Chest FREEZER Whirlpool AFG 605 DGT - Identification of faulty PCB transformer

[JohnMcC]

Hello,

Please can anyone help me identify this PCB transformer, shown in the attached photo. (The large blue transformer)

The Chest FREEZER Whirlpool AFG 605 DGT was bought in France.

It states on the blue transformer that the secondary output is 66V 2VA............but this seems very strange to me ?????
Very high voltage for a PCB board ?
Is it possibly 6.6v ???

The Borocco L7805 CV Voltage Regulator (which is downstream of the blue transformer) states that the voltage IN is between 7.5 and 35v
so the secondary output on the blue transformer does not make sense !!!

Any help would be much appreciated, especially on where to get a replacement transformer.
(From the markings on the transformer I can see it was made in Italy, but cannot make out the name of the Company)

Thank you

John

 

[ronsimpson]

6V 333mA 2 watt.
That will put 8 to 9 volts on the capacitors.

 

[spec]

SAFETY WARNING This thread involves dangerous voltages. Please observe appropriate precautions and if you are not experienced in high voltage electronics please do not carry out any work yourself.

Hello,

Please can anyone help me identify this PCB transformer, shown in the attached photo. (The large blue transformer)

The Chest FREEZER Whirlpool AFG 605 DGT was bought in France.

It states on the blue transformer that the secondary output is 66V 2VA............but this seems very strange to me ?????
Very high voltage for a PCB board ?
Is it possibly 6.6v ???

The Borocco L7805 CV Voltage Regulator (which is downstream of the blue transformer) states that the voltage IN is between 7.5 and 35v
so the secondary output on the blue transformer does not make sense !!!

Any help would be much appreciated, especially on where to get a replacement transformer.
(From the markings on the transformer I can see it was made in Italy, but cannot make out the name of the Company)

Thank you

John

Bonjour John,

Welcome to ETO. Which part of France are you from? If you put it next to 'Location' on your user page it will show in the box at the left of your posts.

If I read you correctly, you suspect that the blue transformer is faulty. Why do you think that?

I haven't investigated a replacement transformer or analysed your circuit in detail, but I suspect that the circuit simply comprises a mains transformer, rectifier, reservoir capacitor, and three-terminal voltage regulator (L7805) to provide a 5V supply line, just as you imply. The only complication that I can envisage is that the transformer secondary may feed another circuit, like a zero voltage detector, for example.

Those small low-power (2W) mains transformers have very fine primary windings which are prone to go open circuit. The bad news is that it may be impossible to get an exact replacement transformer, but the good news in that, with a bit of ingenuity, you should be able to fit another model of transformer that will do the job well or even better. But I would advise getting a sealed transformer, like the original.

A replacement transformer would need to meet the following requirements;
(1) Primary: suitable for the mains in France (230V AC RMS at 50Hz)
(2) Secondary voltage: 6.6V. If you cannot get this exact voltage, a slightly higher voltage will be fine.
(3) Power rating: 2W. Any power rating of 2W or greater will be suitable (but the transformer physical size will be the limit)

There are many transformers on the market that will probably suit. I will investigate but if I can't find a suitable replacement transformer there are many ETO members who surely can.

spec

 

[spec]

Hi again John,

I have had a quick look on the net and can't find a suitable transformer.

But another approach you can use, providing there is no take off from the transformer secondary for another circuit, is to replace the faulty transformer by an off line 9V switch-mode power supply. This is just a thought at the moment.

spec

 

[JohnMcC]

Thank you "RonSimpson" and "Spec" for your replies.

I live just outside Paris, and have updated my "personal details" as you suggested to show where I live.
My home has 3 phase electricity (as do many in France), and unfortunately during the floods in June 2016, the underground electricity cables shorted out.
Temporary overhead cables were installed (and are still there !! now in November), but my cables were torn out by a dustbin lorry driver who did not see them !
The neutral cable was ruptured, and all my appliances in the house received 380 - 400 volts instead of 220 volts.
The insurance claim has been a total nightmare, and in France you are expected to show the original purchase invoices of your appliances if you make a claim. Not only that, the insurance writes the value down by 1.72% per month.
So after 5 years your appliances are considered to have no value !!!
Unfortunately the money I am likely to receive from the insurance will fall very far short of what it will cost to repair and replace.

I have a long list of things that don't work, including the Whirlpool freezer, a Daewoo microwave, a Samsung TV, a Pioneer HIFI, a tower computer, and a whole load of other smaller appliances like Radio alarm clock, home phone, wifi repeater, etc...etc..
In fact all the equipment that has electronic circuit boards in them.
Interestingly, all the PCB mounted transformers have blown in all of them on the primary coils. The secondary coils are ok, so I am hoping that everything downstream of the transformers will be OK.

