HP Monitor Mash-up

[branch592]

I picked up an HP w1907 LCD display with the 2 second to black problem at my local Goodwill outlet store. Took it apart looking for bad caps but found no obvious problems. Tested the monitor again and found an all white screen. Playing around with it, I discovered that reversing the top two CCFLs make the backlight work until power save mode kicked in. Noticed later that the LVDS cable had a small tear in it. Thought that was the cause of the all white screen, but found out later it probably isn't.

So I picked up an HP L1908w display at the same store a few days later, planning to use its LVDS cable to fix the first one. But things haven't been that easy.

Both monitors use the same power boards and logic boards. They use different revisions of the lcd panel (Innolux MT190AW01 versions 3 and 5). The L1908w lacks the speakers and associated electronics on the power board, and lacks the DVI input on the logic board.

The power board contains the inverter, AC supply and the sound circuitry (if needed). It only supplies 5V to the logic board. The logic board contains circuitry to produce the needed lower voltages. Specifically the AS1117-L
versions -33 and -18. And it also has electrolytic capacitors from Samxon and Su'scon.

Pulled the ccfl holders from the 1907w panel, figuring to repair them and then use them to repair the other panel. But there is no apparent damage to them.

Tested the second monitors backlight by reversing the top ccfls and they worked until power-save mode kicked in (no computer attached). Decided to use that LCD display since the cable was stuck to the LCD panel really well and I was being very careful not to damage the LVDS cable.

But the LCD panel(version 5) will not work with the w1907 logic board. Always get the white screen, even after switching power boards. Tests OK with the L1908w controller card.

So now to the questions:

1. Is it likely the problem is a incompatibility between the logic board and the LCD panel? Or would a recap help? Or did I do damage to the board?

2. Does the change in behavior of the ccfls after reversing their positions on the power board mean a problem with the ccfls or the power board?

3. The Samxon datasheet lists the impedence in ohms. The DigiKey website also uses mOhm. Is this Milli-, so that Impedance at 0.038 Ohms translates to 38 mOhms? Got to the decimal place in the right place.

4. Since some of the caps on the logic board are for the power supply, shouldn't they be low ESR? Or does that matter with the AS1117 chips?

5. Recapping the boards make sense for reliability, but could they cause the problems I've noted?

Now for the technical details and photographs:

Monitor 1:
HP Model w1907
Assembly No. 435820-101
Manufactured July 2008
Product Number RK283AA
Regulatory Model NO. HSTND-2261-F
REV ITM001
Product of (Shen Zhen) China


Monitor 2:
HP Model L1908w
Assembly No 454440-101
Manufactured September 2008
Product No. GP536A
Regulatory Model NO. HSTND-2351-F
REV ITM002
Spares No. 457515-001
Product of (Shen Zhen) China


Power Board -- ILPI-027, Rev A, 2007.01.15

C804 - Su'scon SE - 18mm x 40mm - 7.5mm leads - 105C 100uF 450V Ripple=720 - Not to be replaced

C807 - Su'scon SH - 6.3mm x 11mm ??? - 125C 47uF 25V Ripple=110
Note: size not in datasheet
C820 - Su'scon SH - 6.3mm x 11mm ??? - 125C 47uF 25V Ripple=110
Note: size not in datasheet
C818 - Samxon GK(M) - 10mm x 16mm - 5.0mm leads - 105C 1000uF 10V Ripple=1430 Impedance=0.038
C509 - Samxon GK(M) - 10mm x 16mm - 5.0mm leads - 105C 470uF 25V Ripple=1430 Impedance=0.038
C817 - Samxon GK(M) - 10mm x 16mm - 5.0mm leads - 105C 470uF 25V Ripple=1430 Impedance=0.038
C815 - Samxon GK(M) - 12.5mm x 20mm - 5.0mm leads - 105C 1000uF 25V Ripple=2360 Impedance=0.021

