HP 2509m won't turn on, no power to ON/OFF LED

[budm]

Re: HP 2509m won't turn on, no power to ON/OFF LED

Look at the Gate capacitance value also, the larger the capacitance the longer time it will need to be discharge to make sure the MOSFET will be off before the next drive cycle begin. You want it to be the same or less.
You want the same or lower Rds.
Gate drive voltage should be the same or can be lower.
90 mOhm to 240mOhm is a big number, almost 3 time as much, if you force the same amount of current then you calculate how much more power it has to dissipate.

[Freezer]

Re: HP 2509m won't turn on, no power to ON/OFF LED

Look at the Gate capacitance value also, the larger the capacitance the longer time it will need to be discharge to make sure the MOSFET will be off before the next drive cycle begin. You want it to be the same or less.
You want the same or lower Rds.
Gate drive voltage should be the same or can be lower.
90 mOhm to 240mOhm is a big number, almost 3 time as much, if you force the same amount of current then you calculate how much more power it has to dissipate.

Thanks for the quick reply. Applying your info to my digikey searches I get the following for the N-channel MOSFET:

Original P5506BDG:
V(br)dss = 60V
Rds(on) = 55mohms
Id = 22A
Vgs = +/-20V
Pd = 50W
Vgs(th) = min=1V, max=2.5V
Ciss=587pF

STD16NF06LT4:
V(br)dss = 60V
Rds(on) = 70mohms
Id = 24A
Vgs = +/-18V
Pd = 40W
Vgs(th) = min=1V, max=? (datasheet does not specify)
Ciss=370pF

STD20NF06LT4:
V(br)dss = 60V
Rds(on) = 40mohms
Id = 24A
Vgs = +/-18V
Pd = 60W
Vgs(th) = min=1V, max=2.5V
Ciss=660pF

The STD20NF06LT4 appears better in all categories except gate capacitance which is 12% higher. The STD16NF06LT4 on the other hand has worse resistance and power dissipation, but better gate capacitance. These are the only 2 options I'm able to find on digikey.


As for the P-channel MOSFET:

Original P9006EDG:
V(br)dss = -60V
Rds(on) = 90mohms
Id = 8A
Vgs = +/-20V
Pd = 28W
Vgs(th) = min=-1V, max=-3V
Ciss=760pF

SPD09P06PL G:
V(br)dss = -60V
Rds(on) = 250mohms
Id = 9.7A
Vgs = +/-20V
Pd = 42W
Vgs(th) = min=-1V, max=-2V
Ciss=450pF

STD10P6F6:
V(br)dss = -60V
Rds(on) = 160mohms
Id = 10A
Vgs = +/-20V
Pd = 35W
Vgs(th) = min=-2V, max=-4V
Ciss=340pF

Both of these are similar in that that have higher resistance, and slightly different gate/source threshold voltage. As for the resistance, I honestly wonder if the original part is mislabeled, or if the manufacturer was overly optimistic. No MOSFETs of similar specs on digikey have a resistance anywhere near the 90mohms claimed. So for me, the big question is gate/source threshold voltage. Does this matter or can it vary from the original by a volt or two?


As of now I think I'm leaning towards the STD16NF06LT4 and the STD10P6F6. But I'm still open to suggestions. The good news is, the monitor was free and I'm willing to experiment with it. So if the MOSFETs I select end up damaging the monitor further, I won't care. I'm hoping to use this monitor as a test bed to find the right MOSFETs for future people repairing this monitor.

[budm]

Re: HP 2509m won't turn on, no power to ON/OFF LED

"The STD20NF06LT4 appears better" That is close enough.
Please read this:


The P-CHANNEL is not going to be easy.

[Freezer]

Re: HP 2509m won't turn on, no power to ON/OFF LED

A good friend of mine is an electrical engineer so I asked his input. He said if I could tell him the part number of the driver IC he could analyze the circuit and find MOSFETs that fit the circuit, which would be easier than trying to find a replacement for the existing MOSFETs. Unfortunately, I'm unable to find a datasheet for the driver IC (I don't have the IC part number in with me, but I believe it's in this thread). But he did his best to find replacement MOSFETs.

For the N-channel he selected the STD20NF06LT4, which is the same part I was looking at (I didn't tell him what I'd found ahead of time, he researched this with a fresh pair of eyes).

And for the troublesome P-channel he found IRLR9343PBF. Here are the specs compared to the original P9006EDG:

Original P9006EDG / replacement IRLR9343PBF
V(br)dss = -60V / -55V
Rds(on) = 90mohms / 105mohms
Id = 8A / 20A
Vgs = both +/-20V
Pd = 28W / 79W
Vgs(th) = both min=-1V
Ciss = 760pF / 660pF

This looks like a good replacement to me. The voltage is slightly lower, but unless the circuit is driving this MOSFET within 5V of its limit, that shouldn't be a problem. Also, the Rds(on) is slightly higher, but compared to the other options I was finding at 3 times higher, this is a very close match.

