Acer AL1706b - No Power

[bw1]

I started replying in another thread but didn't want to hijack that and confuse people with my responses.

My previous post(s) are below:

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I've got an AL1706b that's completely dead - no led, no power, nothing.

Input fuse @ 2A/250v checks out, and all caps visually look good. No leaks, no bulges.

This is the Rev: C board dated 2005.11.04 and was working perfectly until a couple days ago.

I know caps can look fine and be bad, but I don't want to waste my time replacing a bunch of caps to find out it's something else. It'd be one thing if I had the assortment here already, but most of these would be custom-order, which only adds to the hassle.

Thanks!

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((REPLY FROM RETIREDCAPS))

It sounds like you have a multimeter. If you know how to use it, see if the secondary voltages, usually 5V DC and/or 12VDC, are present on the connector between the power board and logic board.

If not, carefully measure the DC voltage across the main filter capacitor. It should be 1.4 * mains.

Post clear focused pictures AFTER reading

https://www.badcaps.net/forum/showthread.php?t=1868

Please do not post pictures inline.

Take your boards to a window on a sunny day, turn flash off, and use macro mode. Take a top down view of all your boards (front and back). Make sure the photo is legible so that we can read the PCB printing clearly. A shutter speed of 1/125 or faster will produce nice clear focus pictures. Try to get a photo that is 2000x2000 resolution or as close as possible.

Here is an example of the pictures we want.

https://www.badcaps.net/forum/showpos...94&postcount=1

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I'm on the way out the door to a wedding so will post more details/pics when I get back.

Quick measurements show that both 5v leads going to logic board are good, doesn't look to be a 12v line, and there is minimal voltage (around 1v or so if I remember correctly - I don't know the spec though) on the other non-ground leads as well. Voltage at main cap is ~170v.

Probably doesn't help without any more info though - I'll get to that when I return.

I hate to hijack a thread - if this belongs on its' own, feel free to split it!

Thank you.

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Photos attached below.

[jetadm123]

Re: Acer AL1706b - No Power

Quick measurements show that both 5v leads going to logic board are good, doesn't look to be a 12v line, and there is minimal voltage (around 1v or so if I remember correctly - I don't know the spec though) on the other non-ground leads as well. Voltage at main cap is ~170v.

Probably doesn't help without any more info though - I'll get to that when I return.

I hate to hijack a thread - if this belongs on its' own, feel free to split it!

Thank you.

===============================

Main cap voltage looks good assuming you're in the USA?


You should have 12V because that what's required to supply the inverter. In your third photo, you have two devices mounted to the heatsink, D803? and D805. These are probably duo diode packs outputting the 5v and 12v. With your meter, measure the middle pin voltage of each device and report your findings.

[bw1]

Re: Acer AL1706b - No Power

Main cap voltage looks good assuming you're in the USA?


You should have 12V because that what's required to supply the inverter. In your third photo, you have two devices mounted to the heatsink, D803 (correct)? and D805. These are probably duo diode packs outputting the 5v and 12v. With your meter, measure the middle pin voltage of each device and report your findings.

Yes, I'm in the USA.

D805 = 5v
D803 = 13.42v

[jetadm123]

Re: Acer AL1706b - No Power

Good! now to check the filter caps for the 12v output. Without a schematic, you'll have to trace the middle leg of D803 to the "+" leg of the filter caps. I'm thinking C808 and the smaller one next to it (there may be others). They are probably rated at 16V or 25V? Once you determine if these are the caps, measure the voltage across them.

[bw1]

Re: Acer AL1706b - No Power

Voltage across requested caps is as follows:

C808 = 13.39v
C810 = 13.39v

[PlainBill]

Re: Acer AL1706b - No Power

A rule of thumb for troubleshooting monitors: If you have the proper output voltages from the power supply but even the power LED won't come on, focus your attention on the logic card.

Understand, the power LED is controlled by the processor chip on the logic card. If the processor isn't working , no power LED.

There are several common failures I have seen. First, note that the firmware is loaded from U106. If that is corrupt, the processor is dead.
Second, note U102. That is a voltage regulator - 1.8 volt I think - the full part number will tell the tale. Check the voltages on it. A number of them fail high, destroying the processor. Also, check U101.
And for the good news, there have also been cases of failures caused by dead rest controllers. What is the location code for the three terminal device just above and to the right of the 6 pin connector? If it starts with a U, that could be the reset controller.

PlainBill

[bw1]

Re: Acer AL1706b - No Power

U102:
=========
Pin1 = 0v
Pin2 = 1.8v
Pin3 = 5v
Pin4 = 1.8v

U101: (above 6-pin at very top above caps)
=========
Pin1 = 0v
Pin2 = 1.35v
Pin3 = 5v
Pin4 = 1.35v

The three pin you are referring to (tiny little guy right below the two caps) is Q104.

U106 - is there any way to test this one if that's a possibility? (this is the one with the green+gold dots on it)

[retiredcaps]

Re: Acer AL1706b - No Power

U101: (above 6-pin at very top above caps)
=========
Pin1 = 0v
Pin2 = 1.35v
Pin3 = 5v
Pin4 = 1.35v

I think I can see 33 for the suffix on U101. If correct, U101 is bad. It should be measuring 3.3V DC.

