Tefal GV8962 Pro Express steam iron - no power

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

https://www.badcaps.net/forum/attach...9&d=1603871079
It looks like it is blown up when the high Voltage dump occurred.

Circuit ground for your probe will be the Negative leg of C2, then test Voltage on each leg of that U2.
It looks like the center pin is ground, if that is the case then will not be the same as typical 1117 regulator. You can verify if center pin is connected to circuit ground or not by checking the resistance between C2 negative leg and center pin of U2 to see if it shows <1 Ohm or not. You should also check the resistance of the two outer pins against ground.

If you cannot read the print then it will be hard to figure out what the output Voltage should be, it may rated as the same Voltage for the IC's VCC.

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

How do I check this U2?

I put DMM in Volt mode, put black on common pad, and Red on each lead:
Left one reads 23Vdc
Middle and Right ones read 0Vdc

*left side is bulged..

I just googled to learn more about LDO. If the picture is a correct pinout of a LDO, then it measured input is 23Vdc, and output is -0Vdc.

Does this mean this LDO is faulty/open?

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

You need to check Voltages of U2 which looks like LDO Regulator IC.

How do I check this U2?

I put DMM in Volt mode, put black on common pad, and Red on each lead:
Left one reads 23Vdc
Middle and Right ones read 0Vdc

*left side is bulged..

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

You need to check Voltages of U2 which looks like LDO Regulator IC.

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

At this point you can leave the 100 Ohms resistor for testing for now.
So the 24V buck converter is working now, now we need to trace out the other power supply section for low Voltage that is used for running those IC's (U3, U4) next.
So look up the part number of some of those IC's so you can look up the spec sheet to locate the VCC pin of the IC then you can find out if the VCC is present or not for the IC's to run.
Check Voltage of U2, it looks to be LDO Regulator IC.
I also see some bad solder joints, one looks burnt, others you can see ring developing around the joint, so look for ring around the solder joints and resolder them.
BTW, that small white connector, what is connected to that connector?

The black color that looks burnt is permanent black marker ink, on the the joints that have wired soldered directly onto. The ring around the solder joints - except for the huge wire joints with black marks, practically all the joints has some sort of indentation. Some looks like a ring, most are just dings. I re-soldered most of them.

I looked up for and these are the 2 ICs:
1) Top, bigger one: PIC16F1933: pin 19 & 20 measure 0.03Vdc
2) Bottom, smaller one: HC595A: pin 8 & 16 measure 0.03Vdc

Pressing power button on/off has no effect on the readings.

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

Arh... indeed, one end of R1 solder joint is done poorly.. Reworked, and now D pin & C1 (I believe not C4) get 325Vdc, and C2 gets 24Vdc.

But pressing the power on/off button still no led light..

*Noted on R1 being a 100 ohm resistor, should get a 2W 8-10 ohm replacement?

At this point you can leave the 100 Ohms resistor for testing for now.
So the 24V buck converter is working now, now we need to trace out the other power supply section for low Voltage that is used for running those IC's (U3, U4) next.
So look up the part number of some of those IC's so you can look up the spec sheet to locate the VCC pin of the IC then you can find out if the VCC is present or not for the IC's to run.
Check Voltage of U2, it looks to be LDO Regulator IC.
I also see some bad solder joints, one looks burnt, others you can see ring developing around the joint, so look for ring around the solder joints and resolder them.
BTW, that small white connector, what is connected to that connector?

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

You are not getting Voltage feeding the D pin of the IC, you need to check the Voltage between the two legs of main filter cap C4 (Green cap next to the resistor) first and also check your soldering works.
BTW, 100 Ohms is too high for that fusible resistor, but of testing purpose t is OK for now.

Arh... indeed, one end of R1 solder joint is done poorly.. Reworked, and now D pin & C1 (I believe not C4) get 325Vdc, and C2 gets 24Vdc.

But pressing the power on/off button still no led light..

*Noted on R1 being a 100 ohm resistor, should get a 2W 8-10 ohm replacement?

