LG monitor PSU? oddity/query

[The Natural Philosopher]

I was curious as to whether the dud "monitor" by some chance needs that
tiny - but within spec - extra bit of juice for no reason.

It is extremely possible. See my earlier post.
In many cases those that like to fix such, go hunting with thermal
cameras and volt and resistance meters to see what component is drawing
,more than it should.
But is it worth all that time and effort to YOU?

Id open it up and look for bulging capacitors, but that is really as far
as I would go.

[Theo]

Picked up a couple of 22EA53T-P monitors from a distress sale.
Experience tells me these things go through PSUs like a sweet tooth in a
sweet factory, so I took 4 pre-used ones just in case.
Of course now one monitor is displayed "failed PSU" symptoms. Flashes
briefly on, then power light goes off. Windows still believes there is a
display there leading to hilarious results.
Swapping for any of the "spare" PSUs produces the same results.
However, the spare PSUs seem to power the other monitor fine. And
swapping it's PSU into the dodgy monitor doesn't fix it.
Before I assume I have 5 "just in the brink" PSUs and an outlier monitor
that takes 1% less power, are there any other things people might suggest.
Loath to buy a *new* PSU and discover these monitors can fail multiple
ways.

I've just fixed (touch wood) a Philips BDM4065UC. I picked up a spare with
a broken panel from ebay and have been swapping bits.

Symptom was the monitor would run fine for maybe half an hour, then there'd
be a loud click and the screen would go off. Turn it off at the mains, turn
it on, screen would come back. But then click and go off after maybe a
minute. Repeat and now it did it after 30 seconds.

I suspected the PSU, so pulled the board. No obvious bulging caps, swapped
it with the spare. Problem still there. Next I pulled the controller board
(with all the HDMI inputs etc). No obvious bulging caps or similar damage.
Swapped it over and that fixed it (thus far)

Given the way the fault recurred more and more often, I suspected something
thermal related. The SoC is under a metal heatsink which is soldered to the
board, and there's not much else on that board. My working theory is that
the thermal paste under there has dried out and so the SoC is overheating.
By swapping it, presumably the replacement has better thermal paste.

It's working now, so I'm not planning on testing this theory out unless I
have to take it apart again, but will do if necessary.

About a decade ago we had a similar fault (display corruption rather than
shutoff) on the ASIC (Altera hardened-FPGA) some Samsung 30" monitors, where
the solution was to drill a lot of ventilation holes above the chip to cool
it better.

So thermals are also something to consider.

Theo

[fred]

Picked up a couple of 22EA53T-P monitors from a distress sale.
Experience tells me these things go through PSUs like a sweet tooth in
a sweet factory, so I took 4 pre-used ones just in case.
Of course now one monitor is displayed "failed PSU" symptoms. Flashes
briefly on, then power light goes off. Windows still believes there is
a display there leading to hilarious results.
Swapping for any of the "spare" PSUs produces the same results.
However, the spare PSUs seem to power the other monitor fine. And
swapping it's PSU into the dodgy monitor doesn't fix it.
Before I assume I have 5 "just in the brink" PSUs and an outlier
monitor that takes 1% less power, are there any other things people
might suggest.
Loath to buy a *new* PSU and discover these monitors can fail multiple
ways.

1. You have a fault that does not disappear on a psu change.

2. The psu powers other known good monitors successfully.

Conclusion: You have a faulty monitor.

[Jethro_uk]

Thanks for the replies all.

Symptoms have now settled down to:

Turn on monitor. There is a brief flash of backlight where you can see
the content, then nada.

PC however still thinks the monitor is there & connected (so you can
hilariously "lose" windows).

Am concurring it's a faulty capacitor on the monitor itself :( Need to
find a way to open the beast and visually inspect. And then rue the say
the local hobbiest shops disappeared as it's £5.00 for a 5p capacitor +
£4.95 P&P :)

[The Natural Philosopher]

Post by Jethro_uk
Thanks for the replies all.
Turn on monitor. There is a brief flash of backlight where you can see
the content, then nada.
PC however still thinks the monitor is there & connected (so you can
hilariously "lose" windows).

Mmm. That suggest that in fact it is simply the backlight PSU that has gone.
Ive got a monitor that has massive hum bars across it like that.
There may well be 3 fluorescent tubes needing a high voltage. And a PSU
that is no longer capable of supplying it.