The problem is I cannot find the PCB mounted transformers anywhere.

I thought I would post my first message (about Whirlpool freezer) on this forum to see if I received any replies. I have done, for which I thank you.

The transformer for the Whirlpool freezer is one of the simplest, because it only has one output voltage.
Do you think I can replace the burnt out 6.6v transformer with a 6v one, or would it be better to buy a 9v one ??????

The Daewoo microwave and Pioneer HIFI both have transformers with multiple output voltages (3 different voltages), but I will make another posting on this forum to describe them, hoping that you may have the time to help me.

Many thanks again, and kind regards,

John

 

[spec]

Hi John,

You are from Paris My wife loves Paris!

What a nightmare you have had. Luckily all the equipment you described may be fixable, but if the big transformer in the microwave has blown that would write the microwave off.

Can I ask what skills and equipment you have so that we can get an idea of what is feasible.

You ask about a 6V or 9V transformer. That is something I have been looking at too. If the circuit is in fact just a simple low power power supply, 9V may be suitable, provided the reservoir capacitor has a voltage rating of 13V or more. It would be possible to put a couple of cheap and small components in series with the transformer secondary to reduce the voltage by 2V or so.

7.5V is another standard transformer voltage which would be ideal, but less common.

The board looks very simple. Is there any chance you could trace out the circuit from the secondary of the transformer, including the reservoir capacitor, rectifier, and the three terminal regulator. Look for any other connections to the transformer secodary.

Incidentally, the L7805CV, 5V, three-terminal regulator is made by ST and was encapsulated in Morocco. https://www.mouser.com/ds/2/389/l78-974043.pdf

spec

 

[debe]

Same thing happened to me with a Westinghouse fridge, the board was going to cost $200 Australian. Going by the relay voltage on my board at 12V, went looking for a 13 to 15V transformer from scraped apliances. I found this blue transformer in a scraped microwave oven & used that. Unless you was using the microwave oven at the time then the main HV transformer will be ok. Its more likely that the small LV transformer on the control board in the microwave is burnt out.

 

[spec]

Hi John,

Here are some 7.5V transformers:

(1) **broken link removed**
(2) **broken link removed**
(3) **broken link removed**

 

[Les Jones]

Here is another possible transformer . It is 6.0 volts rather than 6.6 volts so it may require replacing the 7805 with an LDO regulator. I think it is unlikely the pin layout will match so you would probably have to drill some extra holes in the PCB and add wire links to the pins. I found this on Farnell's webside by searcing for "transformer PCB mounted." If you do the same you may find one that is a better match.

Les.

 

[JohnMcC]

Thank you everybody for all your very kind help.
I have been out all morning and have just returned home to find all these messages, which is tremendous.

I will attempt to answer all the comments in your messages.

1) Spec, I am glad you wife loves Paris. I considered Paris the most beautiful city in the world 30 years ago ! It is much more dangerous than it used to be, and I am not racist, but the ethnic numbers are extremely high.

2) The Daewoo microwave oven problem is on the low voltage side. (It is not the huge high voltage transformer which is faulty).

3) My skills are very limited. I am a qualified mechanical engineer, but I studied all this 40 years ago, and can't remember the majority of it all ! However I can determine faulty parts on a circuit board with a meter, and know how to replace them if I can find the parts !

4) Whirlpool Freezer : The reservoir capacitor has a voltage rating of 25V

5) Whirlpool Freezer : The 7.5v secondary would be much better than the 9v, thank you

6) Whirlpool Freezer : The board is extremely simple. There is another board in the handle area of the freezer, which displays the temperature and allows you to control the freezer. I have taken this board out, and the components look fine and I hope there is nothing wrong with it.

7) Whirlpool Freezer : I can try and trace out the circuit, but there are some components that I do not recognise !

8) Whirlpool Freezer : I believe the L7805CV, 5V, three-terminal regulator is OK (not blown), but I am not quite sure how to test it with my meter. Obviously until I repair the Blue transformer, I cannot see if it outputs 5volts. I have removed it from the circuit board, and there is a resistance between all three terminals (Terminal 1 (input), Terminal 2 (ground), Terminal 3 (5v output)) . Resistance between terminal 1 and 2, 1 and 3, 2 and 3. Not quite sure how this regulator works, so what the ohm readings should be, have no idea.

9) Debe.............The price to replace this simple board is 133 euros plus postage. The other board on the freezer handle is 210 euros plus postage. So I wish to try and fix it myself !!! (Note: you are quite correct, on the microwave it is the LV transformer)

10) Les Jones, Thank you. You are correct the pin layout will not match what I already have, but I believe I will be able to manage modifications to the board and connect them with soldered wires.