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

Yes, D3 no longer show 30ohm. It shows 532ohm in resistance mode, and 579 in diode mode.

C2 shows 0.1v and U1 shows 0.2v between Drain pin and each of all other pins.

Pressing the BP5 Power on/off button has no effect..

You are not getting Voltage feeding the D pin of the IC, you need to check the Voltage between the two legs of main filter cap C4 (Green cap next to the resistor) first and also check your soldering works.
BTW, 100 Ohms is too high for that fusible resistor, but of testing purpose t is OK for now.

[CapLeaker]

Re: Tefal GV8962 Pro Express steam iron - no power

does u1 get power from the resistor?

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

So now you are saying the resistance on C2 no longer show 30 Ohms?
Do you have 24Vdc on C2?
You also need to find out if you also have low Voltages to runs those IC or not

Yes, D3 no longer show 30ohm. It shows 532ohm in resistance mode, and 579 in diode mode.

C2 shows 0.1v and U1 shows 0.2v between Drain pin and each of all other pins.

Pressing the BP5 Power on/off button has no effect..

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

So now you are saying the resistance on C2 no longer show 30 Ohms?
Do you have 24Vdc on C2?
You also need to find out if you also have low Voltages to runs those IC or not

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

I decided to restore all the good and new components back into the PCB and do a basic continuity check - new 2W 100ohm R1 resistor, new 50v 100uF C2 capacitor, new U1 LNK304, and the original L2 inductor.

All pretty much the same, except now D3 now reads 579 in circuit.

I connect a 40W incandescent bulb between the Live wire of the incoming power. Power on - the incandescent bulb do not light up at all, the I measure to incoming voltage to the PCB - 243V.

But pressing the power button of the device - nothing happened, nothing blown, no led light.. Something component(s) blown opened?

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

Why don't you remove C2 and check it out of circuit, or remove it and check the solder pads to find out what is reading 30Ω

C2 already removed when it "exploded" on powered up.. but it still ready 89uF off circuit. The 2 solder pads between them ready 30ohm. I traced the +ve pad along the path to R31 and R31 read 120k ohm.

Not sure where to trace further...

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

Why don't you remove C2 and check it out of circuit, or remove it and check the solder pads to find out what is reading 30Ω

I would have thought he had removed that blown up cap already since it is blown up, if not then I do not understand why it is not removed.

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

D3 is basically in parallel with the load through the Low DCR of the Buck inductor, that is why you see 30 Ohms when D3 is measure in the circuit, look at the circuit of the Buck converter then you will understand why.

[R_J]

Re: Tefal GV8962 Pro Express steam iron - no power

Why don't you remove C2 and check it out of circuit, or remove it and check the solder pads to find out what is reading 30Ω

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

The buck converter looks to be set up for 24V output, you can verify that by checking the value of the feedback resistor network , that is why the blown up C2 is rated at 50V, twice the operating Voltage.
I would not pull the relay out, you should concentrate on what component are connected to + lead of that filter cap C2. if you check the resistance between the two legs of the filter cap c2 solder pads, what do you get, 30 Ohms?

Yes, both relays clicked when I applied 18v into them. And yes, the 2 solder pads of C2 reads 30 ohm.

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

the first 2 pictures show a 24v relay not a 12v, the 3rd pic the inductor. The inductor should be ok showing 1.8 Ohms.

Arh.. silly me.. Yes, I applied 18v and it clicks, both off and in-circuit.

With Inductor L2 removed, D3 measured correctly at 579 one way. When removed, it measured 30. Seems to by-passed to a shorted circuit somewhere?
-

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

I trace out the relay driver, the buck converter is set to 24V for the relay coils.
Transistor T2 drives the relay REL1

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

The buck converter looks to be set up for 24V output, you can verify that by checking the value of the feedback resistor network , that is why the blown up C2 is rated at 50V, twice the operating Voltage.
I would not pull the relay out, you should concentrate on what component are connected to + lead of that filter cap C2. if you check the resistance between the two legs of the filter cap c2 solder pads, what do you get, 30 Ohms?