I have a Dell 1907FPVt monitor that often loses its preset settings for
brightness, color, etc. It is not a problem in that I have found a way
around it, but I was wondering if there is a better solution than the
one I found.

The above monitor will come on without pressing the power switch if one
were to simply plug it in to AC. That is simply a characteristic of the
monitor as I discovered through a search for that model. I have the
monitor attached to a UPS along with my computer, so if I remove power
completely by shutting down the UPS, when I power it up the monitor
automatically turns on. It appears that when the monitor powers up in
this way, it sometimes (20% of the time) fails to assume the preset
settings. Once it is powered up, I can set the settings to factory
settings and the monitor responds properly.

Since it appeared to me to be a situation where power had perhaps not
risen fast enough to read the retained settings, I opened up the monitor
looking for a cap that was weak. Using a ESR meter, I found none. I
did not trace out the standby voltage circuit and perhaps I should have,
but I had no schematic and it appeared to be more work than I was
prepared to do.

What I have discovered as I was suspecting, is that the monitor never
loses its settings if the monitor remains plugged in and it is turned
off via the switch on the monitor. So it appears that the standby
voltage is not coming up fast enough.

So my questions are these: Has anyone else experienced a similar
problem? And if so, were you able to solve it? Or am I locked into
keeping the monitor attached to AC so it maintained the standby voltage
and use the switch on the monitor to turn it on? I find the latter
solution awkward as it defeats the purpose of the UPS, and I would need
to change the monitor power cable to one attached to the UPS when a
power interruption occurs.

On 13/02/2014 15:06, Ken wrote:
I have a Dell 1907FPVt monitor that often loses its preset settings for
brightness, color, etc. It is not a problem in that I have found a way
around it, but I was wondering if there is a better solution than the
one I found.

The above monitor will come on without pressing the power switch if one
were to simply plug it in to AC. That is simply a characteristic of the
monitor as I discovered through a search for that model. I have the
monitor attached to a UPS along with my computer, so if I remove power
completely by shutting down the UPS, when I power it up the monitor
automatically turns on. It appears that when the monitor powers up in
this way, it sometimes (20% of the time) fails to assume the preset
settings. Once it is powered up, I can set the settings to factory
settings and the monitor responds properly.

Since it appeared to me to be a situation where power had perhaps not
risen fast enough to read the retained settings, I opened up the monitor
looking for a cap that was weak. Using a ESR meter, I found none. I
did not trace out the standby voltage circuit and perhaps I should have,
but I had no schematic and it appeared to be more work than I was
prepared to do.

What I have discovered as I was suspecting, is that the monitor never
loses its settings if the monitor remains plugged in and it is turned
off via the switch on the monitor. So it appears that the standby
voltage is not coming up fast enough.

So my questions are these: Has anyone else experienced a similar
problem? And if so, were you able to solve it? Or am I locked into
keeping the monitor attached to AC so it maintained the standby voltage
and use the switch on the monitor to turn it on? I find the latter
solution awkward as it defeats the purpose of the UPS, and I would need
to change the monitor power cable to one attached to the UPS when a
power interruption occurs.

ESR does not necessarily find low capicitance caps, try a 1KHz RLC meter
set on C if the circuit allows it

Many times you'll find a small ceramic in parallel with the 'lytic. The ceramic cap will 'fool' the ESR meter. If it reads bad with an ESR meter it is bad. If it reads good you need to remove it, let it cool off (heat improves it ) and measure it again. There's a good chance the cap is bad. In switching supplies the caps need to be perfect. There is no 'good enough'. Make sure you buy caps with lowest E$R / highest ripple current.

G²

Thanks for the replies, I shall look closer at the caps should I open up
the monitor again.