Dell P2214H monitor is dead, not turning on.. Caps look good

[Goforth]

Hi guys! Title says it all. My Dell monitor will not turn on. No LED lights, no nothin. All of the caps look good, no bulging at all. No cracks in the solder joints, although one joint looks a little rough. Any ideas? I don't know much about this stuff (obviously), however, I am fairly good at soldering. Figured I'll give it a shot fixing it. After all, it's not like I can break it I am limited to a multimeter when it comes to testing. Also, I can get better pictures upon request. Thanks, fellas!

Monitor is a Dell P2214H
Photos:
https://ibb.co/eBVqh5
https://ibb.co/n4Z5FQ

[Goforth]

What should the DC voltage be on this cap?

This board came out of a monitor that won't turn on. The large cap in the picture says 450v, but when I check it with a multimeter while the board is plugged in I'm getting 160ish volts DC. Could this be the issue?

I'm no guru with this stuff, I just figured if the cap says 450v, then it's strange I'm reading 160v. But maybe I'm wrong. Teach me something
https://ibb.co/hwnzc5

[mariushm]

Re: What should the DC voltage be on this cap?

Modern switching power supply use Active Power Factor Correction circuits which boost 90v..250v AC to 400..420v DC for better operation.

In this case either the APFC circuit isn't working or it doesn't exist. You have 110v AC coming in, going in the bridge rectifier resulting in DC voltage with a peak of sqrt(2) x 110v = ~ 155v

If your PSU has no pfc, then probably they kept the capacitor with such high rating in case the monitor was going to be sold in countries with 230v AC at the socket (those would have ~ 330v DC max... so any cap rated for more than 330v+~10% would do... and 420 or 450v rated capacitors are common and suitable for this.

[eccerr0r]

Re: What should the DC voltage be on this cap?

Depends on the PSU. This one looks like it's a non-PFC autodetect PSU, maybe a 384x design. The input needs to be able to deal with 120V and 220VAC mains, so the capacitor voltage needs to be able to handle both. While 120VAC is 160-170V, the 220V input would produce 320-340V which the 450V cap will handle.

[redwire]

Re: What should the DC voltage be on this cap?

OP please post the make/model of what you working on, or start a thread on it.
It appears to be 4H.0EH02.A04

170VDC is what I would expect on the cap, there is no active-PFC.

[Per Hansson]

Re: What should the DC voltage be on this cap?

OP please post the make/model of what you working on, or start a thread on it.
It appears to be 4H.0EH02.A04

And PLEASE stop hotlinking an image host that does not allow it!
Here is a FAQ on how to upload the images here:
https://www.badcaps.net/forum/showthread.php?t=1868

[PeteS in CA]

Re: What should the DC voltage be on this cap?

Depends on the PSU. This one looks like it's a non-PFC autodetect PSU, maybe a 384x design. The input needs to be able to deal with 120V and 220VAC mains, so the capacitor voltage needs to be able to handle both. While 120VAC is 160-170V, the 220V input would produce 320-340V which the 450V cap will handle.

This power supply doesn't have PFC - no PFC inductor, only one transistor/MOSFET on the primary side. Going a step farther, it looks like a flyback design, since there is no output inductor. Finally, unless there's a SMT PWM IC on the underside of the PCB, I'd guess this is a self-oscillating flyback design.

Since the OP is from the US, the ~160V across the input cap is correct, and means the input fuse is OK. That means the switch transistor/MOSFET is not shorted. If there's no output (especially if there is a clicking sound when it's powered on?), I'd look for shorts on the output side.

[Goforth]

Re: What should the DC voltage be on this cap?

OP please post the make/model of what you working on, or start a thread on it.

The monitor is a Dell P2214H. Having trouble finding the issue. I was hoping a cap would visually be bad, but it's never that simple (not for me at least).

[Goforth]

Re: What should the DC voltage be on this cap?

My apologies Hansson, won't happen again. Thanks for the instructions.

[Agent24]

Re: What should the DC voltage be on this cap?

If it does nothing at all, you may have an open-circuit startup resistor

[PeteS in CA]

Re: What should the DC voltage be on this cap?

A picture of the underside of the power supply, if there are SMT components there might be helpful.

[stj]

Re: What should the DC voltage be on this cap?

change c606

[budm]

Re: What should the DC voltage be on this cap?

So are you getting any DC outputs on the connector at all (you did not indicate what DCV you are getting on those two output connectors)? It is just simple always on power supply (no PFC) with two outputs (one rectifier on the heatsink, and one axial-lead rectifier).
https://cdn.badcaps-static.com/pdfs/...ea2905eb95.pdf

It will work with incoming Voltage range from 100VAC ~ 240VAC, thus the 450VDC cap is being used.
Page 12:
AC input voltage/frequency/current: 100 VAC to 240 VAC / 50 Hz or 60 Hz + 3 Hz / 1.2 A (typical).

You should stick to this thread: https://www.badcaps.net/forum/showthread.php?t=63524

[PeteS in CA]

Re: What should the DC voltage be on this cap?

change c606

Whether self-oscillating or in the start-up circuit for a 384x PWM IC that would be a suspect.

[Per Hansson]

Re: What should the DC voltage be on this cap?

You should stick to this thread: https://www.badcaps.net/forum/showthread.php?t=63524

I have merged the two threads.

[Goforth]

Re: What should the DC voltage be on this cap?

So are you getting any DC outputs on the connector at all (you did not indicate what DCV you are getting on those two output connectors)?

I tried checking the DCV on the two white output connectors in the right side of the picture, I can't seem to get any readings.

[Goforth]

Re: What should the DC voltage be on this cap?

A picture of the underside of the power supply, if there are SMT components there might be helpful.

Here you go

[budm]

Re: Dell P2214H monitor is dead, not turning on.. Caps look good

So 0VDC on the connectors.
Try heating up C606 (or just replace it as suggested by STJ) with hair dryer for a minute and then power up the board to see if you will get any DCV on those two connectors.