Proview PL926Wbi, no power

[SBlackfoot]

Hi guys,

I have a Proview LCD here that isn't cooperating. No signs of life at all, not even a flash from the power indicator light. What I have tried thus far:

1. First thing I did was check the three fuses that I found on the inverter board, all check out fine.

2. I checked for continuity on all of the transformers and their windings seem okay too.

3. The caps all looked fine but I replaced 'em anyway, all but the big one. I also touched up that ugly solder joint between the two transformers, to the right of C12.

4. I've checked the power switch and the wiring all the way to the logic board, it checks out.

5. Without the logic board connected I get around 160v at the large capacitor, +5.0v at the +5v pins to the logic board, and +14.9-15.1v on the +14v rail along with a very faint hum.

This leads me to believe that it's a logic board problem...

And that leaves me at a loss. Any suggestions? Can I do something to the BLON pin (+5v, ground, etc?) to jump the inverter, to see if it and the backlights even working at all? My apologies for the lack of a pic of the underside of the logic board, my batteries died and I was lucky to get the topside pic. Plus the light isn't the greatest at this hour, I'll get sharper ones if need be.

[jetadm123]

Re: Proview PL926Wbi, no power

Good work on troubleshooting thus far. On your logic board, try measuring the voltage at each leg of the voltage regulator U10. Also, what's the part number stamped on U10 (I'm guessing 1117-33?)?

[retiredcaps]

Re: Proview PL926Wbi, no power

5. Without the logic board connected I get around 160v at the large capacitor, +5.0v at the +5v pins to the logic board, and +14.9-15.1v on the +14v rail along with a very faint hum.

This leads me to believe that it's a logic board problem...

Is the 5V present on the logic board when it is connected?

[SBlackfoot]

Re: Proview PL926Wbi, no power

Thanks for the responses gentlemen. I'm afraid I'm just about at my limit knowledge-wise so I may need a little more instruction.

1. I'm not sure how to measure the regulator (U10). From ground to each of the three legs from left to right I get 0v, 1.25-1.26v, and 4.68v, while the top contact gets 1.25-1.26v. From the top contact to the other three I get -1.25v, 0v, and 3.42v.

2. It is indeed an AS1117L-33, good call.

3. I'm also not sure where to probe for power, but judging by the regulator's behavior I'd guess that 5v is present?

Thanks again guys. :^)

[retiredcaps]

Re: Proview PL926Wbi, no power

From ground to each of the three legs from left to right I get 0v, 1.25-1.26v, and 4.68v,

As usual, jetadm123's diagnosis is correct. Your U10 is bad. The part number's suffix, -33, indicates that the correct output voltage should be 3.3V. You have 1.25V so it is definitely bad.

[retiredcaps]

Re: Proview PL926Wbi, no power

If you have old junk boards like a sound card, the AS1117L-33 are "jellybean" parts and quite common. You can reuse an old one if you can find it. Otherwise, you can see if your local electronics store has them.

If you want to order off the Internet, you can get it from digikey or ebay. I find ebay cheaper, but the wait is longer. Digikey charges a minimum $8 for shipping and handling to Canada.

Here is an ebay auction for 5x LM1117-33 for $1.59 + free shipping.

http://www.ebay.ca/itm//400280532968

[retiredcaps]

Re: Proview PL926Wbi, no power

BTW, here is a simple way to test a voltage regulator once you remove it. This will verify that the regulator is bad out of circuit. As you can see, this is a good 3.3V fixed regulator (that I ordered off ebay).

I use a heat gun on low heat to remove these types and I use Kapton tape to cover all the surrounding components so they are not damaged by the heat from the heat gun. With this method, it takes about 30 seconds to remove.

[sabre504]

Re: Proview PL926Wbi, no power

Hi i have attached a pic
Place black probe on yellow leg this is ground

Red probe on red leg this is input report reading (approx 5v)

then red probe on green leg this is output and report reading (approx 3.3v)

From what you first measured you seem to only be getting 1.26 v out if this is the case when you remeasure then you may have a faulty reg

Ah retiredcaps beat me again

[retiredcaps]

Re: Proview PL926Wbi, no power

1. I'm not sure how to measure the regulator (U10). From ground to each of the three legs from left to right I get 0v, 1.25-1.26v, and 4.68v,

You did it correctly above. Just verify as sabre504 writes that the middle pin is 1.25V.

[jetadm123]

Re: Proview PL926Wbi, no power

If you have old junk boards like a sound card, the AS1117L-33 are "jellybean" parts and quite common. You can reuse an old one if you can find it. Otherwise, you can see if your local electronics store has them.

If you want to order off the Internet, you can get it from digikey or ebay. I find ebay cheaper, but the wait is longer. Digikey charges a minimum $8 for shipping and handling to Canada.

Here is an ebay auction for 5x LM1117-33 for $1.59 + free shipping.

http://www.ebay.ca/itm//400280532968

Amazing! 5 regulators for $1.59 with free shipping from China to boot! Man, how do they make any money off of it???

