Lenovo ThinkVision L191 19" goes blank after <1 sec

[jonathanku]

Hi all, I'd like help in determining whether this issue is likely due to bad caps or not.

Hardware: Lenovo ThinkVision L191 (19"), black, from 2nd-hand shop.

Symptoms:

• The monitor switches on and the ThinkVision logo appears on screen, but only for less than a second, then it goes blank (led stays on - not sure if it's green or changes to yellow - I'm a shade color blind!).
• Similarly if I hit the function-F4 thing on my laptop, the desktop appears on screen for a moment then disappears again. Similar behaviour on multiple PCs.

Could that indicate a bad-capacitor issue? Here are photos from a couple of different angles:
http://i915.photobucket.com/albums/a...pairs/img2.jpg
http://i915.photobucket.com/albums/a...pairs/img1.jpg

Any thoughts appreciated.

[retiredcaps]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

It looks like someone already tried to recap this because I think I see United Chemicon and Rubycon caps on it? Unless Lenovo spent some $$$ and got quality caps to begin with. When was this monitor made?

What you are describing is "2 seconds to black".

You can search this forum for what others have done, but it could be a number of things

1) bad CCFLs
2) bad transformers
3) bad PNP transistors (like c5707)
4) bad caps
5) poor cold/dry solder joints
6) possibly something else

Symptoms:

• The monitor switches on and the ThinkVision logo appears on screen, but only for less than a second, then it goes blank (led stays on - not sure if it's green or changes to yellow - I'm a shade color blind!).
• Similarly if I hit the function-F4 thing on my laptop, the desktop appears on screen for a moment then disappears again. Similar behaviour on multiple PCs.

Could that indicate a bad-capacitor issue?

[jonathanku]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

Thanks for that, sounds like it could be a lot to check.

Could the caps sitting at an angle indicate that they've blown? I've recently read that that could be the case.

p.s. I don't know when the monitor was made. I could get a serial number and see if that indicates anything. I'm guessing 4-5 years old max.

[retiredcaps]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

2 seconds to black takes time to troubleshoot, but it is solvable. I know I learn a lot solving these type of problems versus the "simple" recap.

If the caps sit at an angle, it could be sign that the "bung" is leaking or bloated on the bottom. Most of the pics show the tops or vents blown, but one monitor I fixed and the caps blown on the top and bottom.

Most of the monitors have a manufacture date on a sticker on the back.

What is the date code on the caps? It should be something like

Rubycon MCZ
T0934
105C

T0934 -> 2009 week 34

or

KCZ 0832 105C

0832 -> 2008 week 32

sounds like it could be a lot to check.

Could the caps sitting at an angle indicate that they've blown?

p.s. I don't know when the monitor was made.

[jonathanku]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

Thanks again Retiredcaps. Monitor was manufactured in June 2008, don't yet have dates for the caps... I've actually put the monitor back together to go and negotiate a partial-refund. I'll feed back later!

[jonathanku]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

Update - the supplier agreed it was faulty and gave it to me for £10. Can't complain.

So, on to the troubleshooting. I'll check the capacitor dates later today. I'll also have a closer look underneath the squinty caps to see if they're bloated.

[jonathanku]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

The caps seem to be 0806, a couple of 0810 and an 0816... can't see them all.

Another update - looks like the image is still there after the monitor goes "off" - i.e. I think the backlight is just going off - if that helps?

[retiredcaps]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

So it looks like from the date codes these are the original caps if the Lenovo was made in 2008.

What are the brand names on them? I just took a guess from your pictures, but I'm pretty sure the brown ones are UCC and the ones with the "K" vent are Rubycons.

The image still being there is consistent with 2 seconds to black. If you shine a flashlight from the back, you should see the image without the backlight being on.

So if you go back to post #2, start checking those items (in no particular order). I have been reading this forum for about 2 months and I can't say one problem is more likely than the other. And I don't see Lenovo mentioned much here.

You can search each item in this forum separately for more detailed info and how to test each one. Here is an example of a bad/burnt CCFL connection and broken CCFL.

https://www.badcaps.net/forum/showthread.php?t=10078

Pay particular attention to the posts by PlainBill.

Also it would help if you posted pictures to this forum after reading the FAQ. People will want to see clear focused pics of the top and bottom of each board (power and logic) separately. So you should post 4 pics in total.

The caps seem to be 0806, a couple of 0810 and an 0816... can't see them all.

Another update - looks like the image is still there after the monitor goes "off" - i.e. I think the backlight is just going off - if that helps?

