Dell 2209W - no power at all - stripped down but can't see anything obvious

[Batz]

Hi all, first post so be gentle!

I got a lovely Dell 2209W off eBay and 6 weeks later while I am in the middle of something on the computer it goes black and the LED in the power switch has gone out. I hoped it was a fuse in the power lead but I replaced this to a known working one and still nothing. I can hear a faint crackling as I push the lead into the socket on the back of the screen as if power is being drawn by the monitor to some extent. Anyway, no amount of lead wiggling can coerce the screen to be anything but completely dead so I google a bit and a few days later I manage to open it up and strip it down so I can see the PCBs. I also read a few forum posts here on similar topics and try to find any fuse that might be blown or any capacitors that look bad but I can't see anything obviously broken.

So I took some pictures and have attached them here to see if anyone has any ideas of what I might do next.

DSCF3740 to DSCF3743 are the main board just rotated in case anything is obscured by shadows. DSCF3744 is the back of this PCB.

DSCF3745 to DSCF3747 is a secondary board.

DSCF3748 is the back of the monitor with the above PCBs removed. The main board goes in the middle and the secondary to the right.

All connectors are into the main board except USB which has a tiny PCB under the silver 'hood' to the left in photo DSCF3748. I haven't bothered taking a picture of this but I took a look at it and it also looks fine.

I have a multimeter but haven't measured anything as I wouldn't know where to start and I don't want to blow anything up!

I have also examined the little PCB that goes behind the push buttons. It all looks in order.

I really hope someone can help me here because this screen was over £120 (GBP) which is I guess around USD$200.

Thanks
Ian

[jetadm123]

I would suggest measuring the voltage across the large 120uf 450V cap. Assuming your outlet voltage is 220VAC, then you should see approx 220V x 1.414 = 311 VDC across that cap.

[Jasgriff]

As jet recommends above....

I would also check the fuses whilst your at it they are in positions

F850
F851
F852
F853

From what I can make out.

[Batz]

Thanks for the super speedy replies. I'll test these and come back to you guys.

[Jasgriff]

Make sure you test the fuses with the power off

[selldoor]

Hi yes try as jetadm123 suggests.
I usually give newbies a bit more instruction:

For this test you need to just connect the power supply to the mains - no other boards - make sure the board isnt touching another board and that you are not working on a conductive surface.
ASK if unsure about anything - we have all been there.

These are high voltages so great care needed
Set your meter to 600vDC and put the black (negative) probe on the Negative leg of the the capacitor. Put the red (positive) probe on the positive leg of the capacitor. Do not hold the probes too near to the metal points.
Remember heat sinks can carry a voltage that will give you a nasty jolt.
If you have not used your meter for some time practice a bit on 9v battery 1.2v 1.5v a couple together etc so you get used to holding the probes and looking at the meter.

I notice there are 4 yes at least 4 fuses on the board. If you like you can practice with your meter on those.
Simple rule here Measure voltages = power on
Measure Resistance = power off ( for 5 mins)
Set meter on Ohms 200 if you can and with the power off just measure the fuses and post your findings - should be the same as touching the probes together. The fuses I have spotted are two red ones at the top left of the board (looking at your picture) and two at the bottom- One on right of power socket looks the same sort as the two at the top. The other is on the left of the power socket and is a red vertical cylinder shape. The board will have marking near them with F in it.


EDIT - Im just going to have to find shorter answers. or type a lot faster

[Batz]

Cool, thanks for the extra help. I had actually already gone away and done the work but I am not a total newbie as I did Electronics O level at school 25+ years ago and I know the basics to not blow my fingers off

So anyway this is what I did, I removed the main board from the case and all connectors. Measured all the fuses. Switched off at the wall then plugged it in. Measured the capacitor. Switched off at the wall.

All fuses are measuring close to zero resistance.

The big capacitor is varying between 390V and 405V. I am in the UK so the wall should be between 220V and 240V I did try to measure across the kettle lead but didn't get anything meaningful, probably me prodding the wrong bits. Edit: I just remembered it will be AC not DC and I didn't switch over!! Edit again: I just realised that I think I first tried to measure the voltage on the big capacitor before turning the dial from Ohms to Volts and I've just checked the fuse in the back of the multimeter next to the batteries and it is blown. I am obviously more of a noob than I thought .... oops. Down to Maplin tomorrow then ...

