Dell 2007fpb no power

[duceolsen]

Monitor does not light up anything, acts as though no power to device.

Opened up and was able to get a positive 20v and that is it. I believe I should also be getting a 12v or at least 5v as well. No apparent bad parts that I can see, does anybody have a good place where I can request a schematic or anything for this monitor?

[Dgtech]

Re: Dell 2007fpb no power

How are the fuses? How are the caps? Posting some pictures of the boards in question would be a good start.

[el3ctroded]

Re: Dell 2007fpb no power

Pictures of top and bottom of all PCBs please.

[severach]

Re: Dell 2007fpb no power

Some power supplies only output a single voltage and each board uses 78xx compatible linear regulators to produce whatever they need. Pictures of the boards would help us decide how many voltage outputs there should be.

[duceolsen]

Re: Dell 2007fpb no power

So while trying to do further testing I accidentally shorted out the board and blew the fuse, after replacing the fuse resistor 613 smoked on me. Of course I did not take pictures before doing all this so I have no idea the correct rating resistor 613 is supposed to be.

[momaka]

Re: Dell 2007fpb no power

It seems the PSU board has one voltage rail only as severach suggested, so the fact that you got a single voltage reading means it was working prior to the short.

Any chance you can get higher resolution pictures of the power supply board? I'm having a hard time locating R613. Might be able to tell what it should be with better pictures.
Also, how did you short the board (and more precisely, which one)?

[retiredcaps]

Re: Dell 2007fpb no power

I take my boards to the window when it is sunny and use macro mode. It produces super clear legible photos. No tripod needed either.

Might be able to tell what it should be with better pictures.

[duceolsen]

Re: Dell 2007fpb no power

This just makes me mad, Ive discovered that the short also blew out the large mosfet which is what caused the resistor to smoke, I had circled the resistor in red in the bottom image.
While I was figuring out why on earth the resistor smoked the bridge rectifier also went bad on me. lol I am about ready to toss this whole monitor.

So in other words my screwing around caused the good powersupply to go kaput and the problem was likely elesewhere.

[momaka]

Re: Dell 2007fpb no power

Looks like R613 might have something to do with the voltage supply on the 8-pin IC. Any chance you can read the numbers on that small 8-pin IC?
You'll also need to replace the bridge rectifier. Just looks up the number that is written on it, then google it. Should be something rated for close to 2-4A, 600v. Do the same with the mosfet. If you're having trouble finding replacements for these, post their numbers here.
Start checking the rest of the components on the primary side. All resistors should read close to or lower than their stated value. If a resistors reads much higher than what it's rated for, it's probably bad. Also check TR601, D602, and R615(?) as those are important.

lol I am about ready to toss this whole monitor.

Don't worry. In worst case scenario you can always wire an external power supply. Something along the lines of 12v, 4-6A should be good enough.

[duceolsen]

Re: Dell 2007fpb no power

Alright I have found a new rectifier KBL06-E4/51 which is the closest replacement I could find for GSIB4A60.
The Mosfet I am having a hard time finding a data sheet on, the part number is 2SK3548.

[duceolsen]

Re: Dell 2007fpb no power

I take that back, the gsib4a60 the leads are 7.7mm apart, the closest I can find then is GBL06-E3/45 and the leads are 5.3mm apart, guess I can bend them some.

[el3ctroded]

Re: Dell 2007fpb no power

The only thing I saw said the 2sk3548 was 900V 10A likely a N-ch FET, but it's not in Toshiba's part list...

Are you absolutely sure you got the number correct?

[duceolsen]

Re: Dell 2007fpb no power

Yes the number is correct, the closest thing to the number I can find is 2sk3547 which is some n channel smd, I need a through hole.
I'll admit I know next to nothing about mosfets, it is the fellow circled red in the attached image, I'll try to get an image showing all the text on the chip.

[duceolsen]

Re: Dell 2007fpb no power

Here is the mosfet I need a replacement of. Can someone help me?