Likely a chip, a power MOSFET and some caps and inductors

Post by Jethro_uk
Am concurring it's a faulty capacitor on the monitor itself :( Need to
find a way to open the beast and visually inspect. And then rue the say
the local hobbiest shops disappeared as it's £5.00 for a 5p capacitor +
£4.95 P&P :)

Only if you buy from RS etc.
Ebay is the place to go. Loads of people on the dole buying up old stock
from the days when we made stuff, popping it in an envelope and making
50p on the deal.

I've even had stuff from France and Germany cheaper than Farnell or RS

Just don't buy chinese *components* from China. It's all sinclair
radionics shit rebadged rejects.

[Jethro_uk]

Post by The Natural Philosopher

Post by Jethro_uk
Thanks for the replies all.
Turn on monitor. There is a brief flash of backlight where you can see
the content, then nada.
PC however still thinks the monitor is there & connected (so you can
hilariously "lose" windows).

Mmm. That suggest that in fact it is simply the backlight PSU that has gone.
Ive got a monitor that has massive hum bars across it like that.
There may well be 3 fluorescent tubes needing a high voltage. And a PSU
that is no longer capable of supplying it.
Likely a chip, a power MOSFET and some caps and inductors

That is pointing towards junking the monitor :(

Annoying as I like them in pairs. Also - despite it have stuff al value 9
years after manufacture, I can't find one anywhere.

[The Natural Philosopher]

Post by Jethro_uk

Post by The Natural Philosopher

Post by Jethro_uk
Thanks for the replies all.
Turn on monitor. There is a brief flash of backlight where you can see
the content, then nada.
PC however still thinks the monitor is there & connected (so you can
hilariously "lose" windows).

Mmm. That suggest that in fact it is simply the backlight PSU that has gone.
Ive got a monitor that has massive hum bars across it like that.
There may well be 3 fluorescent tubes needing a high voltage. And a PSU
that is no longer capable of supplying it.
Likely a chip, a power MOSFET and some caps and inductors

That is pointing towards junking the monitor :(

It is probably worth opening it up and looking for something obvious
like a bulging 200V electrolytic.

The behaviour suggests its right on the edge of being OK but draws
enough power to shut down the PSU.

Id guess at something on the secondary side of the PSU that feeds the
fluoro tubes. Probably the main smoother cap.

a cursory inspection doesn't find anything obvious, then bin it

Post by Jethro_uk
Annoying as I like them in pairs. Also - despite it have stuff al value 9
years after manufacture, I can't find one anywhere.

Yes. I've got more than a few old monitors that work fine, or have
trivial faults, but are simply *obsolete*.

[Harry Bloomfield Esq]

Post by Jethro_uk
Turn on monitor. There is a brief flash of backlight where you can see
the content, then nada.
PC however still thinks the monitor is there & connected (so you can
hilariously "lose" windows).

That suggests to me, that the backlight has simply failed, rather than
the entire monitor switching off. Can you not see anything on the
screen, despite the lack of backlighting?

[Jethro_uk]

Have prised the back off, and the only suspicious looking thing is an
electrolytic capacitor where there appears to be a slight stretching on
the labelling.

It is cylindrical and marked

30AJ
33
10V

it seems to be on a square plastic mount.

A quick google for the numbers (as usual "lens" is shite) suggests
something like:

https://www.alibaba.com/showroom/smd-electrolytic-
capacitor-33uf-100v.html

Is it really as simple as slide off and on again ?

[Joe]

On Sun, 8 Sep 2024 11:31:18 -0000 (UTC)

Post by Jethro_uk
Have prised the back off, and the only suspicious looking thing is an
electrolytic capacitor where there appears to be a slight stretching
on the labelling.
It is cylindrical and marked
30AJ
33
10V
it seems to be on a square plastic mount.
A quick google for the numbers (as usual "lens" is shite) suggests
https://www.alibaba.com/showroom/smd-electrolytic-
capacitor-33uf-100v.html

Genuine Rubycons are of excellent quality, who knows about Chinese? I'd
pay a bit extra and get the real thing from Farnell or the like,
Panasonic are also top quality.

Post by Jethro_uk
Is it really as simple as slide off and on again ?