Sound Subsytem - For Future Reference - NOT to be replaced

C701 - Su'scon SH - 10mm x 13mm - 5.0mm leads - 125C 220 uF 16V Ripple=300
C702 - Samxon GK(M) - 10mm x 16mm - 5.0mm leads - 105C 470uF 25V Ripple=1430 Impedance=0.038
C705 - Samxon BD(M) - 10mm x 15mm ??? - 125C 470uF 16V Ripple=256
Note: size not in datasheet
C707 - Samxon BD(M) - 10mm x 15mm ??? - 125C 470uF 16V Ripple=256
Note: size not in datasheet
C713 - Su'scon SE - 5mm x 11mm - 2mm leads - 105C 10uF 25V Ripple=45



Logic Board -- ILIF-027 Rev A, 2006.10.25

C152 - Samxon KM(M) - 5mm x 11mm - 2mm leads - 105C 100uF 16V Ripple=125
C138 - Samxon KM(M) - 5mm x 11mm - 2mm leads - 105C 100uF 16V Ripple=125
C135 - Samxon KM(M) - 5mm x 11mm - 2mm leads - 105C 100uF 16V Ripple=125

C144 - Su'scon SK - 5mm x 11mm - 2mm leads - 105C 22uF 16V Ripple=63
C132 - Su'scon SE - 5mm x 11mm - 2mm leads - 105C 4.7uF 50V Ripple=35
C130 - Su'scon SE - 6.3mm x 11mm - 2.5mm leads - 105C 100uF 16V Ripple=140

[retiredcaps]

Re: HP Monitor Mash-up

So now to the questions:

Easily the best post #1 this year with a ton of info, detail, and excellent photos. Hopefully my response is up to par. Thank you.

1. Is it likely the problem is a incompatibility between the logic board and the LCD panel? Or would a recap help? Or did I do damage to the board?

The caps on the logic don't undergo the same stress as those on the power board, but they can go bad.

The eeprom on the logic board might be programmed to a specific lcd panel board, but that is pure speculation on my part.

2. Does the change in behavior of the ccfls after reversing their positions on the power board mean a problem with the ccfls or the power board?

2 seconds to black can be a number of things and all are discussed starting with posts #19 and #20 at

https://www.badcaps.net/forum/showthread.php?t=10419

3. The Samxon datasheet lists the impedence in ohms. The DigiKey website also uses mOhm. Is this Milli-, so that Impedance at 0.038 Ohms translates to 38 mOhms? Got to the decimal place in the right place.

Yes, milli.

4. Since some of the caps on the logic board are for the power supply, shouldn't they be low ESR? Or does that matter with the AS1117 chips?

In general caps on the logic board are general purpose caps. However, in some large TVs, we have seen low ESR caps on the main board.

PS. While the ccfls look good, the return wire (thinner guage) on the top ccfl is sometimes burnt out and not making proper contact with the ccfl end. Alexanna has a lot of experience in repairing these types of problems and he reports that snipping off the bad wire and resoldering the ends results in a success repair.

[momaka]

Re: HP Monitor Mash-up

Easily the best post #1 this year with a ton of info, detail, and excellent photos.

Agreed.

@branch592: have you tried testing the HP w1907 by connecting it to a (turned on) computer? The reason I ask is because a white screen is usually (but not always) a t-con issue. If your monitor stays on (i.e. backlight is present too) while connected to the computer but the screen is still white, then a t-con issue is very probable.

[Scenic]

Re: HP Monitor Mash-up

1. Is it likely the problem is a incompatibility between the logic board and the LCD panel?

It shouldn't be. The only difference between the two that I could find is that V3 is one of those disgusting glare/glossy LCDs, while the V5 is a matte one.
The pinout and all the other specs seem to be identical.

edit: the LCD that always shows a white screen might not be getting any voltage. most LCDs of up to 24" are the "normally white" type, i.e. with no voltage to the T-Con (= the whole panel itself), all you see is white when the backlight is on.
So either it's not getting any voltage from the controller board (should be 5V as per the datasheets below) or a fuse on the T-Con might be bad (if it has one, which is should)

[shovenose]

Re: HP Monitor Mash-up

if the capacitors are Samxon GF or GL, even if they aren't bulged, consider replacing them.
While Samxon generally makes high quality capacitors, those two series suck.
An easy way to remeber it? Good Luck and Girl Friends are unreliable

[branch592]

Re: HP Monitor Mash-up

I think the LCD panel is probably OK. When connected to the L1908w logic board, the board that came with the panel, the proper message about no video connected is displayed. Only when I try it with the logic board from the 1907w do I get the white screen. All the power and control for the panel comes thru the logic card.

