Medion MD41527 PS b/d hissing/crackling noise

[notallbad]

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

Replaced the 2.2uF 400V cap and its still making the noise.

Any ideas anyone please or do I just need to keep changing component?

Thanks again

[tom66]

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

I still think it's that inductor/coil near the cap.

[notallbad]

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

What can be done about that? What can it be replaced with?

[tom66]

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

Not much... Could be a minor crack in the core, leading to high frequency oscillation, or worn enamel on the wires. You can try using glue, but it may not work.

[notallbad]

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

Yes, already tried glue and didn't help.

So a replacement then?

What am I looking for? Inductor/Coil How many uH's?

[notallbad]

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

Yes the insulator looks a little worn.

[notallbad]

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

So according to schematic its one of these

CR-18-LP3009/86.4UH

[tom66]

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

I reckon if you could get this to fit it would work fine.
http://uk.farnell.com/panasonic/elc1...064/dp/1749178

[notallbad]

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

Before changing that cap the noise would change according to touching and moving the cap but now it has been replaced there is no change when touching/moving it.

The sound is now with the cap on the other side of the coil.

[notallbad]

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

So what could it be if I replace the coil and its still doing it?
Thanks

[ben7]

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

I reckon if you could get this to fit it would work fine.
http://uk.farnell.com/panasonic/elc1...064/dp/1749178

Tom66: I was thinking about this, could a bad capacitor on the secondary side be causing instability in the smps, resulting in this? Like, high peak currents could be causing the capacitors' foil plates to vibrate? I know this is part of the PFC circuit.

Notallbad: have you tested the other blue capacitor?

[notallbad]

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

Hi
Thanks for response.
No not tested it, only have a cap meter, not esr or lcr meter.

The one I (replaced) removed was spot on 2.2uF with the capacitance meter.

I understand your comments and I was wondering that myself and thought about checking/replacing the secondary caps just to see.

Though I was wondering if the bridge rectifier could have something to do with it?

[notallbad]

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

The other cap, MM105K, measures just under 1uF.

[ben7]

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

You can take a plastic straw, put it up to your ear, and poke (listen) around to see if it is the capacitor making the noise.

[notallbad]

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

Funny you should say that, just this afternoon I was doing exactly that and although I could hear noises from most components there was a cap that sounded like it was making a noise rather than being transmitted through the ccts or via vibration. Yet to check it out!

As a note : It is on the secondary side.

I think I shall be removing and check all the caps anyway even though they do look OK.

[notallbad]

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

Replaced all electrolytic caps on secondary side and the coil as suggested to no avail so looks like I'm gonna have to give up on this one, shame.

Also the on/off rocker switch was crackling/arcing too when switching it on and off so have replaced that too!

[ben7]

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

Actually, could you test that grey capacitor that is in between L1 and the main transformer?

[notallbad]

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

Reads 0.02 uF and has .022 printed on it!

[notallbad]

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

From reading topfli8979's thread 'Magnavox LCD 37mf437/37 chirping' and seeing a cap and diode repair kit that apparently repairs the fault it got me to look at the board again in hope I would discover something.
Of course I don't know what 'chirping' is exactly so it may be what this board is producing.

I would have thought if a diode was shorted or oc it would give different results but anyway decided to remove to 'test'.

SB360 Schottky barrier rectifier - DMM diode test reads 246 and 20k ohm test reads 257, OL with probes reversed

P6KE200A 600 Watt transient voltage suppressor - DMM diode test reads 755 and 20k ohm test reads 12.76k, OL with probes reversed

Not sure these tests are conclusive believe I need a variable PS for the suppressor.

[tom66]

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

Chirping is bursts of pulses, different fault to yours.