[retiredcaps]

Re: Proview PL926Wbi, no power

Amazing! 5 regulators for $1.59 with free shipping from China to boot!

I don't know, but I recently got 10 fixed 3.3V and 10 adjustable for a total of $2 + free shipping.

[SBlackfoot]

Re: Proview PL926Wbi, no power

I use a heat gun on low heat to remove these types and I use Kapton tape to cover all the surrounding components so they are not damaged by the heat from the heat gun. With this method, it takes about 30 seconds to remove.

Place black probe on yellow leg this is ground

Red probe on red leg this is input report reading (approx 5v)

then red probe on green leg this is output and report reading (approx 3.3v)

Done. Yellow to red is 4.68v, yellow to green is 1.25v. I'll have to try and remove the regulator next. Once I find some Kapton tape... Or would a heat shield out of stainless steel work? I work with sheet metal, anything is possible. Heck even a piece of insulating wool...

Has anyone ever told you that you guys are awesome? lol

If you have old junk boards like a sound card, the AS1117L-33 are "jellybean" parts and quite common. You can reuse an old one if you can find it. Otherwise, you can see if your local electronics store has them.

Funny. I have a (working) PCIE-SATA card on my desk. Sure enough, it has three! I bet I can find another somewhere.

[retiredcaps]

Re: Proview PL926Wbi, no power

DOr would a heat shield out of stainless steel work? I work with sheet metal, anything is possible. Heck even a piece of insulating wool...

I have used some aluminum foil in the past. I suggest removing TC13 (cap) first because it may not survive the heat even with the aluminum foil.

Funny. I have a (working) PCIE-SATA card on my desk. Sure enough, it has three! I bet I can find another somewhere.

Yes, they are common parts.

[SBlackfoot]

Re: Proview PL926Wbi, no power

For a common part, I sure am having trouble finding one of those regulators. Like I said, there are three on my perfectly working SATA card. I rummaged through my parts pile last night (sound/video/network cards, motherboards, etc...) and found exactly zero more. I can't even find any in the Acer or Phillips monitors that I've been scavanging parts off of.

The first electronics store I went to could get them, although a slightly different model number, but they want a $20 minumum quantity. Around 13 pieces. I just want one. The second store couldn't even source that, they're usually not THAT clueless.

I might be stuck waiting the 40 days shipping from China and going the eBay route. *sigh*

[SBlackfoot]

Re: Proview PL926Wbi, no power

Actually the shipping looks better than I thought, only two or three weeks if I'm lucky. The 40 day estimate was from a USB breakout board that I've been waiting for since late May. Ugh...

[retiredcaps]

Re: Proview PL926Wbi, no power

I can't even find any in the Acer or Phillips monitors that I've been scavanging parts off of.

Post some pics of the logic boards of these monitors. Sometimes they go by other part numbers. For example, a 1084-33 will should work as well.

I might be stuck waiting the 40 days shipping from China and going the eBay route. *sigh*

I can send you one (via letter mail) if you make a donation to one of the following charities:

1) Parkinson’s disease
2) The War Amps of Canada
3) Drop in a few more coins for the Poppy Campaign in November

You will get the one I tested in the picture.

Of course, Canada Post may just be as slow as stuff from China!

[SBlackfoot]

Re: Proview PL926Wbi, no power

I'll see what I can do about getting some pics of the other boards. I might want to keep that Acer board as-is though, I know it worked and would hate to kill a known-good logic board on a fairly common monitor. Maybe I'll take a closer look through my old-cards pile, I really didn't have alternate part numbers in mind. No 1117? Back in the pile...

How long did it take you to get those parts in from China? I appreciate the offer of sending one but I'd never ask you to go out of your way like that, you've already done so much to help.

For what it's worth, I drop some paper in those collection boxes every year (I figure it helps more, and is easier for the Vet to carry than those heavy coins.) and wear my poppy with pride.

[retiredcaps]

Re: Proview PL926Wbi, no power

How long did it take you to get those parts in from China?

I'll have to look that up when I'm on a different computer, but I think it was 3 weeks.

If your other item is past 40 days, send an email to the seller. Most China based sellers will give you a full refund. I had 1 item that didn't arrive after 7 weeks. I sent an email saying it has been 7 weeks and I immediately, without complaint, got a full refund and apology from seller.

I know most people have a dim view of ebay and China based sellers, but my experiences have all been largely positive. I know it works to my advantage when people think they are rip-off artists because I have less people competing for the same items.

[retiredcaps]

Re: Proview PL926Wbi, no power

How long did it take you to get those parts in from China?

Bidding ended April 26 and I received the item on May 14, so about 3 weeks. YMMV.

[SBlackfoot]

Re: Proview PL926Wbi, no power

Coincidentally enough my other China purchase arrived today. It took six and a half weeks, so right in the middle of the projected 40-50 days promised by the auction (including weekends). For a dirt cheap custom ALDL cable for my car I can't complain.

I used the link you provided above and purchased the cheap regulators from eBay. Hopefully they're less than 40 days. In the meantime I slapped the LCD back together and will move on to the next one...