Look at the condition of the two terminals. A sure sign of leakage is
one (-ve) or both looking dull or crusted with white stuff. Look around
the device. The lacquered PCB tracks should look a uniform colour,
usually green. When you unsolder the terminals, check for a fishy
smell. No, I'm not joking, the electrolyte seems to have an amine or
similar in it. If the terminals are heavily crusted, it may be
difficult to get enough heat to the remaining solder. Pull the top edge
of the capacitor sideways as you melt the solder until it lifts a bit,
then do the other side, then back and forth. Pulling too hard in one go
is likely to lift the track as the heat will have softened the glue.

Once the old one is off, clean the board with water, dry and do the
usual flux cleaning with a solvent. Make sure everything looks shiny.
If any of the PCB lacquer looks darker than the rest, it will probably
prise off easily and have some electrolyte underneath. The track will
be blackened a bit, make sure it has not been significantly eaten away,
the electrolyte dissolves copper.

[The Natural Philosopher]

Post by Joe
When you unsolder the terminals

How?

Its an SMD.

[Joe]

On Sun, 8 Sep 2024 14:26:56 +0100

Post by The Natural Philosopher

Post by Joe
When you unsolder the terminals

How?
Its an SMD.

But the little stubs of wire under the capacitor stick out a millimetre
or so each side. As long as you don't mind melting the plastic base,
there's more than enough to get an iron tip on, and the PCB pad extends
beyond the terminal all round.

[The Natural Philosopher]

Post by Joe
On Sun, 8 Sep 2024 14:26:56 +0100

Post by The Natural Philosopher

Post by Joe
When you unsolder the terminals

How?
Its an SMD.

But the little stubs of wire under the capacitor stick out a millimetre
or so each side. As long as you don't mind melting the plastic base,
there's more than enough to get an iron tip on, and the PCB pad extends
beyond the terminal all round.

If that is the case, then yes, its possible

[The Natural Philosopher]

Post by Jethro_uk
Have prised the back off, and the only suspicious looking thing is an
electrolytic capacitor where there appears to be a slight stretching on
the labelling.
It is cylindrical and marked
30AJ
33
10V
it seems to be on a square plastic mount.
A quick google for the numbers (as usual "lens" is shite) suggests
https://www.alibaba.com/showroom/smd-electrolytic-
capacitor-33uf-100v.html
Is it really as simple as slide off and on again ?

Sadly no. That is an SMD (surface mount device) that needs a specialised
hot air gun, flux and experience to solder its hidden pads to the pads
on the circuit board.
But you don't have to use SMD. If you pull apart with cutters you should
be able to get to its pads with a soldering iron and remove the wreckage
that way, and solder a device with actual wires coming out to the pads
instead

https://www.ebay.co.uk/itm/394378800788

I am assuming it IS 100v?
If it is it makes perfect sense to be the culprit in this case.

On the other hand, most high street smart phone repair shops would have
the skill and kit to do the repair, if you sourced the correct component
for them

[Joe]

On Sun, 8 Sep 2024 14:26:10 +0100

Post by The Natural Philosopher

Post by Jethro_uk
Have prised the back off, and the only suspicious looking thing is
an electrolytic capacitor where there appears to be a slight
stretching on the labelling.
It is cylindrical and marked
30AJ
33
10V
it seems to be on a square plastic mount.
A quick google for the numbers (as usual "lens" is shite) suggests
https://www.alibaba.com/showroom/smd-electrolytic-
capacitor-33uf-100v.html
Is it really as simple as slide off and on again ?

Sadly no. That is an SMD (surface mount device) that needs a
specialised hot air gun, flux and experience to solder its hidden
pads to the pads on the circuit board.

Not really. You need a temperature-controlled iron with a fairly slim
tip. The problem with hot air in this situation is that the corrosion
on the pads of most of the capacitors meant the PCB had to be
practically melted to get enough heat to the remaining solder.
Resistors nearby would be unsoldered and blown away by the air flow. As
it was, it was sometimes necessary to scrape the terminals back to bare
metal and actually add some more solder to get good enough heat
conductivity to melt the rest.

I used either a 48W Weller or later, my own Chinese 60W iron, and I
changed literally thousands of these things. A couple of cameras, one
broadcast and the other professional, had over a hundred of the wretched
things in each unit, and once one or two had been found to fail, it
wasn't worth just changing them, the whole lot needed to go or there
would soon be more problems.