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From: Bill Simpson on 5 Mar 2006 20:30
On Sat, 04 Mar 2006 18:57:30 GMT, "Arfa Daily"
<arfa.daily(a)ntlworld.com> wrote:

What you described is precisely what is happening. What you said
about the boot process being a Red Herring, I believe is correct.
Thanks to the rest of your for your help, apologies for the difficulty
in description.

Do you suggest that I first test the output of the power supply?

Thanks again

>
>"tvguy" <no(a)spam.invalid> wrote in message
>news:1A6Of.198994$H54.155366(a)fe03.news.easynews.com...
>> It don`t sound like a bad inverter if it is running good when plugged
>> directly to the wall outlet. If it only does this when plugged into
>> the powersupply of the computer then this would be a problem of the
>> computers powersupply. Did you try to plug it into another computer
>> to see if you still have the same problem ? I would suggest to try
>> this first and see what happens.
>>
>>
>Maybe I read it wrong, but I don't think that this is what the guy was
>saying. I read it as he was always using the external power unit, that came
>with the LCD monitor, and if he left it plugged in the wall, ie with power
>always available to this power supply, but with the monitor turned off, when
>he came to switch the monitor on, it came on ok. If, however, he plugged in
>to any power source that was turned off for periods of time eg his UPS, or
>unplugged from the wall for any length of time, then when he came to put
>power back on the PSU, and then tried immediately to switch on the monitor,
>he got the buzzing, spitting failure to start up, which is typical of a
>defective switching PSU, with bad electrolytics. Perhaps the OP can confirm
>??
>
>If this is actually the case, then all the stuff about Windows and rebooting
>etc is probably a red herring. It just relates to the length of time all
>this takes, which gives the power supply time to struggle to a startup.
>
>Arfa
>

From: tvguy on 5 Mar 2006 23:02
> Arfa Dailywrote:
"tvguy" <no(a)spam.invalid> wrote in message
> news:1A6Of.198994$H54.155366(a)fe03.news.easynews.com...
> It don`t sound like a bad inverter if it is running good when
plugged
> directly to the wall outlet. If it only does this when plugged into
> the powersupply of the computer then this would be a problem of the
> computers powersupply. Did you try to plug it into another computer
> to see if you still have the same problem ? I would suggest to try
> this first and see what happens.
>
>
> Maybe I read it wrong, but I don't think that this is what the guy
was
saying. I read it as he was always using the external power unit, that
came
with the LCD monitor, and if he left it plugged in the wall, ie with
power
always available to this power supply, but with the monitor turned
off, when
he came to switch the monitor on, it came on ok. If, however, he
plugged in
to any power source that was turned off for periods of time eg his
UPS, or
unplugged from the wall for any length of time, then when he came to
put
power back on the PSU, and then tried immediately to switch on the
monitor,
he got the buzzing, spitting failure to start up, which is typical of
a
defective switching PSU, with bad electrolytics. Perhaps the OP can
confirm
??

If this is actually the case, then all the stuff about Windows and
rebooting
etc is probably a red herring. It just relates to the length of time
all
this takes, which gives the power supply time to struggle to a
startup.

Arfa[/quote:733e2a47e2]

If that was what he was stating. I may have read his post wrong to
what he was trying to say. Then I would have to say yes that he has
something wrong with the external powersupply.