I am overwhelmed by all your responses, and thank you.
I never expected so much help

Hope you all have a great weekend.

John

 

[spec]

3) My skills are very limited. I am a qualified mechanical engineer, but I studied all this 40 years ago, and can't remember the majority of it all ! However I can determine faulty parts on a circuit board with a meter, and know how to replace them if I can find the parts !

That is very reassuring. The majority of getting your units back in action will involve mechanical operations. And from what you have shown on the ETO images you can wield a soldering iron and squeeze a pair of pliers. Just remember the golden rule and never touch a unit that has more than 30V exposed.

4) Whirlpool Freezer : The reservoir capacitor has a voltage rating of 25V

Excellent

5) Whirlpool Freezer : The 7.5v secondary would be much better than the 9v, thank you

No problem John

6) Whirlpool Freezer : The board is extremely simple. There is another board in the handle area of the freezer, which displays the temperature and allows you to control the freezer. I have taken this board out, and the components look fine and I hope there is nothing wrong with it.

Sounds hopeful in view of reason for the failure. One strong posibility is that the overvoltage supressors on the mains input side will probably have blown. But we can cross that bridge when we come to it.

7) Whirlpool Freezer : I can try and trace out the circuit, but there are some components that I do not recognise !

Don't worry about that just draw a rectangle and note anything that is written on the component.We more or less know what the circuit should be.

8) Whirlpool Freezer : I believe the L7805CV, 5V, three-terminal regulator is OK (not blown), but I am not quite sure how to test it with my meter. Obviously until I repair the Blue transformer, I cannot see if it outputs 5volts. I have removed it from the circuit board, and there is a resistance between all three terminals (Terminal 1 (input), Terminal 2 (ground), Terminal 3 (5v output)) . Resistance between terminal 1 and 2, 1 and 3, 2 and 3. Not quite sure how this regulator works, so what the ohm readings should be, have no idea.

The regulator is a standard component and freely available for about $0.50US, so teat it with care if you want to avoid further heavy expendature. You can't make any meaningful measurements with a multimeter, except to check for dead short circuits.

Hope you all have a great weekend.

And you too John

spec

 

[JohnMcC]

Hi Spec,

I have photographed the circuit board, and the photos are attached.

The resistance R30 (5W100ΩJ) is on the input primary side of the transformer. It has blown. I replaced it hoping it would just be that, and the new one blew as well. (this was with everything left on the board).
The photos now show the board without the blue transformer, and the 5v voltage regulator which I have removed.

On the output of the blue transformer............it passes directly into the little round black component (AM106 8024)......no idea what this is.
From there it goes to the 5v voltage regulator with the capacitors on each side of the regulator.

The Orange component is just a relay.

Interestingly this freezer has remained running ...........the compressor runs all the time.
I believe the electronic part actually switches it off when it has reached the correct temperature (rather than the other way round, where it would switch it on)
That way if the electronics fail, as they have done, the compressor continues to run and you do not waste all the food in the freezer.

Does any of what I have written help you to make any assessment and recommendation please ?

On the primary 250v side of the transformer, when I switch the ohms to x100 or x10k.......it shows a reading, but it should show continuity on a x1 which it does not.
(The secondary coil shows continuity on x1 with no problem at all.)
My conclusion.........The blue transformer is faulty on the primary coil side.
My only question is why would the R30 (5W100ΩJ) blow again on the normal 250v AC

Many thanks,

John

 

[JohnMcC]

round black component (AM106 8024)......simple bridge rectifier.............found it on the internet !

 

[spec]

I have photographed the circuit board, and the photos are attached.

Great. Thanks

The resistance R30 (5W100ΩJ) is on the input primary side of the transformer. It has blown. I replaced it hoping it would just be that, and the new one blew as well. (this was with everything left on the board).

Hmm. That means that the 100R resistor must be connected directly across the mains supply.

On the output of the blue transformer............it passes directly into the little round black component (AM106 8024)......no idea what this is. From there it goes to the 5v voltage regulator with the capacitors on each side of the regulator.

Good. That black component is a bridge rectifier (as you said in the next post)

The Orange component is just a relay.

Right

Interestingly this freezer has remained running ...........the compressor runs all the time.
I believe the electronic part actually switches it off when it has reached the correct temperature (rather than the other way round, where it would switch it on)
That way if the electronics fail, as they have done, the compressor continues to run and you do not waste all the food in the freezer.

Sounds like a good approach

Does any of what I have written help you to make any assessment and recommendation please ?

Certainly does.

On the primary 250v side of the transformer, when I switch the ohms to x100 or x10k.......it shows a reading, but it should show continuity on a x1 which it does not. (The secondary coil shows continuity on x1 with no problem at all.)