The Samxons are BD, GK, and KM.
The Su'scons are SE, SH, and SK.

[momaka]

Re: HP Monitor Mash-up

I think the LCD panel is probably OK. When connected to the L1908w logic board, the board that came with the panel, the proper message about no video connected is displayed. Only when I try it with the logic board from the 1907w do I get the white screen. All the power and control for the panel comes thru the logic card.

In that case also check the MOSFET(s) on the 1907w logic board that feed the t-con with 5V.
On the upper left corner of this picture, there are 2 MOSFETs and 1 transistor. One of the MOSFETs should be what controls the 5v rail to the t-con. So either Q405 or the one below it (I'm thinking the one below since it has thicker traces going to it). Make sure it's not open-circuited or short-circuited. I had a 17" Dell that blew this MOSFET instead of blowing the fuse on the t-con (fun!). In my case, the fault with the MOSFET was visible, though.

[branch592]

Re: HP Monitor Mash-up

Checked a couple of the fuses near the LVDS cable and found them to be good. Checked the resistance of the transistors on BOTH of the logic boards. The results follow. And a picture.

1907w Logic Board: (Problem)

Q105
S-G 1.38 M
S-D 1.4 M
G-D 5.06 K

Q106
C-B 4.5 M
C-E 4.49 M
B-E 14.84 K

Q103
S-G 290
S-D 145.6
G-D 380

L1908w Logic Board: (Working)

Q105
S-G 2.6 M
S-D 1.68 M
G-D 9.72 M

Q106
C-B 5.36 M
C-E 5.32 M
B-E 14.92 K

Q103
S-G 98.8 K
S-D 8.93 M
G-D 9.2 M


None of them are shorted, and I'm assuming their ok.
Will procede to recap once I get the parts ordered in a week or so. Looks like it might be harder to recap the logic board due to the smaller looking spots on the back of the board. Will have to be more careful where the solder goes.

[branch592]

Re: HP Monitor Mash-up

Current capacitor replacement plans (subject to change due to availability). All from Digi-Key.

Power board:
Su'scon SH 125C 47uF 25V--> Nichicon BT 47uF 25V Larger than original but looks like it will fit. Due to location on the high side of board when installed and near large heatsinks, keeping 125C rating seems sound.
Samxon GK 470uF 25V --> Panasonic FM 470uF 25V
Samxon GK 1000uF 10V --> Panasonic FM 1000uF 10V
Samxon GK 1000uF 25V --> Panasonic FM 1000uF 25V


Logic board:
Samxon KM 100uF 16V --> Panasonic FR 100uF 16V
Su'scon SK 22uF 16V --> Panasonic FC 22uF 25V
Su'scon SE 4.7uF 50V --> Panasonic FC 4.7uF 50V
Su'scon SE 100uF 16V --> Panasonic FR 100uF 25V

Will report progress when complete.

[dennist]

Re: HP Monitor Mash-up

I have the same problem.
Tomorrow i gone replace the Capacitors.

This i found on the www:

http://www.ebay.com/itm/Repair-Kit-H...-/230712638859

[retiredcaps]

Re: HP Monitor Mash-up

This i found on the www:

http://www.ebay.com/itm/Repair-Kit-H...-/230712638859

If you live in the USA, you can put together your own set of quality low ESR caps via digikey.com and probably pay about 1/2 price vs a kit.