I measured a few spots on the reverse of the board where it states GND and +12V or +24V or +5V and these seem to be varying all over the place. Maybe it's my measuring but I don't think so.

I am not sure about using my meter other than dial it to V to do Voltages or Ohms symbol for resistances! And of course put the probes in the right sockets for each job. I have attached a photo of it in case it helps.

[Jasgriff]

Just noticed that you also have some Fuse resistors on that board too I think I could see 3 of them they would be worth a check.

You say that you measured some other voltages can you give us the actual readings of +12 +24 and + 5v.

[Batz]

Since I blew the fuse I can't get a continuity test to work. If I hold the probes together then the scale just wanders. I have done a bit of google-reading to refresh my memory on how to use a multi meter and I'll get a replacement fuse for the meter tomorrow and test those fuse resistors, I presume they are the components with references starting FR ?

[Jasgriff]

Yeah they start with FR. Does the resistance setting work? if so use that to test them.

[retiredcaps]

Originally Posted by Batz

Hi all, first post so be gentle!

Well lit, clear focused non inline pictures, punctuation, paragraphs, a picture of your multimeter, sigh I wish more first posts were this good.

Did I mention a picture of the multimeter!!!!

[jetadm123]

Originally Posted by retiredcaps

Did I mention a picture of the multimeter!!!!

Actually, the photo is on post #7

[Jasgriff]

Lol,

I was going to mention that you would love the fact he has included a pic of his multimeter.

I think Retired was praising such a good first post and the fact that he did included his meter.

[retiredcaps]

And now some value add. Service manual with a schematic of the power board on page 38.

http://elektrotanya.com/dell_e2209wc.pdf/download.html

Once you get your multimeter fixed, the schematic will help.

[Batz]

Thanks for all the kind comments, I made sure I got decent photos, it was great that I happened to have time during the brief Edinburgh summer which this year seemed to fall for one week in March, it's now sleeting down outside ...

Great work getting the service manual, I did some googling for something like this but couldn't find anything.

I'll post back once I have fixed the meter which may not be today as I am looking after kids on Easter break and one of them is 'wuffing her custard' every so often (as my sister would describe it! AKA being sick).

[Batz]

I can't find a download link on that page to actually download that service manual. Did you manage to get it downloaded?

[selldoor]

Its a little bit tricky - you have to switch off any stuff like ad blockers or allow
them on that site then it can take up to a minute for the link to appear.
Its in black at the bottom right hand side - small writing tho - not the big green ones.

[Batz]

OK, got that now, thanks for the tip, I had to turn off AdBlock.

Having a quick skim through the manual this is not quite the same as my monitor, the main board shown in the manual is quite different to mine. The pictures in the manual on page 32 show two boards where mine has one larger board. My monitor is actually a 2209WAf according to the serial number panel. Built in 2010.

Nevertheless it should be helpful as there are probably similar components and build methods.

[jetadm123]

Originally Posted by Batz

OK, got that now, thanks for the tip, I had to turn off AdBlock.

Having a quick skim through the manual this is not quite the same as my monitor, the main board shown in the manual is quite different to mine. The pictures in the manual on page 32 show two boards where mine has one larger board. My monitor is actually a 2209WAf according to the serial number panel. Built in 2010.

Nevertheless it should be helpful as there are probably similar components and build methods.

Yes, I also took a quick look at the schematic and it is different from yours as it has it's power supply and logic boards separate. Whereas on yours, as you pointed out, everything is intergrated on one board. Just goes to show you how quicky they change power supplies on what essentially is the same model monitor.

[Batz]

I got a pack of fuses for the multimeter from Maplin and it seems to be working fine again.

OK, things don't look too good for this board. All the fuses and fuse-resistors are registering continuity (i.e. near zero ohms).

The voltages are really hard to measure because the multimeter is auto ranging and although it has an auto/manual button I can't figure out how to work it.

Anyway here are the readings, they are all rapidly wandering up and down within a period of a second or so:

+5V near C964 between 0 and 1 volt (0 and 1000mV)
+24V near F851 between 16 and 21 volts
+12V near F853 between 600mV and 1.6V

The big capacitor registers between 393V and 402V

Input voltage measures 244V AC

Hope this helps!