No power on a Acer AL1916

[PlainBill]

Re: No power on a Acer AL1916

Okay, I measured the part and it is 3mm so I will order the $0.58 one (SOT23-3). Could you tell me which caps are for the 5v so maybe I can order caps and diodes but replace the caps first to make sure?

On second look they're 2mm apart, maybe I'll just order both and save shipping...

Wow!! I never noticed that before. Look at the picture of the caps. It looks like those two may be bulging at the top.

I'm not good at recognizing cap brands unless I read the label. And these are positioned so the brand's not readable. What brand are they? If they are on the 'crap brand' list they should be replaced.

Anyway, here is a list of the caps by location.

5V supply
1000 uF @ 16V C924
470 uF @ 16V C926

12V supply
1000 uF @ 25V C923, C931 (yes, two of them)
470 uF @ 25V C925

SMPS supply
100 uF @ 25V C906
47 uF @ 25V C909

Inverter
470 uF @ 25V C203

PlainBill

[RobertoIsRad]

Re: No power on a Acer AL1916

Okay, I measured the part and it is 3mm so I will order the $0.58 one (SOT23-3). Could you tell me which caps are for the 5v so maybe I can order caps and diodes but replace the caps first to make sure?

On second look they're 2mm apart, maybe I'll just order both and save shipping...

[PlainBill]

Re: No power on a Acer AL1916

Finally, results! I tested using the second method and immediately after shorting the pins with a screw driver the led turned on, the screen didn't but at least it's a start. This happened with both monitors!
It might be a small part but I think I may be able to solder a new one in if you believe this to be the defect. I searched for MAX810M on digikey but there were more characters after the "m". I was going to order this part number MAX810MTRGOSCT-ND. Is That correct? Thank you so much

Bear with me for a minute, please. I had one thought last night about this problem. Have you tried replacing any caps in the power supply? If the caps in the 5 Volt supply have not been replaced ther is a small chance that the ultimate cause of the problem is excessive ripple resetting the reset controller. I don't think that is the problem, but want you to be aware of the possibility (I'd rate the chances as less than 10%).

As far as the proper number, I don't know, and haven't been able to find out. The MAX810M is the right polarity and output for this application. The other variable is package. The MAX810M is available in two packages, the SOT23-3 and the SC70-3. It's important to get the right one because the lead spacing is different on the two packages. SOT23-3 is 3 mm long, sc70-3 is 2 mm long.

PlainBill

[RobertoIsRad]

Re: No power on a Acer AL1916

Finally, results! I tested using the second method and immediately after shorting the pins with a screw driver the led turned on, the screen didn't but at least it's a start. This happened with both monitors!
It might be a small part but I think I may be able to solder a new one in if you believe this to be the defect. I searched for MAX810M on digikey but there were more characters after the "m". I was going to order this part number MAX810MTRGOSCT-ND. Is That correct? Thank you so much

[PlainBill]

Re: No power on a Acer AL1916

Sadly I don't have access to either of those tools. If you can give me the name of the part I should order I'm willing to try to solder it in (monitors were free, nothing would be lost if I was unable to do it). I'd be willing to "force it" but then again I bet thats why you wanted the supply...

Not exactly, but close. The reset controller holds the controller in a reset condition until 140 msec after the 5 volt supply rises to 4.38 volts. With a variable 5 volt supply you could monitor the output of the controller. You should see a sudden transition on the output as the input voltage crosses through 4.4 volts.

After some cogitation, I see two ways you can test this. One requires a bit more work, but is unlikely to result in damage to any component or to you. The second could fry the reset controller, but is unlikely to damage you if you are very careful.

First way: This will require two D cells (flashlight batteries), lengths of wires of two different colors and either a holder or some method of holding the batteries in series AND one wire on each end. The result is a 3 volt DC power supply. Connect the positive wire to the top lead of U702 (that's the large 'transistor' just to the left of U406, the reset controller). Connect the negative wire to the bottom lead of U702. Now check the voltage at the upper pin of U406, then the lower right pin of U406. Then disconnect the battery. The upper pin should have been at about 3 volts.

If the voltage on the lower pin of U406 was less than .5 volt, it was holding the reset line low, and the reset controller is working properly. If it was slightly lower that the upper pin, the reset controller is not working properly. If I read the datasheet properly, it should follow the input voltage until it exceeds 4.4 volts, then dropped to less than .5 volts.

The other method of testing requires you reassemble the boards to the LCD panel and hook up all the leads. It also involves working on the monitor with AC power hooked up, so be careful. Locate a screwdriver just wide enough to span the two bottom leads of U406. Position the monitor so you can reach the power button. (This may be easier if you have a helper). Now plug in the AC power, short the two bottom leads of U406 together, then push the power button several times at 1-2 second intervals. If the monitor comes on (or even if the power button lights up), the reset controller is bad. If you smell something like burning plastic, the magic smoke got let out of something. If you smell something like burning flesh, well I warned you to be careful.

