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Old 10-28-2009, 02:44 PM   #1
George Ortiz
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Default HP L1740 Lcd inverter/power board

I have four HP L1740 monitors that have failed recently. Each has the same problem. Powers up normally, displays (windows desktop) for a couple of seconds and then goes black. I have diassembled three of monitors all three inverter/power boards have blown caps. I am going to order the following caps from mouser.com:
470 uf 50V, 140-ESRL50V470-RC (XICON)
1000 uf 50V, 661-EKY500ELL102MM2 (UNITED CHEMICON).
2200 uf 25V, 647-UPW1E222MHD3 (NICHICON)
1000uf 16V, 647-UPJQC102MPD (NICHICON)
1000uf 25V, 647-UPM1E102MHD (NICHICON)

The inverter/power board p/n is T50P062.00 Rev:2 I have been trying to find any information on these boards, assembly, schematics, etc. Also this is my first attempt at repairing these monitors. If I can repair them, 2 of the 4 monitors are mine to keep. The other two are for company spares.
Hope I am on the right track in replacing these blown caps.
thanks,
George
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Old 10-28-2009, 04:27 PM   #2
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Lightbulb Re: HP L1740 Lcd inverter/power board

Welcome George!

Original caps brand, series, & dimensions (DxH in mm), please. HOw many of each value? What is max height you can go?

Pics are always a plus!

I question a couple of the choices, but I'd need to see the originals info first. The PJ is a General Purpose cap and the ESR on a few looks a touch too high.

Also, resolder the transformers at all pins and check the C5707 transistors. Any heat damage or discoloration of the board around them would make them suspect.

Toast

Last edited by Toasty; 10-28-2009 at 04:29 PM..
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Old 10-28-2009, 05:14 PM   #3
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Default Re: HP L1740 Lcd inverter/power board

All capacitors are CapXon:
470uf 25V 10mm x 9mm (3 each)
2200uf 10V 10mm x 12mm (2 each)
1000uf 25V 15mm x 12mm (1 each)
1000uf 10V 10mm x 9mm (1 each)
1000uf 6.3V 8mm x 9mm (1 each)

I think there is only 1 Transistor on here and checked for shorts, none found.
don't have digital camera right now so no pictures at the moment.
thanks.

Any recommendations on replacement caps would be very helpful.
I am going to order enough capacitors to repair the four inverter/power
boards. Also any info on who makes these invertors????

Last edited by George Ortiz; 10-28-2009 at 05:17 PM..
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Old 10-28-2009, 05:35 PM   #4
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Lightbulb Re: HP L1740 Lcd inverter/power board

Series is on the side opposite the values. Right near the temperature markings. Similar looking to this:

KF 105C -or- KM(M) 105C

KF & KM would be the series.

Toast

EDIT: Inverters are made by several. Usually marked on the board. FSP is one maker.

Last edited by Toasty; 10-28-2009 at 05:37 PM..
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Old 10-28-2009, 05:45 PM   #5
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Default Re: HP L1740 Lcd inverter/power board

Toasty all caps are KF 105 C......
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Old 10-28-2009, 08:10 PM   #6
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Default Re: HP L1740 Lcd inverter/power board

Your dimensions don't match the Capxon data sheet. If you are in the USA I suggest Digikey. All of the following match the Capxon dimensions and are in stock. They will ship the following order for under $3.00 via first class mail.

470uf 25V (3 each) P12388-ND Panasonic EEU-FM1E47 @ $.50 ea *
2200uf 10V (2 each) P12357-ND Panasonic EEU-FM1A222 @ $.76 ea
1000uf 25V (1 each) P12379-ND Panasonic EEU-FM1E102 @ $.76 ea
1000uf 10V (1 each) P12353-ND Panasonic EEU-FM1A102 @ $.50 ea
1000uf 6.3V (1 each) P12340-ND Panasonic EEU-FM0J102 @ $.37 ea

Unit quantity. There is about a 25% discount for quan. 10


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Old 10-28-2009, 08:23 PM   #7
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Default Re: HP L1740 Lcd inverter/power board

Your first cap choice, the 470@50, is 13x25mm where the original is a 10x9mm. Can you go 25mm high?

I asked back in the beginning how high can you go...?

Toast
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Old 10-28-2009, 10:16 PM   #8
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Default Re: HP L1740 Lcd inverter/power board

Quote:
Originally Posted by Toasty
Your first cap choice, the 470@50, is 13x25mm where the original is a 10x9mm. Can you go 25mm high?

I asked back in the beginning how high can you go...?

Toast
Note his 4:14 post. The original is 470 @ 25.

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Old 10-28-2009, 10:30 PM   #9
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Default Re: HP L1740 Lcd inverter/power board

READ his FIRST post.

THEN go here:
http://www.mouser.com/ProductDetail/...vOCbYUtA%3d%3d

"Dimensions: 13 mm Dia. x 25 mm L"

I WAS working on this when you posted. AGE before BEAUTY....

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Old 10-28-2009, 10:32 PM   #10
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Default Re: HP L1740 Lcd inverter/power board

Ok on the panasonic caps, but one question? Can I install caps that approximately double the voltage???? I have seen several lcd repairs on youtube and read about other repairs, that the replacement caps are double the voltage than the original caps.
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Old 10-28-2009, 10:52 PM   #11
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Default Re: HP L1740 Lcd inverter/power board

The caps don't set or change the voltage, the circuit does.
The voltage marked on a cap is the caps limit.

