Fridge control board repair and capacitor identification help

[nbd]

Hello

I know this might be a bit of a long shot, but I saw that users in this forum helped with identifying other miscellaneous electronics, so I figured I'd give it a shot.

I have a fridge that just died, it lived a fairly long life and just ran out of life last night, no life what-so-ever. Mains power going into to the control board using a voltage detector, and that's about as far as it got.

I examined the board and found the VIper12A IC seems to have damaged itself, with a blowout next to one of the source pins, there is also a ceramic disc capacitor that connects the source pins and the FB pin of the Viper; it was leaning over against the Viper IC and seems to be sorched pretty badly (completely obscuring any text on it). I'm not entirely sure if the capacitor is damaged internally, or just scorched I only see surface marks on it, no cavities; so it might just be the VIper?

So my 2 questions are:
Can anyone help identify the capacitor? C41 on the PCB.
and, is just replacing the viper viable? (or is the failure in the viper caused from something else/ the capacitor almost surely damaged too)

I've included some photos below that should hopefully show a lot more than I am capable of explaining. I tried searching around but didn't have much luck finding anything online. This is the PCB in question (P/N B810195-410Q) : https://m.bigwarehouse.com.au/haier-refrigerator-htmr575wh-power-contoller-p-1788138.html?cPath=81300_99335_101935

Again I know it's a long shot, but I hope someone here might magically know something that can help.

_{side note: first time posting - haven't used a forum since I was small person, so apologies if I make a mistake or post in the sub forum}

[CaptDon]

What are the chances of finding a new control board? If you repair the old board you must get all of the carbonized crud off of the board since it is highly conductive and may arc or burn. If there was no local power surge or lightening in the area when the unit died then it is possible the SMPS transformer with the red tape body developed a shorted turn and caused the I.C. to burn out. Replacing the I.C. wouldn't help in that case.

[wraper]

That capacitor most likely is OK, just needs some cleaning. Also you need to replace 2 nearby electrolytic capacitors. Even if they're working so far, they received a lot of beating due to high heat that darkened the board.

[wraper]

What are the chances of finding a new control board? If you repair the old board you must get all of the carbonized crud off of the board since it is highly conductive and may arc or burn.

Does not look carbonized, just darkened PCB due to prolonged heating. Just replacing bad components and cleaning PCB from magic smoke should be fine.
Common mode choke (T2) looks fried too but it can be easily replaced with off the shelf part or even 2 jumpers (for testing or if you don't care about EMC).

[timeandfrequency]

Hello nbd,

It looks not that bad. Maybe you can give it a try.
The good quality pictures you provided are of great help to give you a piece of advice.

Clean the board with isopropyl alcohol (denaturated alcohol is OK too) by using an old bent toothbrush.
Dry the board in sunny weather (or in your kitchen klin : 50°C   30 minutes)
As other members stated above, change all of the electrolytic capacitors (C36, C37, and C39) and verify the 4 diodes (D9, D10, D12, D13). Check the F1 fuse.
Viper of course must be replaced too. You might use a DIL-8 quality socket.

Once the parts replaced, proceed as follows :
- Disconnect the hermetic compressor.
- Then, on the mains side, connect an incandescent bulb 25 W, 40 W should do too  (120 VAC or 240 VAC depending your mains) in SERIES with the board  (towards the white mains connector).
- If the bulb lights firmly, there's still a short.
- If the bulb just flashes and then glows weakly, your board is probably repaired. Viper's low output voltage should be checked with a multimeter.

[nbd]

Common mode choke (T2)

Is that what T2 is. I'm not super well versed with electronics, just know a few basics. I did look on it for any print to say what it was, the copper windings on it (there are 2 side by side) seem to be in good condition, just a bit of a weird flaky build up on top of it. It would be nice if I knew what part it was, if I were to opt to replace it, I can't figure out any way to ID it. I'm in australia - so 220-240 V and 50 Hz AC is mains power, according to google. Everyone just calls it 240 here, even though it's not entirely accurate.

What are the chances of finding a new control board?

That was my first port of call, even if only to see the original print on that capacitor. Given the fridge has been off the market for a long long time, I haven't found anything beyond parts like that site I linked, which was more than half the value of the entire fridge. If it can't be fixed, then it can't be fixed. I just figured, all the mechanical components are in good order, this board looks to be in great condition besides this one burn area; I figured if I could repair it for the cost of a few chips and resistors why not give it a go.

Clean the board with isopropyl alcohol (denaturated alcohol is OK too) by using an old bent toothbrush.
Dry the board in sunny weather (or in your kitchen klin : 50°C   30 minutes)
As other members stated above, change all of the electrolytic capacitors (C36, C37, and C39) and verify the 4 diodes (D9, D10, D12, D13). Check the F1 fuse.
Viper of course must be replaced too. You might use a DIL-8 quality socket.

That's good to know, I use 100% iso to clean basically everything else; being australia outside is getting close to 50°C anyway for drying . It's good to know about the other capacitors, I found the Viper on Mouser Electronics, and shipping is the same regardless of what I order, so I wanted to know everything I needed upfront before getting the viper. The fuse I checked before even spotting the burn, still looks new, I assume verifying the diodes is just a diode/continuity test on the multimeter.

[u666sa]

Cap is fine. Its value is 47 1KV just like the other one. You have the chip go puff on you. You see it?



What is the chip? KDR004?

Whether you repair this thing or not depends on whether you can find same chip or similar to it chip. This can help, but I don't know --

[u666sa]

https://www.avrobot.ru/media/products/0208384001457553279.pdf

There is even schematics. So you can remove the chip and check what caused this thing to blow up.

[timeandfrequency]

Hello nbd,

You have the chip go puff on you.

