Medion MD41527 PS b/d hissing/crackling noise

[notallbad]

PS b/d: Delta DPS-210EP B Rev:00

The moment the rocker switch is turned on (tv comes on in standby) there is a hissing/crackling noise (possibly arcing) coming from the PS b/d, I have managed to locate the culprit which appears to be the large blue cap just under the transformer, after a few seconds the noise stops until the tv is turned on, out of standby, the noise then persists all the time the tv is on.

Is it just likely that the cap needs replacing, what one do I get and where, thanks.

Cap - MM225K 450V

[tom66]

Re: Medion MD41527 PS b/d hissing/crackling noise

There are other possible causes of this. Check the voltage across the large 400V cap. If it's low, then you may have a PFC problem causing the hissing/crackling noise.

[notallbad]

Re: Medion MD41527 PS b/d hissing/crackling noise

Just to be sure you are referring to the cap with the markings 4326AW?

[tom66]

Re: Medion MD41527 PS b/d hissing/crackling noise

Yes.

[notallbad]

Re: Medion MD41527 PS b/d hissing/crackling noise

OK, back soon, need to put board back in and check.

[notallbad]

Re: Medion MD41527 PS b/d hissing/crackling noise

380v when first powered on then settles down to 320v, this is in standby.
Switch on from standby, goes back up to 380v and remains constant whilst the tv is on. Occasionally dips to 379v.

[tom66]

Re: Medion MD41527 PS b/d hissing/crackling noise

OK, that's fine. Are you sure the noise isn't coming from L1, the coil next to the capacitors?

[notallbad]

Re: Medion MD41527 PS b/d hissing/crackling noise

Well, I touched the 2 blue large caps and the coil but the vibration mostly seems to be coming from the top blue cap and when moving each of these components its the top blue cap moving that makes the noise change.

I could try resoldering the joints but they look good from the solder side of the board.

[tom66]

Re: Medion MD41527 PS b/d hissing/crackling noise

I would try dabbing glue on L1, if that doesn't work then it may be the capacitor. Note that in some cases those capacitors can be microphonic (produce noise from current flow), part of their operation, not something which can be avoided easily.

[notallbad]

Re: Medion MD41527 PS b/d hissing/crackling noise

The noise is quite audible and the volume on the tv would need to be turned up loud to drown out the cap noise, so not normal operational noise which I have heard before on some tv's and knew theres not much that can be done about it and in any case not very audible so can be ignored especially when the casing is put back on.

[notallbad]

Re: Medion MD41527 PS b/d hissing/crackling noise

OK, i have glued the coil but not much change, maybe slightly reduced but thats probably due to the glue being packed between the coil and cap.
I think I shall try re-soldering the joints to see the results then apply glue between the cap and transformer side.

[notallbad]

Re: Medion MD41527 PS b/d hissing/crackling noise

Re-soldered - no change.
Really do think its the cap at fault.

What can it be replaced with? And where to get one?

[notallbad]

Re: Medion MD41527 PS b/d hissing/crackling noise

Datasheet for MM225K 400V Cap available here:

http://translate.google.co.uk/transl...38%26bih%3D520

Metallized polyethylene terephthalate film capacitor

Will just any 2.2uF 400V +/- 10% tolerance poly/mylar cap do?

[tom66]

Re: Medion MD41527 PS b/d hissing/crackling noise

Must be polyethylene, cannot use class X or Y.

[notallbad]

Re: Medion MD41527 PS b/d hissing/crackling noise

So searching for polyester, polar polymer, PET but no joy!

Looks like I'm going to have difficulty finding one.
Craplins which is local to me don't do them, noone is listing any on fleabay,
a(rs)e -online and fartwell if they do have them its then the postage costs on top, which is not too bad for arse-online if it solves the problem.

Is this suitable?
DME4W2P2K-F
http://uk.farnell.com/cornell-dubili...00v/dp/1174652

or this?
ECQE4225JF
http://uk.rs-online.com/web/p/polyes...itors/6224892/

The physical size of these looks bigger too, which may be an issue.

[tom66]

Re: Medion MD41527 PS b/d hissing/crackling noise

First one will cost you £20!!

Try this
http://uk.farnell.com/panasonic/ecqe...2uf/dp/1744825

[notallbad]

Re: Medion MD41527 PS b/d hissing/crackling noise

Thanks Tom

But the dimensions seem excessive, mine is approx. 16mm long, 20mm high and 13mm thick.

If the ones I order are truly 31mm long, 29mm high and 31mm thick I will have difficulty fitting it on the board in its original location.

[notallbad]

Re: Medion MD41527 PS b/d hissing/crackling noise

There is a heatsink plate that fits over the top of the boards, not shown in the photo, so the height is an issue too.

[tom66]

Re: Medion MD41527 PS b/d hissing/crackling noise

Not sure then how to solve the issue, as it looks to be a hard to find part.

[ben7]

Re: Medion MD41527 PS b/d hissing/crackling noise

Two smaller capacitors in parallel?