Dell 2408wfpb

[knoxrebel]

Dell 2408wfpb shows no signs of power. No lights on power button, screen backlight doesn't fire.

I have tested power coming into the board. Main filter cap rated at 150Uf @450 tests at 140 ~ 1.4X120v. IC601, which i assume is smps has voltage going to VCC it and is stable. I cant find a schematic to show what the output voltages should be to the video board. Any suggestions?


Also, sorry for the blurry pictures.

[selldoor]

Re: Dell 2408wfpb

Picture 1 top right corner is an orange torpedo - is it a fuse - can you test it?
There is another on on pic 3 a white rectangle right hand side next to the cap.

[jetadm123]

Re: Dell 2408wfpb

If you're reading 140VDC across the main cap, that's way too low. 120VAC x 1.414 = 170VDC. Have you tried checking the AC voltage at your outlet? It should be ~ 115-120VAC. Be careful, as it's high voltage.

[selldoor]

Re: Dell 2408wfpb

what the output voltages should be to the video board. Any suggestions?
I can see some faint writing on the back of the board - where the sockets are is that not the voltages?

[knoxrebel]

Re: Dell 2408wfpb

Tested both fuses, they test good. and voltage coming into power board is 120

[budm]

Re: Dell 2408wfpb

I agree with jetadm123, 120Vac input and you only getting 140Vdc at the main DC filter cap. Try measuring a new 1.5V batteries and see what you get, if it is OK, then put the meter in AC mode and measure the AC ripple on that main DC cap and tell us the reading.
By the way, this power supply has PFC circuits, so when the monitor is on the voltage on that big cap should be about 400Vdc.

http://s807.photobucket.com/albums/y...cpZZ1QQtppZZ20

[knoxrebel]

Re: Dell 2408wfpb

.....Also use working equipment, 1st meter was an el cheapo that was bad. I measure 165 across main filter. Ac with correct polarity on cap measures 370v.

[budm]

Re: Dell 2408wfpb

OK, when the unit is off, you should have about 165Vdc and when you turn on, it should have about 400Vdc as the PFC circuits kick in. That is what you are getting?

[knoxrebel]

Re: Dell 2408wfpb

Unit never powers on, and the writing near the connector are not voltages.

[budm]

Re: Dell 2408wfpb

What I am trying to find out if that voltage on the that cap goes up to 400Vdc or not when you hit the power switch, that will tell me if the PS_ON circuit is working or not, the Monitor may show dead screen, but the PS_ON may be working.

[knoxrebel]

Re: Dell 2408wfpb

No when I hit the power button, voltage does not change.

[budm]

Re: Dell 2408wfpb

I will see if I still have the 2408 at the recycle place to do some voltage readings.

[knoxrebel]

Re: Dell 2408wfpb

I tested the caps in parallel with an esr meter and they all test within spec. Are you able to test caps in parallel/circuit like this, or do you have to remove a leg because they are in parallel?

[selldoor]

Re: Dell 2408wfpb

Hi - What voltages do you get on the connector to the main board?.
Measure with meter on 200v DC to start then reduce if none are over 20v for more accuracy - use a ground screw for black probe. All boards should be connected for the test


Can you quote the board numbers- both boards- cant read them

Was the writing anything useful BLON PSON PWR and so on that might give us a clue.

[budm]

Re: Dell 2408wfpb

Always check them outside the circuits since it can have other components (resistors, capacitors, SEMI conductors) in parallel with the cap you are checking.

[retiredcaps]

Re: Dell 2408wfpb

1st meter was an el cheapo that was bad.

Bad isn't the word I would use to describe it. Dangerous is more accurate when the readings are that far off.

[knoxrebel]

Re: Dell 2408wfpb

Bad as in not working properly, like the focus on my point and shoot camera. Let me know if you need certain component numbers. Patiently waiting for those voltages.

[jetadm123]

Re: Dell 2408wfpb

I recommend you follow selldoor's suggestion in post #14 and measure the connector voltages. There's a 5V standby voltage that should be on at all times.

[knoxrebel]

Re: Dell 2408wfpb

Power going to inverter board
1 BL 23
2 BR 23
3 R 23
4 O 23
5 Y 23
6-10 Ground

Going to Video Board

Bl 0
NC 0
BR 23
R 0
O 23
Y 23
G 0
Blue 0
Black 0
Gray 0

[selldoor]

Re: Dell 2408wfpb

Were they exactly 23.00 or 23.99 or 23.01
I think were aiming for 24v so the rest of the decimals is important
Now to find the 5v

Have you got the board part numbers as requested

And what does the black writing say on the board edge