Acer S231HL LCD LED Monitor - No power

[newbie1]

Hey guys,

Hope you guys are doing well. I need some advise on the below repair. This came as faulty to me.

Model : Acer S231HL LCD LED Monitor
Symptom : No power & No LED light up

Included 19V external power adaptor was measured to be producing correct voltage. Disassembled and saw 2 PCB boards but unsure what are they called. Lol. Pictures attached.

Cross reference to this thread, I am wondering whether the Step Down converter MP1584EN (datasheet) (U705) on this board 715G3603-M02-000-004L is faulty and need to be replaced? Or am I troubleshooting at the wrong section/board of the faulty monitor.

Measurement taken on U705 with respect to Gnd (screw pad of the PCB) with the other board plugged in
Pin 1 (SW) = 0V
Pin 2 (EN) = 2.7V
Pin 3 (COMP) = 2.1V
Pin 4 (FB) = 0V
Pin 5 (GND) = 0V
Pin 6 (FREQ) = 0V
Pin 7 (VIN) = 19V
Pin 8 (BST = 5.2V

There is also no shorting when measuring ohms between all the pins to Gnd (Pin 5) and also between Pins 1 to Pin 7 or Pin 8. As for ZD702 ohms measurement the multimeter shows 1161 ohms between one side and 1 when the probe is reversed. Other zeners and diodes also produced no shorting across their respective legs.

Appreciate your opinions whether I should be zooming in & replace the MP1584EN or other components, which I might overlook, should be checked as well.

Thank you

[retiredcaps]

Re: Acer S231HL LCD LED Monitor - No power

U701/702 and U703/U704 look like two voltage regulators. Measure each and report their readings.

[newbie1]

Re: Acer S231HL LCD LED Monitor - No power

U701/702 and U703/U704 look like two voltage regulators. Measure each and report their readings.

Hey buddy.
Both voltage regulators measured 0v on all 3 legs per regulator. thank you as always.

[retiredcaps]

Re: Acer S231HL LCD LED Monitor - No power

Refer to datasheet and figure 3 and 4. Both give a "typical" application schematic.

1) My guess is that R711 and R727 might be the voltage divider connect to FB.

a) What are the values of R711 and R727?

b) Measure them in circuit and see if they match the markings.

2) SW is connected to a diode, an inductor (L601)??, and capacitor (orange one or C750 backside?).

a) An inductor should read less than 1.0 ohms.

b) See if C750 is shorted.

[budm]

Re: Acer S231HL LCD LED Monitor - No power

Are you getting 19vdc on the two legs of the C109 next to the round inductor on the LED Backlights power supply?

[newbie1]

Re: Acer S231HL LCD LED Monitor - No power

@retired,

1) R711 and R727 are connected to Pin 2 (EN)
a) R711 = ohms keep rising; R727 = 28k ohms
b) unfortunately i could not see any markings on them

2) SW is connected to L701
a) L701 = 0.06 ohms
b) C750 is not shorted

@budm
Did you mean the SMD capacitor C809 on the other board? If yes, then 19V is present across it. FYI, C813 (to the left of inductor L801) is also having 19V across it. thank you

[retiredcaps]

Re: Acer S231HL LCD LED Monitor - No power

@retired,

1) R711 and R727 are connected to Pin 2 (EN)
a) R711 = ohms keep rising; R727 = 28k ohms
b) unfortunately i could not see any markings on them

Everyone has different troubleshooting techniques, but what I'm trying to do is to find the two resistors that are connected to FB and ensure they are not open resistors.

Without the board in front of me, I'm just guessing at resistors that are in close proximity of FB. You should use the continuity feature on your multimeter and find out which 2 resistors are connected to FB.

2) SW is connected to L701

There should be a diode connected to SW. It could be ZD702, but you should use the continuity feature on your multimeter to double check.

If all the components check out, then I would suspect the IC itself is bad?

[retiredcaps]

Re: Acer S231HL LCD LED Monitor - No power

Perhaps email this seller

http://www.ebay.com/itm/321096496166

and see if they will sell you 2 (two) for $5 + free shipping?

[newbie1]

Re: Acer S231HL LCD LED Monitor - No power

Everyone has different troubleshooting techniques, but what I'm trying to do is to find the two resistors that are connected to FB and ensure they are not open resistors.

Without the board in front of me, I'm just guessing at resistors that are in close proximity of FB. You should use the continuity feature on your multimeter and find out which 2 resistors are connected to FB.

There should be a diode connected to SW. It could be ZD702, but you should use the continuity feature on your multimeter to double check.

If all the components check out, then I would suspect the IC itself is bad?

The resistors connected to FB are R713 & R714 and they are not open. Yes, you are right. ZD702 is connected to SW. And it is also not shorted out. I guess, I have no choice but to replace the IC if there are no other input from the rest.

