HP 2311F Monitor: Flashing on & off

[gagaguu]

My HP 2311F monitor is having an issue, turning on and off, after a while. After searching through this forum, I found similar thread (#56) posted by "matt230" on May 2nd 2013. It was suspected bad caps.
Referring to "Bud Martin's guide", I was unable to figure out which caps are not working. The caps look fine by visual (neither bulging nor leaking) but I do not own the capacitance or ESR meter. It would be grateful to have some suggestions which caps might fail.

Followings are the info that I'm able to dig from the monitor:
PSU board: Lelon caps (www.lelon.com.tw)
1) 470uF 25V
2) 330uF 25V
3) 33uF 160V
4) 330uF 16V
Logic board: Su'scon caps (www.su-scon.com)
1) 3 x 100uF 16V
2) 8x 10uF 16V
3) 1 x 2.2uF 50V
Display by LG (LM230WF5)
and the photos which might be useful

Thanks, in advance, for your time.

Regards,
Win K. Soe

[1supertech]

Re: HP 2311F Monitor: Flashing on & off

Check your power supply make sure your getting 12volts. Replace all the caps

[gagaguu]

Re: HP 2311F Monitor: Flashing on & off

i've checked the supply. the display acts normal in the first two or three minutes. i starts turning on and off after that.

[Porto]

Re: HP 2311F Monitor: Flashing on & off

something is getting too hot after two minutes and shuts down, than cools off and restarts etc etc.

Monitor the temperature of the mosfet, I can't read what's written on it but it's that 3 legged thing in the middle of the powerboard.
Also that eight legged IC left of it, I guess that's the driver.

The caps are suspicious also. If they are not bulged or leaking, check the ESR if you are able to.

Bad/cold solder joints?

[gagaguu]

Re: HP 2311F Monitor: Flashing on & off

Hi Porto,
the mosfet (Q855) is B70N08 and IC (I801) is FP6180 from feeling technology.
data sheets are attached.
i'll check the caps solder joints thoroughly again.
thanks for your time and advice.
rgds.

[Porto]

Re: HP 2311F Monitor: Flashing on & off

Then I guess the Fp6180 IC is not the driver for the mosfet.

I had an Acer monitor which had the same problem, worked for a few minutes and then it began to reset again and again...

I wanted to replace the mosfet because I thought that thing was getting too hot because of internal issues; maybe it was already dying on me. Unfortunately, I didn't get the change because I blew not only the mosfet but a few other components also when trying to measure the Gate pin, slipped with the probe, ended up in between the gate and the drain pin, some fireworks and am still waiting for the postman to deliver new components to me!

So, in short, try to desolder that mosfet and (temporary) install a similar other one. If you can't get hold of a SMD mosfet, just try to attach a through hole one just for testing, if the monitor works you know what to order (or leave the through hole if it fits nice).

E.g. an (ST)P50NF60 will do just fine and is quite common, I always use them to test a suspicious mosfet. Pin 1,2 and 3 are similar --> Gate, Drain, Source.

[gagaguu]

Re: HP 2311F Monitor: Flashing on & off

Hi Porto,
noted. will follow up after i come back. so far, stuck in indonesia for a while..
don't wish to have firework though...
thanks for the advise...
rgds.

[budm]

Re: HP 2311F Monitor: Flashing on & off

Try lowing the backlights down to about 50% to see if it will stay on longer.

[gagaguu]

Re: HP 2311F Monitor: Flashing on & off

Hi Budm & Porto,
Appreciate the advices...I'm back at home today and will continue finding the fault...My friends discourage me about trying to get it right..but they don't know that it's not about $$$ but the knowledge, the satisfaction and, ofcourse not omitting, the personal achievement. Again, thank you so much for the advices and your time. I will keep you posted...
Rgds,

[Agent24]

Re: HP 2311F Monitor: Flashing on & off

It looks like this monitor uses an external power supply? Have you checked that for bad capacitors?