From: Arfa Daily on 6 Mar 2006 04:03

"tvguy" <no(a)spam.invalid> wrote in message
news:TvOOf.7298$Pu3.1234(a)fe12.news.easynews.com...
>> Arfa Dailywrote:
> "tvguy" <no(a)spam.invalid> wrote in message
>> news:1A6Of.198994$H54.155366(a)fe03.news.easynews.com...
>> It don`t sound like a bad inverter if it is running good when
> plugged
>> directly to the wall outlet. If it only does this when plugged into
>> the powersupply of the computer then this would be a problem of the
>> computers powersupply. Did you try to plug it into another computer
>> to see if you still have the same problem ? I would suggest to try
>> this first and see what happens.
>>
>>
>> Maybe I read it wrong, but I don't think that this is what the guy
> was
> saying. I read it as he was always using the external power unit, that
> came
> with the LCD monitor, and if he left it plugged in the wall, ie with
> power
> always available to this power supply, but with the monitor turned
> off, when
> he came to switch the monitor on, it came on ok. If, however, he
> plugged in
> to any power source that was turned off for periods of time eg his
> UPS, or
> unplugged from the wall for any length of time, then when he came to
> put
> power back on the PSU, and then tried immediately to switch on the
> monitor,
> he got the buzzing, spitting failure to start up, which is typical of
> a
> defective switching PSU, with bad electrolytics. Perhaps the OP can
> confirm
> ??
>
> If this is actually the case, then all the stuff about Windows and
> rebooting
> etc is probably a red herring. It just relates to the length of time
> all
> this takes, which gives the power supply time to struggle to a
> startup.
>
> Arfa[/quote:733e2a47e2]
>
> If that was what he was stating. I may have read his post wrong to
> what he was trying to say. Then I would have to say yes that he has
> something wrong with the external powersupply.
>

Yeah, I think that's what he's saying, tvguy - see his additional post
above.

Bill.

I think me and tvguy are now both in agreement. Yes, go for power supply
trouble. I had a FAX machine on my bench last week, which was powered from
an external 24v 1500mA switch mode supply. If left on, it would work for
ever. However, if left unpowered for a few hours, when put back on, the
power supply would struggle for about a minute, to start up.

Once I got inside it, it was fairly obvious that the two series-connected
82k startup resistors were pretty distressed and high. I replaced both these
( they use two in series to double the voltage rating of these small film
resistors ). Also, there was a single 220uF cap on the primary side. When
checked on my ESR meter, this went 38 ohms, which is way, way too high, so
this item was replaced as well. The supply then started up first time, every
time, no matter how long it had been off. Both of the mentioned components
are very common for causing startup trouble in any switcher.

Just a word of warning. If you are not used to switchers, be very very
mindful of your personal safety. This type of supply is VERY dangerous, and
could be lethal. Remember also, that the main smoothing cap will charge to
almost one and a half times your local input voltage. If the supply doesn't
start up, this cap will likely stay charged to very close on this figure for
hours, as most switchers do not employ a leak resistor across it. I would
always recommend having these supplies connected to a bench isolation
transformer, when they are opened to be worked on.

Arfa


From: Bill Simpson on 6 Mar 2006 07:04
On Sat, 04 Mar 2006 18:57:30 GMT, "Arfa Daily"
<arfa.daily(a)ntlworld.com> wrote:

Tried posting this earlier, hope this isn't double posted, problems
again with my ISP. Hope I haven't lost the thread.

What you described is precisely what is happening. What you said
about the boot process being a Red Herring, I believe is correct.
Thanks to the rest of your for your help, apologies for the difficulty
in description.

Do you suggest that I first test the output of the power supply?

Thanks again

>
>"tvguy" <no(a)spam.invalid> wrote in message
>news:1A6Of.198994$H54.155366(a)fe03.news.easynews.com...
>> It don`t sound like a bad inverter if it is running good when plugged
>> directly to the wall outlet. If it only does this when plugged into
>> the powersupply of the computer then this would be a problem of the
>> computers powersupply. Did you try to plug it into another computer
>> to see if you still have the same problem ? I would suggest to try
>> this first and see what happens.
>>
>>
>Maybe I read it wrong, but I don't think that this is what the guy was
>saying. I read it as he was always using the external power unit, that came
>with the LCD monitor, and if he left it plugged in the wall, ie with power
>always available to this power supply, but with the monitor turned off, when
>he came to switch the monitor on, it came on ok. If, however, he plugged in
>to any power source that was turned off for periods of time eg his UPS, or
>unplugged from the wall for any length of time, then when he came to put
>power back on the PSU, and then tried immediately to switch on the monitor,
>he got the buzzing, spitting failure to start up, which is typical of a
>defective switching PSU, with bad electrolytics. Perhaps the OP can confirm
>??
>
>If this is actually the case, then all the stuff about Windows and rebooting
>etc is probably a red herring. It just relates to the length of time all
>this takes, which gives the power supply time to struggle to a startup.
>
>Arfa
>