[dennist]

Re: HP Monitor Mash-up

Today i chanced all capacitors exept the 4,7 uF, it did not fix the problem.
So tomorrow i gone chance also the 4,7 uf, but i don't think is fix it.

[jayoung]

Re: HP Monitor Mash-up

Did you read through the following post concerning 2 seconds to black?

https://www.badcaps.net/forum/showthread.php?t=10419

Issues can include bad capacitors, bad transformers, bad ccfl's or ccfl wiring, bad transistors, etc.

[Jmlcat]

Re: HP Monitor Mash-up

Hi there guys,

i've came across with one of these boards (ILPI-027),from a HP W1907V and i'm having some problems with it.
It had the 2 sec to black problem and by looking into the the forum descriptions, i've decided to have a go and try to repair it. I did check all the solderings and resolder all of them. The problem happened when it tried to get it running again. It started to make strange noises through the speakers and when i looked at it it was almost burning from a Schottky barrier rectifier, the D803 on the board. I've tried to find the cause but my electronics skills are few and i can't figure where to look for . At the beginning i though it was a transformer just before that part of the circuit, but i can't find the schematics for it. Hope you guys can enlighten me as for where to search or how to proceed.

Thank you all for your good descriptions.

[jetadm123]

Re: HP Monitor Mash-up

Hi there guys,

i've came across with one of these boards (ILPI-027),from a HP W1907V and i'm having some problems with it.
It had the 2 sec to black problem and by looking into the the forum descriptions, i've decided to have a go and try to repair it. I did check all the solderings and resolder all of them. The problem happened when it tried to get it running again. It started to make strange noises through the speakers and when i looked at it it was almost burning from a Schottky barrier rectifier, the D803 on the board. I've tried to find the cause but my electronics skills are few and i can't figure where to look for . At the beginning i though it was a transformer just before that part of the circuit, but i can't find the schematics for it. Hope you guys can enlighten me as for where to search or how to proceed.

Thank you all for your good descriptions.

I suggest you post some good focused top and bottom photos (like those in post #1) of your power board. Perhaps some sharp-eyed member will spot something that caused D803 to smoke.

[budm]

Re: HP Monitor Mash-up

Here are some service manuals, not sure if it will have the diagrams for the power supply/inverter board.
http://elektrotanya.com/?q=showresul...oria=&kat2=all

[Jmlcat]

Re: HP Monitor Mash-up

Thank you for your quick answer .
I'll try to do my best as for the pics and exposing my problem.
The rectifier is a sp10100c , the one next to it was almost burning too last attempts to check the power board. I've tried to check voltage on transformer SPW-055 but no joy. Let me remember that i'm a beginner with electronics but i deal with electrical devices and installations every day and i'm used to troubleshoot them.
Here, i'm stucked here because i don't know where to start looking at. Usually i start searching for evident failures like bad caps or solders, but this happened just after i resoldered all advised components . Please forgive too for my bad explanation as i'm not used to ask for advises on the internet and in another language other than mine. I'll do my best thou.

[Rtech]

Re: HP Monitor Mash-up

Normally these Boards give very little trouble,and most problems are caused by failure of either the wiring or the Backlights at the top of the Screen.Did you eliminate these as the problem,before re-soldering erc ???
I would also check where you have resoldered to ensure that inadvertantly you have not created a short circuit somewhere,it is easily done.
Looking at your photo it would seem that there is some heat discolouration around U502,again this is unusual for this Board,although quite common on lots of others.
After checking your soldering,and advising ref the Backlights,I suggest you diconnect J808,which supplies the Source voltage for the N channel mosfets U501 and 502,and see if your Schottky diodes D803 and D805 then still get hot !!

[Jmlcat]

Re: HP Monitor Mash-up

Well I gave it a try and even opened coil L802 but still the same . Nothing visible that can justify a short circuit and I'm out of ideas and it just got out of my range ...

[Jmlcat]

Re: HP Monitor Mash-up

Sorry guys, moving my questions to budm's thread dedicated to the monitor in question. Thank you all!