ratings
to (or beyond) their limits, or using unsophisticated designs,
are both ways of minimising production costs.

Chris

How hot should an LCD TV transformer get?
 

On Tue, 29 Jul 2008 08:47:04 +0100, Paul D.Smith
wrote:

Getting very hot will also dry out the circuitboard joints etc.

You mean the "circuitboard joints" need to be kept damp? What crap you write.

How hot should an LCD TV transformer get?
 

Paul Ratcliffe wrote:
On Tue, 29 Jul 2008 08:47:04 +0100, Paul D.Smith
wrote:

Getting very hot will also dry out the circuitboard joints etc.

You mean the "circuitboard joints" need to be kept damp? What crap
you write.

Have you never heard of 'dry joints'?

How hot should an LCD TV transformer get?
 

In article , Paul Ratcliffe
scribeth thus
On Tue, 29 Jul 2008 08:47:04 +0100, Paul D.Smith
wrote:

Getting very hot will also dry out the circuitboard joints etc.

You mean the "circuitboard joints" need to be kept damp? What crap you write.

Silly!...

He means preventing "dry joints" caused by high thermal differential
cycles..
--
Tony Sayer

How hot should an LCD TV transformer get?
 

"Adrian" wrote:

Paul Ratcliffe wrote:
On Tue, 29 Jul 2008 08:47:04 +0100, Paul D.Smith

Getting very hot will also dry out the circuitboard joints etc.

You mean the "circuitboard joints" need to be kept damp? What crap
you write.

Have you never heard of 'dry joints'?

Hum. Lets distinguish between the multiple meanings of "dry".

1. If the printed circuit board gets very hot, then the resins in the
PCB substrate tend to lose their more volatile components, making the PCB
brittle, which could be described as "drying out".

2. If the printed circuit board gets very hot, then it will undergo
thermal expansion cycles every time it's switched on and off, with the
solder, copper and substrate expanding at different rates, eventually
creating fatigue fractures, and sometimes pulling the solder away from
the copper and thus invisibly breaking the connection which is known as a
"dry joint".

--
Dave Farrance