Hi,

As I don't have the schematic for the subject monitor, would
anyone familiar with this type of beast be kind enough to point
me in the right direction as this is not my territory.

The fault is that the power-on LED doesn't light and the
monitor will not switch on. My brother, whose monitor this is,
tells me that it died quietly - no theatrics or funny smells.
There is around 300V DC (this is a 240V AC country) on the main
electrolytic in front of the switching converter which appears to
be single ended, showing that the power cord and input fuse are
OK. From the symptoms however, I would guess that there is a low
voltage supply missing.

I expect that the circuit topology is fairly standard but as I
said in the first paragraph, I'm not familiar with them. So if
anybody could roughly map out the likely circuit arrangement for
me and mention any controller chips that are likely to be used, I
would be most grateful.


Cheers - Joe

Just finished repairing 2 of these- Check H.O.T.=BU2522AX.

FBT also had bad internal cap; measured 400 pf. vs. 2800 pf as a new one,
(plus it was bulged on the side).
These were Envision's Model 1770; same FCC ID ( ARSCM7690 )

FBT P/N=79A769-2-A , same as 79A769-2-C

Can Purchase the FBT online he

http://www.google.com/search?sourcei...79A769%2D2%2DC

the usual reason for this mode of failure is an open-circuit high-value
resistor which provides the turn-on voltage to the SMPS controller chip.

Test all the resistors around the PSU area for value.

Most likely the resistor (or could be 2 in series) is a ~100k-470k 1/2w or
1w carbon or metallised type.


Craig


"Joe McElvenney" wrote in message
...
Hi,

As I don't have the schematic for the subject monitor, would
anyone familiar with this type of beast be kind enough to point
me in the right direction as this is not my territory.

The fault is that the power-on LED doesn't light and the
monitor will not switch on. My brother, whose monitor this is,
tells me that it died quietly - no theatrics or funny smells.
There is around 300V DC (this is a 240V AC country) on the main
electrolytic in front of the switching converter which appears to
be single ended, showing that the power cord and input fuse are
OK. From the symptoms however, I would guess that there is a low
voltage supply missing.

I expect that the circuit topology is fairly standard but as I
said in the first paragraph, I'm not familiar with them. So if
anybody could roughly map out the likely circuit arrangement for
me and mention any controller chips that are likely to be used, I
would be most grateful.


Cheers - Joe

Craig,

Thanks for that and I will certainly look out for it once I've
ascertained which controller chip is involved. Meanwhile I've
been able to supply my brother with a spare monitor so the
pressure is off me to get the AOC monitor back in action quickly.

It was just that I haven't worked in that area of electronics
and not having a schematic wasn't sure how standby power was
obtained. Just now however, looking at the manual for my Philips
TV, I see that the input SMPS is used in 'burst mode' while in
standby, which I found quite interesting.


All the best - Joe

Hey, I have one AOC 17". I watching it right now!
I get it for free, some thing was broken.
And yes, fixing a couple of bad soldering and it worked again!

/Nisse

Joe McElvenney wrote:
Hi,

As I don't have the schematic for the subject monitor, would
anyone familiar with this type of beast be kind enough to point
me in the right direction as this is not my territory.

The fault is that the power-on LED doesn't light and the
monitor will not switch on. My brother, whose monitor this is,
tells me that it died quietly - no theatrics or funny smells.
There is around 300V DC (this is a 240V AC country) on the main
electrolytic in front of the switching converter which appears to
be single ended, showing that the power cord and input fuse are
OK. From the symptoms however, I would guess that there is a low
voltage supply missing.

I expect that the circuit topology is fairly standard but as I
said in the first paragraph, I'm not familiar with them. So if
anybody could roughly map out the likely circuit arrangement for
me and mention any controller chips that are likely to be used, I
would be most grateful.


Cheers - Joe