The primary will be a relatively high resistance and the secondary will be a virtual short circuit. Can you measure the primary resistance and give me the reading from the multimeter? Can you also measure any secondary winding terminal to first one primary terminal and second the other primary terminal. The meter should show a complete open circuit on x10K.

My conclusion.........The blue transformer is faulty on the primary coil side.

I am not so sure.

My only question is why would the R30 (5W100ΩJ) blow again on the normal 250v AC

Could be an overvoltage protectors blown short, rather than the transformer.

I will digest what you have said and get back.

In the meantime, can you measure the resistance between the printed circuit pads that previously connected to the transformer primary?

spec

 

[JohnMcC]

Hi Spec,

Hmm. That means that the 100R resistor must be connected directly across the mains supply. YES, CORRECT

The primary will be a relatively high resistance and the secondary will be a virtual short circuit. Can you measure the primary resistance and give me the reading from the multimeter? Can you also measure any secondary winding terminal to first one primary terminal and second the other primary terminal. The meter should show a complete open circuit on x10K.

It is a high resistance. The primary on x10k goes right across the scale. On x100 it goes half way across the scale (Analogue meter and I cannot make out the figure on the scale. My digital meter is broken !)
There is no short across any of the primary and secondary terminals..........have tested all combinations.
If there should be a high resistance on the primary.............the transformer may be OK.

Could be an overvoltage protectors blown short, rather than the transformer.

Yes...........when I bought the new 5W100ΩJ ..........it was marked as a voltage regulator.............which I found odd for a "resistance" ??
Fortunately I bought 5 of them...............so I still have 4 spare.

In the meantime, can you measure the resistance between the printed circuit pads that previously connected to the transformer primary?

If I have read the scale correctly on the analogue meter........it is 300 ohms. The light blue resistor (R32) which is next to the 5W100ΩJ is across the terminals of the Primary.

Thank you
John

 

[Les Jones]

Hi John,
I suspect the blue component marked R32 is in fact a metal oxiide varistor. these are to protect the circuit from transients. I suspect this has failed almost short circuit causing the new 100 ohm resistor to fail. I think R32 is connected directly across the transformer primary. Can you photograph the etch side of the board and one of the new "100 ohm resistors" (So we can confirm that it is a 100 ohm resistor.) It is nice to be helping someone that is prepared to help themselves and answer questions about their problem. Too many posts start out something like "Tell me what to replace to fix my fridge" I will see if I can identify the varistor. (I think I will be able to read the part number as your pictures are so good.

Les.

 

[Les Jones]

Hi John,
I have found the datasheet on the device. It is a varistor. Farnell stock them. If it is connected in the way that I think it is then the board sould work with it removed but you should replace it to protect other parts. They are also sold on ebay. this is **broken link removed**.

Les.

 

[spec]

Hi John, Les has beaten me to it.

spec

 

[JohnMcC]

Hi Les and Spec,
Thank you for all your help. It is most appreciated.

I think R32 is connected directly across the transformer primary.

This is absolutely correct, it is.

The 5W100ΩJ is between one side of the primary (on one pin)................and the power wire ...........have tried to show all this in the attached photos.

For the Varistor...............I have marked 'Blue Component" in my photos !! Sorry !!!
Should I unsolder the Varistor from the board.............is there any way I can test it with a meter ?

It is nice to be helping someone that is prepared to help themselves and answer questions about their problem

That is the least I can do !

I think I will be able to read the part number

I have taken another photo for clarity.

Please refer to the photos, I have tried to make them as clear as I can

Many thanks,
John

 

[Les Jones]

Hi John,
You have already measured the resisistance (In post #15) of the varistor by measuring the resistance between the tracks that went to the transformer primary. You said that the reading was 300 ohms. As I can see nothing else in prrallel with the varistor this must be it's resistance. You can remove it and test it out of the board and if it is still reading 300 ohms it is faulty. (I have just tested the resistance reading of some similar varistors and they all read greater than 20 megohms.) I think if you replace the transformer and 7805 you will find that you get the regulated 5 volts output. The board is just the 5 volt power supply and relay with a driver transistor. In post#12 you say that the compressor still runs. I suspect that the relay on this board controls the power to the compressor. As there is no 5 volts the relay could not be energised so I think the contacts may have welded together on the relay. (Unless thy are normaly closed contacts which is umlikely.) Can you measure the resistance between the square pad under the relay with 4 pins comming through it (Directly below the word plug of power plug.) and the track just to the right of it. Do not test the board out of the freezer unless you feel confident working on a board with open live mains on it. If you have a low wattage (15 - 25 watt) mains bulb (Old fashioned filiment type bulb.) connect it in series with the live side of the mains to the board.

Les.