The part you are looking for is an ASM810MEURF-T. Equivalent parts should be a MAX810M. Make sure you get the right size part. One is 1.15 mm wide, the other is 1.5 mm.

PlainBill

[RobertoIsRad]

Re: No power on a Acer AL1916

Sadly I don't have access to either of those tools. If you can give me the name of the part I should order I'm willing to try to solder it in (monitors were free, nothing would be lost if I was unable to do it). I'd be willing to "force it" but then again I bet thats why you wanted the supply...

[PlainBill]

Re: No power on a Acer AL1916

Board #1
Left - 0.00
Middle - 4.99
Right - 4.36

Board #2 (fried)
Left - 0.00
Middle - 5.00
Right - 4.24

Thanks again!

Hold the phone!!! I'm going to have to do some research, but you may have identified the problem.

Awww, crap. This is a knock-of of a Maxim IC, the MAX810. Unfortunately, the letters after the digits seem to be significant, and I can't find the datasheet for this vendor.

The quick explanation: This IC holds the TSUM16AK-LF in reset until the power supply is stable. Then it switches, allowing the TSUM16AK-LF to begin processing. But the information is contradictory. The schematic shows the output is low to reset the processor, but the Maxim data sheet says it is high to reset. If it IS 'high to reset', the TSUM16AK-LF is still waiting for 'permission' to start. And since it's got a push-pull output, I don't dare have you force it, do I?

By any chance do you have access to a variable DC supply? Or to someone with a dual trace scope? The IC is available from Digikey, and at $.58 each it's a cheap fix. But you might have noticed it's rather small....

PlainBill

[RobertoIsRad]

Re: No power on a Acer AL1916

Board #1
Left - 0.00
Middle - 4.99
Right - 4.36

Board #2 (fried)
Left - 0.00
Middle - 5.00
Right - 4.24

Thanks again!

[PlainBill]

Re: No power on a Acer AL1916

I discovered there are only so many hours a day that one can sleep. At some point the mind starts running around in circles and I have to do SOMETHING. (Emptying a box of Kleenex every two hours does not qualify as something). As far as recovery, I have COPD. If I can prevent this from settling into my lungs, I will be fine. Unfortunately, somewhere in the design process of the human body a decision was made that the sinuses (sini?) should drain into the lungs. Perhaps the fact that sitting hunched over a keyboard transfers the drainage to the nose IS a sign of intelligent design.

I'm basing these comments on the manual for the Acer AL1916v manual. Chapter 4 is a series of troubleshooting trees. Page 31 covers 'No Power'. Notice the third block down "Measure U701 Pin2=3.3V, U702 Pin2=3.3V". Looking at the excellent picture you provided I note that U701 is not present. The schematic seems to indicate U701 and U702 are alternate components. And your test verifies 3.3 volts is present at U702, pin 2.

Now we have a problem. The next step is "X401 oscillate waveforms are normal". X401 is the crystal oscillator, an oval metal can below and to the right of U702. Checking this requires an oscilloscope.

If that is good, the next step is to replace U401, which provides it's own set of complications. This site indicates they have the part in stock, at a cost of $10. However, replacing this requires advanced reworking skills and some special equipment.

I would suggest you see if you can find a hobbyist or professional in your area who has an oscilloscope and can check the crystal.

EDIT: Before doing that, check the voltages at all three pins of U406 - the discolored component I circled.

PlainBill

[PlainBill]

Re: No power on a Acer AL1916

Thank you so much for your help. I really appreciate it!

Sorry, I'm going to be out of it for at least a couple of days. Nasty head cold.

PlainBill

[RobertoIsRad]

Re: No power on a Acer AL1916

Thank you so much for your help. I really appreciate it!

[PlainBill]

Re: No power on a Acer AL1916

Board #1
Black on left pin:
Middle - .914
Right - The numbers rise until 1.0 and then stop
Black on middle pin:
Left - .153
Right - 1.858
Black on right pin:
Left - .743
Middle - .726

Board #2 The one that looks fried
Black on left pin:
Middle - .548
Right - 1.103
Black on middle pin:
Left - .147
Right - .750
Black on right pin:
Left - .719
Middle - .658

I found a service manual for a AL1916v I think my model is an A (I can't find that one though...). At the end of the manual there are diagrams. I wonder if this would help with finding correct readings, unfortunately I don't really know what any of it means...

I downloaded it and had a quick look at it. Yes, that may help. Hopefully I'll be able to take a look at it later today.