[momaka]

Re: Dell 2007fpb no power

I've tried looking on Google, but so far all websites I visited seem to only re-direct to PDFs for 2sk3547 and similar. Hopefully someone with more experience will see this thread and help you choose a replacement FET. I think the specs that el3ctroded mentioned above sound reasonable.

As far as the bridge rectifier - I looked at the GBU and GBJ series on Digikey, and most come with 5.3mm spacing only. Those that come with 7.7mm have the (+) leg with ~10mm spacing. Bending the leads should be okay though. If the heatsink becomes a problem because of this, just remove it as it's not really needed. A 4 Amp bridge rectifier is more than adequate for this monitor and won't produce much heat.

Also, have you checked the other components I mentioned, particularly that small 8-pin IC (the PWM controller)? Basically, get the data sheet for it, see what pins are Ground and Vin (supply voltage), then check for continuity between them. If there's short circuit between Ground and Vin, the PWM IC may also be bad.

[ecking767]

Re: Dell 2007fpb no power

The picture help a lot, The manufacturer logo is Fuji Electric Here is a link to there MOSFET they have in production. But I can't find anything on the 2SK3548. Maybe give them a call.

http://www.fujielectric.com/device/s...ets/index.html

ecking767

[duceolsen]

Re: Dell 2007fpb no power

8pin ic is 200A6. I found the data sheet on it relatively easily. Do I need to remove it to test it? What is the correct way to test it?
Which is the Vin? On the board there is zero resistance between pin 4grnd and 6Vcc.

I found the correct rating of r613 = 200ohm fellow on ebay had one so I asked him to take picture of it for me.

I contacted a distributor of Fuji Electric on the mosfet, they have yet to get back to me.

[momaka]

Re: Dell 2007fpb no power

8pin ic is 200A6. I found the data sheet on it relatively easily. Do I need to remove it to test it? What is the correct way to test it?
Which is the Vin? On the board there is zero resistance between pin 4grnd and 6Vcc.

I think the actual number for the IC is NCP1200 or NCP1200A, and 200A6 just tells what frequency it's operating at (in this case 60KHz).

Anyways, I'm not sure if you should be getting zero resistance between pin 4 (ground) and pin 6 (Vcc). According to the data sheet, pin 6 should actually be connected to a 10uF cap. Now I tried tracing the circuit to that pin, and it seems that pin 2 on the transformer (from top to bottom, first picture with the solder side of the PCB) supplies it with current. It looks like current comes from pin 2 on the transformer, goes through L612, gets rectified through D602, charges C606 (likely the aforementioned 10uF cap from the data sheet), continues through JR4, then JW4, and then flows into pin 6 (please verify that I traced this right, though). If that's correct, then you shouldn't be getting a short circuit. Remove one side of JW4, then measure resistance again between pins 4 and 6 on the IC. If there's no short circuit any more, check D602.
Also, it looks like the main supply current for the IC comes from pin 8 (HV). So, see what resistance you get between pin 4 and pin 8 as well. For this one, I'm sure it shouldn't be a short circuit.

Glad you found the value of R613. Just as a check, though, what are the values on resistors R609 and R608? I think they should be pretty high (a few MOhms?) because it seems that one side of R613 is connected to negative.

Hope you get a reply from Fuji so that we can get this thing fixed. Meanwhile, check the rest of the resistors and diodes in the circuit. You don't need to unsolder anything. If you get a suspicious measurement, ask here.

[duceolsen]

Re: Dell 2007fpb no power

Just received the data sheet on the chip I need, discontinued of course. Got it straight from Fuji Electronics, any help finding a replacement?
thanks

[momaka]

Re: Dell 2007fpb no power

Well, I'm no expert at all when it comes to transistor replacement, but maybe these will work? The specs sure look very close.
2SK2968
STW11NK90Z
STW12NK90Z
You can find them on Digikey, but they are all $4-5.