[gagaguu]

Re: HP 2311F Monitor: Flashing on & off

Budm,
lowering the backlights doesn't change....solder joints are good enough...is it possible that 6180 converter is dying?...i mean thermal shutdown function in works? coz it's normal in the first 2 or 3 minutes and then blinking starts..."porto" recommend replacing the mosfet...should I start with Lelon caps first?

Agent24,
yes..ext PS...but i may never know bad caps cos i don't have ESR meter (n referring to "budm", checking with capacitance meter is not 100% reliable)...

[Agent24]

Re: HP 2311F Monitor: Flashing on & off

Agent24,
yes..ext PS...but i may never know bad caps cos i don't have ESR meter (n referring to "budm", checking with capacitance meter is not 100% reliable)...

You did not show a photo of the inside of the external PSU so I thought perhaps you had not done even a visual inspection of the capacitors there.

[gagaguu]

Re: HP 2311F Monitor: Flashing on & off

Agent24,
Thanks for the advice...but ext psu is supplying 12V it's supposed to...and the monitor is acting normal in first two to three minutes...
rgds,

[Agent24]

Re: HP 2311F Monitor: Flashing on & off

Got any freezer spray? That could help narrow it down.

I just remembered a monitor I had which had a similar problem. Would start up, work OK for a while, but after the microcontroller IC heated up, it went nuts. I found that if I cooled that IC it would start working again.

[gagaguu]

Re: HP 2311F Monitor: Flashing on & off

Got any freezer spray? That could help narrow it down.

I just remembered a monitor I had which had a similar problem. Would start up, work OK for a while, but after the microcontroller IC heated up, it went nuts. I found that if I cooled that IC it would start working again.

Negative...i could try thin Al heatsink with Cooler Master paste...but IC packaging would not affect that much on heat transfer rate...any advice?

[Agent24]

Re: HP 2311F Monitor: Flashing on & off

Get some freezer spray, or a can of compressed air that can be turned upside down and used as one.

Or try the ideas the others suggested first.

[gagaguu]

Re: HP 2311F Monitor: Flashing on & off

thanks...ribbon cable was gone from wear & tear...will update..

[gagaguu]

Re: HP 2311F Monitor: Flashing on & off : Culprit found but need some advices

Hi all,
I am trying to figure out what's causing my HP 2311F display flicker.
I got really helpful suggestions and advices...
i was following 'BudM's sticky' and it is really an eye opener...
(thank you so much.)
in a nutshell, my monitor was having a LDO regulator, U1 on Logic board, faulty.
For those having same problem as me, you would have a rough idea...
Please refer to the attached datasheet.
(it was thermal shutdown function in action.)
That being said,, what would be the compatible regulator?
Pls help.

regards,
Win K. Soe

[Agent24]

Re: HP 2311F Monitor: Flashing on & off

There are probably several regulators which would do the job.

Go to Digikey\Mouser\Farnell etc and search for one that meets the same specifications.

You need same package type (well, you can get creative but it's easier if you have the same package)
Same output voltage, same output current (1.2A) etc.
Same or lower dropout voltage (NOTE: it's different for different output voltages)

Also, are you sure the regulator is bad, and there's no short on the output?

[gagaguu]

Re: HP 2311F Monitor: Flashing on & off

I borrowed an IR thermometer and checked every converters, regulators, etc...
it checked out this regulator. It's temp is higher than others.
(but the temp is within it's op temp and i dont understand why)
So i tried the dummy test. put a little thermal paste and Al heatsink.
I tested it the day before yesterday for 4 hours plus. ok..
In fact, i m testing it with that heatsink now..it's over 3 hrs and no flicker...
(during this 3 hrs, i took out the heatsink and it flickers, putting it back, ok..)
so I'm 85% sure that regulator is causing the flicker.
From datasheet, it's AX6630A 3.3V.
I will check with RS Singapore.
thank you so much Agent24.