[bw1]

Re: Acer AL1706b - No Power

U101:
=========
A1
AS1117L-33
B0548

Yeah that makes sense now that you point out the suffix (I'm learning here.) So, if that's the problem, was it likely caused by something else, or do those typically fail alone?

[retiredcaps]

Re: Acer AL1706b - No Power

Yeah that makes sense now that you point out the suffix (I'm learning here.)

While troubleshooting one of my LCDs, I was measuring up to 7 voltage regulators. So I downloaded all the datasheets and did my research. It's scary now that I even know the chip number off the top of my head.

So, if that's the problem, was it likely caused by something else, or do those typically fail alone?

I haven't run into a single bad voltage regulator, but my experience is only 5 months and 17 LCD monitors. So I can't say if they fail on their own or due to something else.

Others will probably chime in with their years of industry experience.

[retiredcaps]

Re: Acer AL1706b - No Power

U101:
B0548

B0548 is probably a date code for made in 2005 week 48.

[bw1]

Re: Acer AL1706b - No Power

I'll wait to hear any recommendations here. I'm new to component-level troubleshooting, but have soldered for years.

I don't have any money in this monitor, so am willing to spend a bit on parts assuming a decent chance at fixing.

Most of all, I'd like to gain experience and knowledge w/the troubleshooting process.

Does anyone have any recommendations here?

[retiredcaps]

Re: Acer AL1706b - No Power

I don't have any money in this monitor, so am willing to spend a bit on parts assuming a decent chance at fixing.

From what I can tell, these 5V to 3.3V DC voltage regulators are pretty common. You might even have one on a junked board?

On digikey, it looks like a replacement will cost around 78 cents.

[bw1]

Re: Acer AL1706b - No Power

AS1117 search at Digikey (had already looked there before you said anything) doesn't find anything. What are you searching for?

[retiredcaps]

Re: Acer AL1706b - No Power

AS1117 search at Digikey (had already looked there before you said anything) doesn't find anything. What are you searching for?

1117-33 is what I used for search term. AS (Alpha Semiconductor) is just one manufacturer of the 1117 chip.

[jetadm123]

Re: Acer AL1706b - No Power

AS1117 search at Digikey (had already looked there before you said anything) doesn't find anything. What are you searching for?

Great input from PlainBill. Good info to know. On Digikey you can also search for LM1117 (made by National Semiconductor), select the 3.3V option for voltage output. If you purchase through digikey, you might also want to replace all your caps (except the large one) with Panasonic FM or FC series caps, also available through digikey.

[PlainBill]

Re: Acer AL1706b - No Power

AS1117 search at Digikey (had already looked there before you said anything) doesn't find anything. What are you searching for?

The '1117-xx' parts are 'jelly bean' parts. Made by many manufacturers, pretty much interchangeable. It's rare that they fail, but a typical logic card will have two or more so even 'rare' will show up now and then. And they represent one of the few readily replaceable ICs on the logic card Failing low isn't a problem. Failing high will usually burn out the processor.

As far as U106, those are a real problem. You would want to use a new part (inexpensive), you need the firmware (very difficult to find), and a programmer (expensive) with the proper adapter. Pers Hansson is the only person I know of who succeeded in fixing a monitor that way.

PlainBill

[bw1]

Re: Acer AL1706b - No Power

So replacing the 1117 has a somewhat decent chance of fixing it? Not worth dealing with? The part itself is cheap, but there's shipping and waiting, plus chance of being more bad parts.... Recommendations?

[retiredcaps]

Re: Acer AL1706b - No Power

So replacing the 1117 has a somewhat decent chance of fixing it? Not worth dealing with? The part itself is cheap, but there's shipping and waiting, plus chance of being more bad parts.... Recommendations?

Shipping from digikey.com is less than $2.75 USD using USPS 1st class mail and I believe you get it in 48 hours. If it were me and I lived in USA, I would replace the voltage regulator and hope U106 is working properly.

Since I'm in Canada, shipping for us Canadians is $8 USD so I would either "save up" for a big order or look on a junk board or ebay.

[jetadm123]

Re: Acer AL1706b - No Power

So replacing the 1117 has a somewhat decent chance of fixing it? Not worth dealing with? The part itself is cheap, but there's shipping and waiting, plus chance of being more bad parts.... Recommendations?

Here's my two cents worth: You've got a dead monitor that's probably close to 4 years old. A bad voltage regulator has been found. If all you do is replace the regulator and let's say it works, then you'll probably need to replace the caps in maybe a year or next month, which is why I recommended replacing the caps along with the regulator. Or, depending on how much you used the monitor, those backlights could be near the end of their life. So far, it's cost you nothing except for some time taking voltage measurements. If spending $11-$12 on a fix that may not work doesn't appeal to you, then sell the monitor on craigslist for $10 and along with the $12 in parts money buy yourself a new larger screen monitor. The cost is nothing like it was 3-4 years ago and you get a warranty and added reliability (hopefully) to boot.