PlainBill

[RobertoIsRad]

Re: No power on a Acer AL1916

Board #1
Black on left pin:
Middle - .914
Right - The numbers rise until 1.0 and then stop
Black on middle pin:
Left - .153
Right - 1.858
Black on right pin:
Left - .743
Middle - .726

Board #2 The one that looks fried
Black on left pin:
Middle - .548
Right - 1.103
Black on middle pin:
Left - .147
Right - .750
Black on right pin:
Left - .719
Middle - .658

I found a service manual for a AL1916v I think my model is an A (I can't find that one though...). At the end of the manual there are diagrams. I wonder if this would help with finding correct readings, unfortunately I don't really know what any of it means...

[PlainBill]

Re: No power on a Acer AL1916

Board #1 Starting from the top:
Left - 3.34
Middle - 2.50
Right - 2.66

Top - 4.72
Middle - 3.34
Bottom - 0.00

Board #2 Starting from the top:
Left - 3.34
Middle - 2.50
Right - 2.66

Top - 4.71
Middle - 3.35
Bottom - 0.00

I've attached bigger pictures of the transistor. I would agree that something definitely looks wrong in pic #2.
Also this monitor does have a LED on the power button, but currently does not light up

I'm afraid I would have to compare the results to a known good board to make any sense of them. They aren't what I was expecting, but it was a tenuous hope at best.

That first picture is amazing. Great photography. And it's good to know that we haven't been trying to get an LED to work that doesn't really exist.

As far as the discolored transistor, try using the diode test range on your DMM. Do this with the power disconnected. Put the black probe on one lead of the transistor and note the reading when you touch the red probe to each of the other leads. Now move the black probe to the second lead and repeat; and finally move the black probe to the third lead. Then do the same thing on the same transistor on the second board.

PlainBill

[RobertoIsRad]

Re: No power on a Acer AL1916

Board #1 Starting from the top:
Left - 3.34
Middle - 2.50
Right - 2.66

Top - 4.72
Middle - 3.34
Bottom - 0.00

Board #2 Starting from the top:
Left - 3.34
Middle - 2.50
Right - 2.66

Top - 4.71
Middle - 3.35
Bottom - 0.00

I've attached bigger pictures of the transistor. I would agree that something definitely looks wrong in pic #2.
Also this monitor does have a LED on the power button, but currently does not light up

[PlainBill]

Re: No power on a Acer AL1916

That's kinda good news at least. Here are the pictures. The flash kind of ruins the pictures but it's too dim right now. I'll take more pics tomorrow morning if I have to.

They are fine. As usual, I've been busy drawing circles. This is the usual drill; put the logic card into the monitor, hook the monitor up to power. The black lead would go to the screw in the hole circled in black (or directly to the solder area). Measure the voltages at all three pins of each of the two voltage regulators circled in blue.

Now for something exotic. Note that I have circled a transistor in red. That looks like it might be discolored.

NOW, a lot of this has been based on the assumption that the monitor has a power led. I've never seen an LCD monitor without one, but there always is a first time. Would you please check that out.

PlainBill

[RobertoIsRad]

Re: No power on a Acer AL1916

That's kinda good news at least. Here are the pictures. The flash kind of ruins the pictures but it's too dim right now. I'll take more pics tomorrow morning if I have to.

[PlainBill]

Re: No power on a Acer AL1916

Thanks for your help! Here's what I found:

Board #1 Large Capacitor - 165 volts
Black - 0.01
Brown - 4.54
Red - 14.62
Orange -0.00
Yellow - 5.00
Green - 5.00
Blue - 0.00
Black - 0.00

Board #2 Large Capacitor - 162 volts
Black - 0.01
Brown - 4.53
Red - 14.68
Orange - 0.00
Yellow - 4.98
Green - 4.99
Blue - 0.00
Black - 0.00

Good work! Now the bad news. Those voltages are approximately what I would expect from a good board. Even if the inverter were bad, the led in the power button should light up.

The next thing to do would be to post top and bottom pictures of the logic board.

PlainBill

[RobertoIsRad]

Re: No power on a Acer AL1916

Thanks for your help! Here's what I found:

Board #1 Large Capacitor - 165 volts
Black - 0.01
Brown - 4.54
Red - 14.62
Orange -0.00
Yellow - 5.00
Green - 5.00
Blue - 0.00
Black - 0.00

Board #2 Large Capacitor - 162 volts
Black - 0.01
Brown - 4.53
Red - 14.68
Orange - 0.00
Yellow - 4.98
Green - 4.99
Blue - 0.00
Black - 0.00

[PlainBill]

Re: No power on a Acer AL1916

Knowing the caps on this board, it seems likely that they will require a replacement of all caps. That's going to cost less than $10 for each monitor. But let's not jump to conclusions just yet.

PlainBill