I noticed it too on nbd's picture.
This one was a lateral magic smoke 


Yes T2 is a common mode choke/filter. Some litterature about that topic.

[...] I assume verifying the diodes is just a diode/continuity test on the multimeter.

It is wise to first desolder the capacitors. Then set your multimeter in Diode test mode. For each diode, you should read about 0.6 VDC ± 0.1 VDC in one way, and nothing/overflow in the other way.
You may also check the other diodes on the board.
You may even have a look to the IR diode embeeded inside the optocoupler U11 (maybe a PC817 or similar?).  The IR diode forward voltage should be 1.3 VDC ± 0.2 VDC.

If you own a small lab power supply featuring a current limitation, we might even be able to have a glimpse of the health of the secondary (low voltage) side. If you want to go that way, I'll be more specific in a coming post.

[nbd]

Hi all.

Thanks for the help so far. I got it repaired (kinda). I replaced the Viper and a couple of components, found there was no power reaching it.

Essentially the circuit path is mains, 25A fuse (presumably for the mechanical stuff), then feeding all the AC side of the relays, as well as a 5W 10ohm wire wound resistor that feeds to live side of the full bridge rectifier, then the a capacitor between the positive and negative rails, then through the choke positive on say channel 1, negative on channel 2, then another capacitor again across the 2 on the other side of the choke, then each rail off to the viper and SMPS respectively etc.

Ended up discovering the wire wound resistor was open, I replaced it in my second round of attempting to fix and everything was working good now (almost). As someone mentioned, the choke was stuffed, or maybe I stuffed it when I cleaned it, I'm not sure which. One channel is fine, the other is busted with a couple of breaks. I took it off the board and just put in 2 jumps in the interim which is how I was able to verify everything was operational again, however long term it probably isn't health to just leave jumps there? and I should replace the choke with a new one.

My biggest issue is I'm doing my head in trying to find out anything useful about the existing choke so I can source a suitable replacement. I'm pretty uneducated with all this so I'm not sure how people even figure out what specs are suitable for a choke. All I really know is the physical properties of the choke. I'm hoping that someone can help.

So we know the voltage coming in from mains is 240-250VAC @ 50Hz (typical Australian mains power); then is gets rectified before the choke to DC which I understand ends up being like 350-400VDC or something? from what I read. (I don't much understand it sadly).

The choke is dual channel UU type core.
The copper wire used on the winding is thin, really thin. My digital Vernier calipers said the wire is 0.1mm thick; though my calipers are pretty old and a bit unreliable, so I'm not sure how precise that is.
I unwound the broken winding; given couple of breaks I don't have a perfect turn number, but I counted 214 turns with a couple of turns either side to account for the loose unspooled breaks.
I measured about a length of 4.6m of copper wire.
The U shaped core is inserted into a plastic shroud that the winding is wound over, that shroud measures a side length of 5mm, it is a rectangular box shape, the winding is multilayered over it, which builds it up to an overall diameter of about ~8mm and the length/space it is wound out over is 3mm. all of this is obviously mirrored on the other channel with the other "U". as for the core itself, from the part of the U-core that is open

The length of the whole choke is 16mm length 10mm width. 16mm is the length of the 2 U cores end to end. Pins are 7mm apart on each channel and 8mm apart between the 2 channels.

I'm assuming since it's feeding through that rectified VDC of something like 350 or 400, given how thin the wire is it current draw must be pretty low to the viper and the SMPS? I needed both channels working to measure the inductance though. So I'm at a total loss for knowing what is suitable in terms of inductance/impedance for replacing this choke. I can find plenty that look right; basically UU chokes all look the same, but with no marking on this one I'm really struggling to find a replacement. Maybe it would be possible to determine what it should be based on the known incoming voltage, it's wire thickness as a max current, and knowing it feeds a viper and a SMPS?

Long post I know.. just wanted to put as much info as I could think of upfront if anyone can anything that can help

[timeandfrequency]

hello nbd,

If you want to replace T2 (common mode choke shown in figure 8 above), you do not need an exact replacement.
The replacement part must have at least the same wire diameter and the same pin positionning. Other features are not that relevant in your case.

Have a look at Mouser to see if you can find a suitable part :
https://eu.mouser.com/c/passive-components/inductors-chokes-coils/common-mode-chokes-filters/?product=Common%20Mode%20Chokes&srsltid=AfmBOor0ae0RmMRbLr-eB70nsRdo1dWoUgXOAp9QPKDlw_US4aJ7RLL1

[nbd]

The details of their function is a little over my head. My main concern is I don't really comprehend the impact of inductance and impedance etc in the choke, and suitable components seem to widely vary in their values of these metrics. (I dont know the impact of putting in one that is far higher / lower than the preexisting one).

that's why I guess I'm asking for anything, even with just knowing the application and voltage; if there is an expert that could say a relatively "safe" range I should be aiming for since I've seen that style ( same size, UU core, pin positioning etc) but in a variety of different wire thicknesses (wire gauge isn't listed on anything so it's hard to tell) but inductance values from 0.4mH up to like 30mH and impedance can vary even more extreme between products. I feel like just picking one at random would not be a great idea.

[timeandfrequency]

Selecting the 'best' common mode choke and then confirming the choice made by validating its ability to successfully filter out most of the noise generated by the switcher goes far beyond what can be done in 99 % of all electronic labs (hobby or professionnal).
These kind of measurements need to be perfomed in EMI labs where conducted interference level are carefully mesured, by skilled people using dedicated test equipement.
This process is only required if you want to sell a new product.
Don't worry about your fridge : replace the defective choke by using two straight wires, and this will be good enough for Australia (as Dave from the EEVblog often says).