[PlainBill]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

To add my $.02 worth, I am especially interested in pictures of the back of the inverter, and the part number of the inverter controller (usually a 16 or 20 pin chip).

PlainBill

[jonathanku]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

Thanks. Yeah, date-wise that seems likely. And yes, the ones which I can see a brand on are Rubycon; the slightly bigger ones near the ribbon cable on the small board don't seem to have branding - though I could be missing it.

More pictures below to cover both boards. I'll do some more reading on existing posts. Thanks again for your help.

Large board, front:
http://i915.photobucket.com/albums/a...pairs/img1.jpg
Large board, back:
http://i915.photobucket.com/albums/a...s/IMG_3655.jpg
Small board, front:
http://i915.photobucket.com/albums/a...s/IMG_3654.jpg
Small board, back:
http://i915.photobucket.com/albums/a...s/IMG_3656.jpg

[jonathanku]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

PlainBill - I have to admit, I don't yet know what part the inverter is - I'm guessing something to do with converting AC to DC? Is it the cuboid grey box beside the largest of the capacitors? I'll have a look for a 16 or 20 pin chip and post back - though probably later; it's now bed time unfortunately. Work in the morning.

[PlainBill]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

PlainBill - I have to admit, I don't yet know what part the inverter is - I'm guessing something to do with converting AC to DC? Is it the cuboid grey box beside the largest of the capacitors? I'll have a look for a 16 or 20 pin chip and post back - though probably later; it's now bed time unfortunately. Work in the morning.

It doesn't matter. Until you learn to follow directions and attach the pictures properly I have no intention of helping you. I've had more than enough problems with things posted at outside sites.

PlainBill

[jonathanku]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

Thanks PlainBill - I completely agree. Hands-up and admit that I didn't fully read the forum rules. The picture guidelines are ideal.

Attached are more appropriate images of the front and back of both boards - as clear as I could manage, and I'll follow-up later after I've hunted for the inverter-controller.

Here's the back of the bigger board as that might be of interest:

[PlainBill]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

Thanks PlainBill - I completely agree. Hands-up and admit that I didn't fully read the forum rules. The picture guidelines are ideal.

Attached are more appropriate images of the front and back of both boards - as clear as I could manage, and I'll follow-up later after I've hunted for the inverter-controller.

Here's the back of the bigger board as that might be of interest:

The inverter controller is the IC circled in red. What is the part number, please.

This design is unusual. It uses two transformers and a Royer oscillator. It does not have an output voltage limiting, so the controller is detecting an open lamp condition. What is the resistance between the points marked A - A' and B - B'?

PlainBill

[jonathanku]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

Sorry for the delay - dad/husband duties were calling. That part number is 7BA11DM TL1451AC. Here's a closeup:



p.s. - this image is upside-down relative to the big image above.

[el3ctroded]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

When doing LCDs like this, step 1 for me is to determine if all the CCFLs are Ok.

To easily do that, I connect a single CCFL at a time and see if it lights up at all. Do for each CCFL. If one does not light up, or is pinkish, there's a culprit.

If they all light up and none are failing (the pinkish color) then I start with the electronics.

The next step is to try one of the known good CCFL's on each of the connectors. See if it lights up on each connector. If one doesn't work, there's the culprit.

[jonathanku]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

When doing LCDs like this, step 1 for me is to determine if all the CCFLs are Ok.

Thanks for the input el3ctroded. I've just tested that, but get the same behaviour when each of the CCFLs are connected on their own (i.e. I see the picture for a second then it dissapears).

[retiredcaps]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

Did you measure this for PlainBill?

What is the resistance between the points marked A - A' and B - B'?

PlainBill

[jonathanku]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

Ah yes, sorry - here's the resistance info PlainBill asked for:

A - A' was 2.28 (on the 20k setting, I'm guessing that's 2.28kΩ ..?)
B - B' was 2.27

-JK

[PlainBill]

Re: Lenovo ThinkVision L191 19" goes blank after &lt;1 sec

Ah yes, sorry - here's the resistance info PlainBill asked for:

A - A' was 2.28 (on the 20k setting, I'm guessing that's 2.28kΩ ..?)
B - B' was 2.27

-JK

That indicates the transformers match to within 1% - good enough. Which probably means either a problem with a return line, or an aging CCFL that's drawing too much current. The inverter controller is a TL1451AC; the same as used in Dell monitors.

I AM going to need a better picture of the back side of the power supply / inverter card, preferably get as close to 2000 x 2000 pixel resolution as possible. We're going to be tracing some circuits.

PlainBill