Dell 2407WFPb Monitor - Bad Cap

[selldoor]

Originally Posted by sabretooth

I checked F701. It seems OK! It's also not like any fuse I've ever seen before. But it checked out.

No, as I said I had not seen one before but there was a phillips tv with some in a day or two back

Unfortunately I've got no idea how to determine resistor wattage based on size. It's approx 4mm x 10mm, though. Googling "4x10mm resistor" has come up with a bunch of hits suggesting 1 watt.

Ive looked on digikey - yes 1 watt is most likely

The silver line of solder I think you're referring to - the goop that used to
hold down the original capacitor? I'm not seeing any lines of solder.

Good- couldnt tell from pic what it was - it was just something odd.

[sabretooth]

Alrighty. I think I've got everything I need to know. Time to make the orders - having to turn to eBay for the resistors but everything else I can get from a few local reputable stores. Hopefully this ends with a working monitor and I can stop taking up a disproportionate amount of space in this thread!

[sabretooth]

Originally Posted by sirzur

I have looked at it through a magnifying glass with a bright LED light on the surface and I can't see any dot I can only assume that pin 1 is the bottom left when the words are the right side up

I must have bought the same component - no markings whatsoever as to what pin is supposed to be pin 1.

[selldoor]

Originally Posted by sirzur

I finally went by the bevel. Looked up the dimension of the SO-8 package and wikipedia showed the bevel. Pin 1 is on the bevel side, on the left

Does yours have the bevel?

[sabretooth]

I thought I was clever by doing a search on the forum and finding his post - shame I wasn't resourceful enough to find the followup It indeed does have a bevel on one side. Thanks.

[sabretooth]

Argh, well this has come to a premature end. When I was removing one of the ICs, I must have yanked out one of the lines onto which the IC solders. Damned if I can find where it comes from.

[selldoor]

If you post a good picture of the damage zone we may be able to suggest
a fix.

[sabretooth]

Hopefully this is good enough, then!

I've already tried scratching around to find the trace but haven't tried very hard and didn't want to push it in deeper or make fixing more difficult.

[selldoor]

Looks fixable - I am just going off for a week (very inconvenient!) others should be able to advise. Try and clean the area up with isopropyl alcohol on cottonbud or soft brush
Probably Not all the pins need attachment see if you can find a datasheet for the chip.

[Jasgriff]

I agree with selldoor... Very inconvenient that he is having a week off!

Do you have any isopropyl alcohol? dont scratch it anymore just get hold of some of that stuff and it will clear the majority of it up. Then get us another pic and we can help work out what goes where.

[dawm123]

Originally Posted by WillyBobz

Thank's for all the information NZROSSI, I have just looked on the website....wow it looks quite complicated! Can you give me any step by step instructions as to how to order, I will use the same agent that you used. Any help/advice GREATLY APPRECIATED!!!!
Regards
WillyBobz

Also need help.I smalltao point of view in things, but do not know how to do this?

[sabretooth]

Alright, busy times but got some time to clean up the circuit board and take a photo.

I'm pretty sure I've ruined it! See attached.

[WillyBobz]

Hi Sabretooth,
Check out this link below, it is for a Polish forum, use google translate, it also has the Diagram for L651, hope that this may help you.
Good Luck!


http://obrazki.elektroda.pl/1950185900_1304529310.jpg

[selldoor]

Originally Posted by WillyBobz

Hi Sabretooth,
Check out this link below, it is for a Polish forum, use google translate, it also has the Diagram for L651, hope that this may help you.
Good Luck!


http://obrazki.elektroda.pl/1950185900_1304529310.jpg

I am not so sure-Willtbobz, what was the main link to this.
The components we do know are D605 on pin5 (not on pic) A 10k resistor on pin1 (could be on pic but not labelled C613 on pin 6 (not on pic)
Similarly we have R617 R627 R622 R609 Q602 not mentioned on pic.
perhaps they only have topside components labelled.

[selldoor]

Right - Help required from circuit experts - I attach a pic - I have guessed that the IC in question is a NCP1200A (got confused in the threads) Most of the connections seem obvious but struggling with where pin 8 goes. Sabretooth can you see the hole/pin I have dotted the yellow to - what is on the other side of the board at that point. Can you do a close up of the area.
Team -feel free to comment this is a suggestion only and we dont want to cause further damage.

[budm]

If I am correct, that HV pin is the kick start power input from the main DC supply through a bunch of resistors connected in series to drop the 325 Vdc from the main cap down to about 12~18vdc to start the SMPS, once it started, the power supply circuit inside the SMPS will switch from the HV pin to the VCC pin which is generated by the extra winding off the transformer.
I have the 2407WFPB at home that I need to work on, so which board is this I need to look at?

[selldoor]

Power supply back – board number is 4H.L2K02.A01 position marked on attached

[soumen1]

Originally Posted by soumen1

I have replaced the unknown zener with a 6.8V 5W zener. [...] My only remaining question is, should I continue like this with an external 5V power supply, or should I try to replace the hexfet and inductor back in the board. It would be nice to get back to one power supply. The danger is, if the gate control circuit was damaged, the zener and hexfet will do fireworks again, and this time I may not be lucky and downstream components may fry.

Update: I tried replacing the hexfet, and thanks to the 5W 6.8V zener I earlier connected across the load, my display board (the one with the Genesis chip) did not fry. The hexfet gate control is clearly kaput as well, as the supposed 5V drain rose to about 7 volts and the zener got hot (but survived). I turned off the monitor hastily and returned to an external bypass 5V power supply to the display board.

Without a schematic and test voltages, it's very hard to debug the gate control of the hexfet. So my plan is to install a Murata OKI-T/3-W40P-C POL buck DC/DC converter from the 19V source to the required 5V drain, bypassing the on-board converter completely like I am doing now, but drawing from the 19V rail on the internal SMPS board. BTW, I also added the 27V zener in parallel with a 30V MOV on the 19V rail (after the 5A slow blow fuse) for added safety in future.

http://www.murata-ps.com/data/power/oki-t3-w40.pdf

[WillyBobz]

Originally Posted by selldoor

Right - Help required from circuit experts - I attach a pic - I have guessed that the IC in question is a NCP1200A (got confused in the threads) Most of the connections seem obvious but struggling with where pin 8 goes. Sabretooth can you see the hole/pin I have dotted the yellow to - what is on the other side of the board at that point. Can you do a close up of the area.
Team -feel free to comment this is a suggestion only and we dont want to cause further damage.

Pin 8 connects to R603 on other side of board as in the Diagram on the link in my previous response.

I have checked this against a power supply board that I have on the bench.
Sorry unable to take a decent picture (close up)

[selldoor]

Thats Great Willybobz - I forgot there is a high def pic earlier in the post.
I think we just need sabretooth to test what pads he has got for continuity to the next joint then he can try and fit it. Any without continuity will have to be wired. Perhaps he can put a snipped cap leg into the "through" and a
small wire from that to pin 8 rather than just a solder blob. Anyone any other ideas.