Perhaps email this seller

http://www.ebay.com/itm/321096496166

and see if they will sell you 2 (two) for $5 + free shipping?

Thanks buddy... and thanks for keeping this subforum alive.. .. I can see that the TV section have more views & some people are even posting over there even if their asking about their monitor.. ..
oh wait.. i have a faulty TV here which need some help too.. hehe.. i guess i should be posting there soon.

[retiredcaps]

Re: Acer S231HL LCD LED Monitor - No power

I guess, I have no choice but to replace the IC if there are no other input from the rest.

For a 23 inch LED monitor, I would spend the money to try a new IC assuming the ebay seller is cooperative.

Thanks buddy... and thanks for keeping this subforum alive.. ..

Wrong flag for me.

Unlike the main contributors in the TV forum, I have no hands on with fixing TVs (especially plasmas). I don't have the space, vehicle, time or motivation to find, fix and sell them.

Computer LCDs are smaller and easier to get free.

[newbie1]

Re: Acer S231HL LCD LED Monitor - No power

Replaced the IC. However, in the process badly burnt a track as well and could not figure out where it was 'heading'. I tried to fire it up but is not working.

Eventually, I managed to get hold of a used board, fixed it and the monitor was working fine.
My deepest appreciation and thank you to all who replied in this thread.

[fhyrdemon]

Re: Acer S231HL LCD LED Monitor - No power

I've got the same model monitor and I would like to try to fix mine, but I don't have any experience with electrical work. I've got the same symptoms as the OP has, but I'm not sure if its the monitor or the power cable. I guess my first question would be how to get the thing open xD

[CNXTim]

Re: Acer S231HL LCD LED Monitor - No power

Hi,
i have the same model Acer S231HL now 3 years old. The symptom was a flashing blue LED and the screen flashed but did not fire up - but if left for a while, it eventually decided to behave. Now there is no LED at all. Can someone please let me know how to dismantle the case?
We have an electronics repair shop in town, but since i was once employed as a service technician, pride suggests i should at least try

[crajax]

Re: Acer S231HL LCD LED Monitor - No power

I have this same monitor, I bought in 2010. after a power outage recently it wouldn't power back on. knowing that bad caps are a common problem, and a cheap and easy "try and it see" thing to do, I replaced 3 of the four electrolytic caps on the two boards, as I already had suitable replacements on hand. I re-assembled the monitor, plugged in the monitor and...no difference. still dead.

I ordered some 100v/33uf cap for the one capacitor that I didn't replace, and, a couple weeks later I replaced it, and...voilla, I have a working S231HL monitor.

[ToTheTime]

Re: Acer S231HL LCD LED Monitor - No power

Does anyone have a schematic for the s231HL

[Nightshifter]

Re: Acer S231HL LCD LED Monitor - No power

I have this same monitor, I bought in 2010. after a power outage recently it wouldn't power back on. knowing that bad caps are a common problem, and a cheap and easy "try and it see" thing to do, I replaced 3 of the four electrolytic caps on the two boards, as I already had suitable replacements on hand. I re-assembled the monitor, plugged in the monitor and...no difference. still dead.

I ordered some 100v/33uf cap for the one capacitor that I didn't replace, and, a couple weeks later I replaced it, and...voilla, I have a working S231HL monitor.

Hi Crajax, Do you remember which cap it was that you replaced, the C number and which board?

Thanks

[Nightshifter]

Re: Acer S231HL LCD LED Monitor - No power

Hi Crajax, Do you remember which cap it was that you replaced, the C number and which board?

Thanks

I have now taken my S231HL apart and on those two power/signal input boards I only see four electrolytic caps as listed below:

4.7uF/100v
100uF/50v

470uF/10v
220uF/25v

There is no 33uF/100v. Maybe you meant 3.3uF/100v? If that is so then it's possible that Acer could have upgraded that cap to 4.7uF in their later runs of this monitor.

I'll replace these caps and will post the results if that fixes the problem of no power at the monitor. The power supply brick is lighting up green and indeed putting out 19v as expected.

[Nightshifter]

Re: Acer S231HL LCD LED Monitor - No power

I have now taken my S231HL apart and on those two power/signal input boards I only see four electrolytic caps as listed below:

4.7uF/100v
100uF/50v

470uF/10v
220uF/25v

There is no 33uF/100v. Maybe you meant 3.3uF/100v? If that is so then it's possible that Acer could have upgraded that cap to 4.7uF in their later runs of this monitor.

I'll replace these caps and will post the results if that fixes the problem of no power at the monitor. The power supply brick is lighting up green and indeed putting out 19v as expected.

I have replaced those four caps, two each, on the DC power input/signal input board and monitor functions buttons control board and the monitor is back working fine now. I don't know which cap that was actually bad but better to replace all of them instead of trying to narrow it down to one. They're all the same age so if one is bad, chances are the others will also go sooner or later.

Cheers...