Re: LCD Monitor Problem - Turns on and off


"Bill Simpson" <plusnetfiles@xxxxxxxxxxxxxxx> wrote in message
news:qids02pd1js4o7rlf6labhan24s755bq92@xxxxxxxxxx

Thanks for all the help. Since you introduced the concerns about
maintaining the proper polarity. Is there a simple way to verify
this? I recently pick up a new Greenlee DM-810 True RMS Digital
Multimeter at a garage sale for $5. Does this have a function that
would test polarity?


Bill, I'm assuming that this is a digital meter - yes ? OK. Making sure that
you have the red probe in the red socket, and the black in the black socket,
then just go ahead and measure the output. If you have your red lead
connected to the positive output wire, then the meter will just
read " 12.00 " or whatever. If you have your red lead connected to the
negative output wire, then the meter will read " - 12.00 " ie a minus sign
at the front of the number.

As additional confirmation, the original power supply may well have a little
picture of the output connector, indicating polarity, as might the monitor
by its input socket. Additionally, as any replacement you buy is likely just
a generic type, it will probably also have a picture of its plug, indicating
polarity. For what it's worth, you very likely will not have to do any
cutting and grafting. In general, there seems to be a loose " standard " on
the plug size and polarity sense, employed by the current crop of externally
powered LCD monitors and TVs. But that said, I emphasise, better to be safe
than sorry ...

Arfa

On Mon, 06 Mar 2006 14:06:46 GMT, "Arfa Daily"
<arfa.daily@xxxxxxxxxxxx> wrote:


"Bill Simpson" <plusnetfiles@xxxxxxxxxxxxxxx> wrote in message
news:aj9o02dm6d2n47hu4qlusena3qnlvf3o1d@xxxxxxxxxx
On Mon, 06 Mar 2006 09:03:42 GMT, "Arfa Daily"
<arfa.daily@xxxxxxxxxxxx> wrote:

I see that my reply did get double posted. Thanks for the very
precise information. With my rather low level of technical knowledge,
do you think it more advisable that I just replace the power supply?

The power supply that I currently have is

Sunny
Input :100-240 - 1.6A Max, 50-60Hz, 70-80VA
Output: +12V - 4.0A

I contacted the manufacturer of the monitor and they want $75 for a
replacement power supply (More on that later). I've found some others,
more reasonably priced online. One is a 12V 5A (60W) and the other is
a 12V 4.16A (50W). Am I correct in assuming that both should work?
If the connector is different in these power supplies, would cutting
and soldering the original connector to the new power supply be
acceptable rather than the more complicated and dangerous course that
professionals with your expertise would take? I know it's a crude
solution, but it's something I would feel comfortable with.

The rest if off topic, but if you have some time, I would like your
opinion. I had mentioned earlier that I contacted the manufacturer
about a new power supply. I went to their home page and read the FAQ
ahead of time. I found this in the FAQ:

"My screen comes on for a second and then goes black. How do I resolve
this issue?

1. Please contact Customer Service for further assistance at
323-346-0888. There is a possible short in the ac adapter. "

It seems that the manufacturer knew about this problem for some time.
I had registered my monitor and asked the representative when I called
why they hadn't notified me of the problem (As the warranty on the
montitor had just run out). I also asked if this wasn't a potential
fire hazard. I got a typical rebuff. My question is: Could a short
in the power supply cause a fire? I this a dangerous situation or
would normal internal safeguards kept anything hazardous from
happening?

Thanks again for all of the expert help. You all went above and
beyond what I expected.


Bill

If you don't feel qualified to go inside the supply, then I would not be
comfortable advising you to do so. The fault almost certainly will be one
of
the things I suggested, but it's not worth risking injury to try to repair
it, if you're not absolutely confident of what you're doing.

Either of the two power supplies should be ok rating-wise. Any power
supply
with a rating of 4 amps, will be a switch mode type, so by very nature
will
be regulated to its declared 12v output.
Cutting and joining on the output lead is fine, BUT make absolutely sure
that you get the polarity the same as original. The monitor will not like
having reverse polarity DC shoved up it ...

If ever I join wires in this way, I always use heatshrink sleeving, which
you could probably get from your local Radio Shack. It shrinks easily with
a
small paint stripper gun on 'low', and does a nice neat job of
re-insulating
the cable, and reinforcing the join.

As far as the manufacturer's statement about a " short in the power supply
"
goes, it's probably a bit of generic techno-babble that means nothing more
than ' a faulty power supply '. Joe public can equate with a " short ". It
sounds just technical enough to be describing something real, but is
basically meaningless in this context. It is unlikely that any fire would
ensue from any of the typical ( and much more likely ) faults that the
power
supply would really be suffering from. It's probably just a typical switch
mode power supply design issue, where whover laid out the board, decided,
as
they always seem to, to place an important cap right next to a resistor
that
gets hot. It probably just happens that the fallout from this has been
particularly bad for this manufacturer, using this ( almost certainly
bought-in ) power supply on his particular product.

Arfa





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