If you have a piece of wire that's rated for [limited to] 250v can you safely use it on 120v?
- Same idea.
.
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Old 10-29-2009, 12:08 PM   #12
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Default Re: HP L1740 Lcd inverter/power board

Quote:
Originally Posted by George Ortiz
Ok on the panasonic caps, but one question? Can I install caps that approximately double the voltage???? I have seen several lcd repairs on youtube and read about other repairs, that the replacement caps are double the voltage than the original caps.
You can, but I don't recommend it. Using higher voltage caps makes it more difficult to find replacements that will fit in the available space. Also, your higher voltage (and higher cost) cap will gradually reform itself to the lower voltage.

The original caps did not fail because the voltage was too high, they failed because the ESR (equivalent series resistance) rose as the cap aged. Eventually the capacitor overheated and popped it's top from the power it was dissipating. Panasonic FM series and similar low ESR caps from other reputable manufacturers have a much longer life expectancy.

PlainBill

Last edited by PlainBill; 10-29-2009 at 12:11 PM..
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Old 10-30-2009, 08:03 AM   #13
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Default Re: HP L1740 Lcd inverter/power board

I agree.

There is nothing -wrong- with using a higher volts caps, it's just that it makes things harder [fitting and on your wallet] and there aren't any benefits due to the higher voltage rating.

If you run a 50v cap in a 16v circuit the chemistry going on inside the cap changes the thickness of the oxide layer on the aluminum to be consistent with 16v.
[This is called reforming, as in reforming the oxide layer.]
That thickness is the primary characteristic the voltage rating is based on. When it adjusts to a thickness for 16v you no longer have a 50v cap, you have a 16v cap. If you then put the reformed to 16v cap into a 50v circuit the thinner oxide layer will allow excessive currents and overheat the cap most likely to the point of it failing quickly.

When you see an over rated cap [higher voltage than needed] the usual reason they did that is that higher voltage caps tend to be bigger [physically] and physically bigger caps [of some given grade] have lower ESR.
- They didn't go up in volts for the volts, they went up for the bigger can size.
It's the el'cheapo way to get better ESR.
The two ways usually used to get better ESR:
- Use a physically bigger cap. [The el'cheapo way]
- Use a better grade of cap.

You are much better off using a better grade than you are going to a higher voltage.
For screens Panasonic FM is an excellent choice.
In fact [for screens] Panasonic FC or Nichicon PW are better grades than what was originally in there maybe 80-90% of the time.
But if you can't find the specs for the old caps to be sure FC or PW are good enough replacements then defaulting up to Panasonic FM or better is the way to go.
Oddly, Panasonic FM is often less expensive than FC or PW.

.
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Old 10-30-2009, 05:03 PM   #14
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Default Re: HP L1740 Lcd inverter/power board

thanks everybody for you input and help. I am going to order from digikey
enough capacitors to repair all four monitors and then have enough in hand to repair another two if they (most likely will) fail. Thanks again for your help!!!!!!!
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Old 11-02-2009, 08:59 PM   #15
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Default Re: HP L1740 Lcd inverter/power board

All,
Finally was able to get a picture of one of the inverter/power supplies.
George
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File Type: jpg DSC00188 (1536 x 1152).jpg (345.1 KB, 262 views)
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Old 11-03-2009, 03:54 AM   #16
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Default Re: HP L1740 Lcd inverter/power board

Quote:
Originally Posted by George Ortiz
All,
Finally was able to get a picture of one of the inverter/power supplies.
George
Just a suggestion
It seems that you may have a problems on the back of this board judging by those burn marks, (hope I am wrong)
Post a picture of the back of this board (without flash please if possible)
BTW Your board is a Philipps I believe and dmbj is a Benq, this monitor must use both boards
Bob
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Old 11-03-2009, 05:16 PM   #17
George Ortiz
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Default Re: HP L1740 Lcd inverter/power board

Bobdee,
would you happen to have any techincal information on this Philips inverter/power supply board or where I could get it. Real hard to find.
Thanks,
George
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Old 11-03-2009, 06:11 PM   #18
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Default Re: HP L1740 Lcd inverter/power board

Quote:
Originally Posted by George Ortiz
Bobdee,
would you happen to have any techincal information on this Philips inverter/power supply board or where I could get it. Real hard to find.
Thanks,
George
Afraid not, sorry this board is new to me
Suggested a picture of back of board because it sounds like faulty inverter or CCFLs, and the dark heat area is probably the mosfets the members helping you will need to see the other side
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Old 11-03-2009, 07:32 PM   #19
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Default Re: HP L1740 Lcd inverter/power board

Quote:
Originally Posted by Bobdee
Afraid not, sorry this board is new to me
Suggested a picture of back of board because it sounds like faulty inverter or CCFLs, and the dark heat area is probably the mosfets the members helping you will need to see the other side
Right, the discoloration is extreme, but could be nothing more than the result of running for an extended time with failing caps. Unless the traces have actually lifted from the substrate it is possible to replace any shorted transistors.

PlainBill
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Old 11-04-2009, 09:09 AM   #20
George Ortiz
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Default Re: HP L1740 Lcd inverter/power board

PlainBill,
I checked on the other board that I have at home. This is my prototype repair board.
It has the same discoloration as the board I have here at work (the one photograhed here). There is another board with the same burn marks. All have blown caps.
Looks like running for extended time with failing caps. There are no circuit board tracks lifted on the other side of the boards.

Last edited by George Ortiz; 11-04-2009 at 09:12 AM..
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