In the next few days I'm going to order a STD20NF06LT4 and IRLR9343PBF. With any luck in a week or two I'll report back how this repair goes.

[selldoor]

Re: HP 2509m won't turn on, no power to ON/OFF LED

Perhaps when you get them in set it up with a 75w filament bulb in the mains input. If there are other problems on the board this might keep safe your new parts.
Google- Dim Bulb Test.

[Freezer]

Re: HP 2509m won't turn on, no power to ON/OFF LED

It's been several weeks, but I finally got time to work on this monitor. The short answer is - the repair was successful! After opening the monitor I first performed a visual inspection and tested the ESR of the caps - no problems found. So I desoldered the little daughter board to test the problematic MOSFETs and diode. Testing in circuit I'm pretty sure the diode and N-channel MOSFET were bad. After desoldering and retesting, the diode and N-channel were most definitely bad. The P-channel was probably good, but I went ahead and replaced it anyway.

As for removal, since we're talking about surface mount stuff it can be a little trickier. For the MOSFETs I put my iron on one leg and once the solder was melted I used side cutters to clip the leg at the base of the MOSFET. I then removed the second leg, after which I held my iron on the tab, and once that was melted I could slide the component off, all without damaging the pads. The diode ended up being easy. I put my iron on one side and the heat transferred through the diode and melted the other side so it just lifted right off. Below are the original and replacement parts I used:

N-Channel MOSFET:
Original: P5506BDG
New: STD20NF06LT4

P-Channel MOSFET:
Original: P9006EDG
New: IRLR9343PBF

Diode:
Original: SR26
New: SS26


After repairing the monitor I wasn't sure if it would work. A lot of people who've repaired these monitors have reported that after repair their CCFLs were bad. Fortunately for me the only problem was the MOSFETs and diode. I've run this monitor for 10+ hours continuously since repair and everything looks great. So for anyone else trying to repair this monitor, the replacement MOSFETs I listed above appear to be well suited replacements.


Unfortunately I didn't take any pictures of this repair, but I did produce a video. I hope this helps someone repair the same or similar model.

[selldoor]

Re: HP 2509m won't turn on, no power to ON/OFF LED

Well done - nice repair

[withalligators]

Re: HP 2509m won't turn on, no power to ON/OFF LED

Ugh, mine's buzzing now. Going to look into replacing the P and N channel mosfets with your upgrades before the bulbs go. Thanks for the diligence Freezer.

[bmwed]

Re: HP 2509m won't turn on, no power to ON/OFF LED

Thanks to all for the great info. I managed to change the two transistors and the diode. This was my first time working on a SMT board, so my soldering wasn't perfect. The monitor worked for about 2 minutes and then the display went black. I checked the diode and it was open both ways, and the transistors also were bad.
Is there something I missed, did I possibly overheat the components when soldering. Or is there a faulty component upstream that I should have checked.
Thanks
Ed

[Davi.p]

Re: HP 2509m won't turn on, no power to ON/OFF LED

Wich part have you put instead of the originals? I would like to say that for me the half screen backlight sympton is not because old ccfl, in fact in those threads owners had the fault a bit after warrany end, is the solderig job that is not good so if you inspect those and find that the terminals of the lamps are good enough to try resolder them by new (with good solder) you can save them, a ccfl is old only when at the ends are black. Said this is not so good to assign all guilts to HP because as many other brands produce monitors assembling panels by other vendors, it's not easy to produce lcd technology.. I want also to say a trick that i discovered the first time i have changed ccfl without breaking any lamp, it's impossible to slide the silicone terminal cover through the cables because silicon on silicon or silicon on rubber makes too much grip, just slide them very slowly through the lamps letting to bent a little, holding lamps near the end, you can help also a little if you want by wet the lamps with water or water+soap. BYE.

[bmwed]

Re: HP 2509m won't turn on, no power to ON/OFF LED

[QUOTE=Davi.p;591264]Wich part have you put instead of the originals? I would like to say that for me the half screen backlight sympton is not because old ccfl,

I replaced the originals with:
N-Channel MOSFET: STD20NF06LT4
P-Channel MOSFET: IRLR9343PBF
Diode: SS26
Didn't touch the ccfl tubes, just changed those components. Monitor worked perfectly for about 2 minutes, then screen went black. Diode was open both ways and transistors were bad also. Thinking it may be something upstream causing this. My soldering wasn't that bad.
Ed

[pestalent1]

Re: HP 2509m won't turn on, no power to ON/OFF LED

I know this post is way old. The same thing happened to me as "bmwed". Did you ever figure it out ?
Thanks