From: Bill Simpson on 6 Mar 2006 07:41
On Mon, 06 Mar 2006 09:03:42 GMT, "Arfa Daily"
<arfa.daily(a)ntlworld.com> 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.


>
>"tvguy" <no(a)spam.invalid> wrote in message
>news:TvOOf.7298$Pu3.1234(a)fe12.news.easynews.com...
>>> Arfa Dailywrote:
>> "tvguy" <no(a)spam.invalid> wrote in message
>>> news:1A6Of.198994$H54.155366(a)fe03.news.easynews.com...
>>> It don`t sound like a bad inverter if it is running good when
>> plugged
>>> directly to the wall outlet. If it only does this when plugged into
>>> the powersupply of the computer then this would be a problem of the
>>> computers powersupply. Did you try to plug it into another computer
>>> to see if you still have the same problem ? I would suggest to try
>>> this first and see what happens.
>>>
>>>
>>> Maybe I read it wrong, but I don't think that this is what the guy
>> was
>> saying. I read it as he was always using the external power unit, that
>> came
>> with the LCD monitor, and if he left it plugged in the wall, ie with
>> power
>> always available to this power supply, but with the monitor turned
>> off, when
>> he came to switch the monitor on, it came on ok. If, however, he
>> plugged in
>> to any power source that was turned off for periods of time eg his
>> UPS, or
>> unplugged from the wall for any length of time, then when he came to
>> put
>> power back on the PSU, and then tried immediately to switch on the
>> monitor,
>> he got the buzzing, spitting failure to start up, which is typical of
>> a
>> defective switching PSU, with bad electrolytics. Perhaps the OP can
>> confirm
>> ??
>>
>> If this is actually the case, then all the stuff about Windows and
>> rebooting
>> etc is probably a red herring. It just relates to the length of time
>> all
>> this takes, which gives the power supply time to struggle to a
>> startup.
>>
>> Arfa[/quote:733e2a47e2]
>>
>> If that was what he was stating. I may have read his post wrong to
>> what he was trying to say. Then I would have to say yes that he has
>> something wrong with the external powersupply.
>>
>
>Yeah, I think that's what he's saying, tvguy - see his additional post
>above.
>
>Bill.
>
>I think me and tvguy are now both in agreement. Yes, go for power supply
>trouble. I had a FAX machine on my bench last week, which was powered from
>an external 24v 1500mA switch mode supply. If left on, it would work for
>ever. However, if left unpowered for a few hours, when put back on, the
>power supply would struggle for about a minute, to start up.
>
>Once I got inside it, it was fairly obvious that the two series-connected
>82k startup resistors were pretty distressed and high. I replaced both these
>( they use two in series to double the voltage rating of these small film
>resistors ). Also, there was a single 220uF cap on the primary side. When
>checked on my ESR meter, this went 38 ohms, which is way, way too high, so
>this item was replaced as well. The supply then started up first time, every
>time, no matter how long it had been off. Both of the mentioned components
>are very common for causing startup trouble in any switcher.
>
>Just a word of warning. If you are not used to switchers, be very very
>mindful of your personal safety. This type of supply is VERY dangerous, and
>could be lethal. Remember also, that the main smoothing cap will charge to
>almost one and a half times your local input voltage. If the supply doesn't
>start up, this cap will likely stay charged to very close on this figure for
>hours, as most switchers do not employ a leak resistor across it. I would
>always recommend having these supplies connected to a bench isolation
>transformer, when they are opened to be worked on.
>
>Arfa
>

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