Refrigerator power board making horrible high pitch noise - Page 1
Forum section: electronics / repair

author: coolboarder
author_rank: Newbie
timestamp: August 31, 2015, 01:15:38 am
content: Please help me my refrigerator is driving me insane. It is like there is an evil high pitch noise maker in it. The guy I bought it from on craigslist didn't have an explanation of why he was getting rid of it but now I know why. It is making a high pitch noise like a dog whistle that can be heard from the other side of the house. After searching and hoping it was not the compressor I finally narrowed it down to the power PBC. It seems like the part I have the arrow pointing to is what is generating the noise. If I push on it hard while it is running I can get the tone to change. I could buy a new board for about $100 but I would rather try to repair this one if for nothing more than the satisfaction of doing it myself. What is the part called that the arrow is pointing to? Where could I find a replacement for it? I tried searching for the number on the top of it DA27-0020A but it did not yield any useful results.

author: briselec
author_rank: Regular Contributor
timestamp: August 31, 2015, 03:11:31 am
content: https://www.midwestapplianceparts.com/index.php?main_page=product_info&cPath=3511_3514_3529&products_id=375983&zenid=i5j2k6c5pg4n77a584g3t6c8v7

author: nowlan
author_rank: Frequent Contributor
timestamp: August 31, 2015, 03:52:45 am
content: Is coil whine caused by voltage ripple. Can glue inductor to stop it vibrating, but ripple remains?

author: coolboarder
author_rank: Newbie
timestamp: August 31, 2015, 04:16:44 am
content: Thanks for the link.I'm reading up on coil whine and ripple voltage now. Seems like a common problem with PC video cards since that is what most link I find relate to. Will replacing the coil likely fix the problem? Or is there likely a larger problem with the board?Glue seems like the quick and cheap fix to try. Should I use hot glue?

author: mij59
author_rank: Frequent Contributor
timestamp: August 31, 2015, 04:46:46 am
content: To dampen the inductor you need something like transformer varnish, transparent or amber Tectyl may also help, but is kind a smelly.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: August 31, 2015, 08:47:55 am
content: What is IC3?What is the base frequency of the whine?What is the base frequency of the of the output ripple on the scope, and does the waveform seem ok? (If you can measure safely.)Does the whine change with load?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 31, 2015, 03:46:43 pm
content: Without going into great detail about the circuit, its operation, and the function and operating range of the component in question, about the best we can suggest is:- Secure it to make sure it isn't vibrating loosely. Varnish is good for this. It probably is varnished already, so don't get your hopes up.- Dampen it to reduce the amount of vibration. Add some stiff rubber or foam goo (e.g., hot glue, "hot snot", some urethane glues?) and see if that helps.- You may have no choice but to acoustically shield it instead. Add foam pads, rubber dampers to the PCB screw holes, close openings in the 'fridge enclosure, etc.Mind that, if it gets warm in operation, you don't want to crowd it too much with gooey stuff. You may have to live with it...Tim

author: coolboarder
author_rank: Newbie
timestamp: September 01, 2015, 02:07:48 am
content: Hot glue was the only thing I had on hand so I tried slathering it in hot glue doing my best to get the glue down in the coil windings. It cut down on the noise a little bit but still loud enough to annoy me in the other room. The sound is just too maddening so I ordered a new board on ebay with overnight shipping. Even if I muffled the sound hearing that high pitch whine faintly would still drive me insane.Here is a video of the sound:

author: Vincent
author_rank: Regular Contributor
timestamp: September 01, 2015, 02:18:15 am
content: Ideally you'd need transformer varnish for this, as it's been said. Desoldering the transformer and dipping it in the varnish for a while (not the pins though LOL) would likely fix it.Lots of mains transformers and ballasts could be saved from scrap just with a little bit of varnish!

author: jitter
author_rank: Frequent Contributor
timestamp: September 03, 2015, 06:55:19 pm
content: Quote from: coolboarder on September 01, 2015, 02:07:48 amWow, that's maddening indeed. I can understand why you went for a new board. But I do hope it doesn't suffer from the same problem.Googling the part no stuck on the blue cap ("GGH inverter 190C") I found a Samsungservice manualfor a fridge that uses the same board. Page 116 has the schematic and your noisy part is a coil. I can't see the refdes in the photo, but it guess it's L101. It's a 1 mH 400 mA coil.IC3 is a non isolated DC/DC converter (BP5047BP15) by Rohm. Rohm recommends that a coil is used that doesn't easily saturate at high temps. I wonder if that would have anything to do with the noise... They recommend the MitsumiC10-FR1.0mH, which is not what Samsung used. So if your new board gives you the same aggro...(hope not) it might be worth trying to source this coil (according to the datasheet "for preventing the diffusion of noises generated from power circuits").That this thing is prone to making noise is actually expected judiging by the fact that the cap and resistor on pin 10 of IC 3 are for noise reduction. Both parts should be optimised based on actual noise performance, but Samsung seems to have chosen the lowest recommended values for both.Let us know if the new board isor still...

author: aargee
author_rank: Frequent Contributor
timestamp: September 04, 2015, 02:20:10 am
content: Ideal solution is the varnish but using a vacuum jar. This will effectively remove all the air from the windings and replace it with varnish.Remove the transformer, get a small jar with varnish and submerge it. Put the smaller jar in a vacuum chamber. The chamber we used to use was just a large sealed glass jar connected to a venturi vacuum that was run connected to a flowing water tap and let it run for 1/2 to 1 hour.Though this may exceed the effort you want to go to.

author: coolboarder
author_rank: Newbie
timestamp: September 04, 2015, 05:05:27 am
content: I put the new board in today and at first it was making the same noise but after it warmed up it seems to have quieted down. Hopefully the noise is gone for good. If the new board makes any noise I'm going to varnish the old board and swap them out. I have a vacuum pump for doing car A/C systems so I could do a vacuum chamber. I would just have to order the varnish. At least I wouldn't have to worry about food spoiling while I work on the board.Thanks for everyone's help!

author: jitter
author_rank: Frequent Contributor
timestamp: September 04, 2015, 05:39:15 am
content: Good to know your problem is solved, for now.I'm inclined to believe that Samsung's choice of components around IC3 were more cost-driven than performance driven, especially since the temperature has a big effect on the noise. Should ageing have an effect on those component's values, my guess is that the noise might gradually return. If that's the case, I recommend experimenting with the values of those components and the type of the inductor, as the manufacturer or IC3 recommends (datasheet linked in previous post).I wouldn't recommend putting anything over the coil if it gets hot.

author: Bryan
author_rank: Frequent Contributor
timestamp: September 05, 2015, 10:50:45 am
content: If I had the board out I think I would change out the electrolytic caps with some good quality replacements. Likely cheapies and the ESR will shoot up over time. Who knows maybe that is the problem all along. A lot of ripple on the output voltages.