Tefal GV8962 Pro Express steam iron - no power

[Wim Smits]

This is a picture of the chip, the text is LA7A. Which chip is it?

[Wim Smits]

I checked this story since I have the same problem. I removed U1 and applied 24 volt from a power source to C2. I first limited current and increasing current flow I feel U2 heating up so I think this regulator? is defect. I read LA7A or 1A7A on the component U2. Which component is it?

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

I have already removed C7 and the resistance remains unchanged at 20.8Vdc. I have also attempted to trace and measure all the caps an resistors leading to the Vcc of the 2 ICs. Not surprisingly, I do not know what I was doing... But I feel the resistance pretty much measured 20.8Vdc in most places along the trace.

I reckon that this would not go very far to determining what else is faulty beside the now apparent U2 being blown opened. But suffice to say replacing the R1 with a 5W 100 ohm was a MAJOR MISTAKE!! Nonetheless, it has been very educational, and I want to thank you (and CapLeaker) once again for patiently guiding me alone this learning journey.

Thank you.

At least you gin the knowledge. One of the weak point of Buck converter is that when the pass device (I.E. MOSFET) shorted out, the input Voltage will be dumped into the load and can cause lots of damaged, they should at least put crowbar and a fuse on the output.

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

So pin1 of U2 is the Output pin for feeding VCC for the IC's.
You can try removing C7 first to see if the resistance will go up or not, there are also other filter caps connected to this VCC line that have to be checked, worst case will be that the IC's are damaged.

I have already removed C7 and the resistance remains unchanged at 20.8Vdc. I have also attempted to trace and measure all the caps an resistors leading to the Vcc of the 2 ICs. Not surprisingly, I do not know what I was doing... But I feel the resistance pretty much measured 20.8Vdc in most places along the trace.

I reckon that this would not go very far to determining what else is faulty beside the now apparent U2 being blown opened. But suffice to say replacing the R1 with a 5W 100 ohm was a MAJOR MISTAKE!! Nonetheless, it has been very educational, and I want to thank you (and CapLeaker) once again for patiently guiding me alone this learning journey.

Thank you.

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

The resistance of those 2 ICs are both 20.8 ohm. After removed C7, same reading.

Yes, indeed it will be purely academic from now on. And if there is any further fault finding worthwhile, it can only be done with SMD removal, and not restoring as I am not equipped and not capable.

At this juncture, I want to thank you both, BUDM and CapLeaker, for spending time coaching me. It's been a pleasure learning under your coaching.

Thank you very much.

So pin1 of U2 is the Output pin for feeding VCC for the IC's.
You can try removing C7 first to see if the resistance will go up or not, there are also other filter caps connected to this VCC line that have to be checked, worst case will be that the IC's are damaged.

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

I am talking about the two IC's that you found the spec sheet to get the VVC pins, check the resistance of those VCC pins.
BTW, since you cannot do SMD repair so it is a moot point to keep trying to fix the board.

The resistance of those 2 ICs are both 20.8 ohm. After removed C7, same reading.

Yes, indeed it will be purely academic from now on. And if there is any further fault finding worthwhile, it can only be done with SMD removal, and not restoring as I am not equipped and not capable.

At this juncture, I want to thank you both, BUDM and CapLeaker, for spending time coaching me. It's been a pleasure learning under your coaching.

Thank you very much.

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

I think C7 may be shorted too. Take it out and remeasure it out of circuit.

I took out C7 - off circuit fluctuated between 3.8 - 14 uF, probably the contact points are somewhat damaged... The resistance between the 2 C7 pads reads 20.8 ohm, same reading with the C7 in circuit.

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

I am talking about the two IC's that you found the spec sheet to get the VVC pins, check the resistance of those VCC pins.
BTW, since you cannot do SMD repair so it is a moot point to keep trying to fix the board.

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

Now check the resistance between GND and VCC pins of the IC's.

Hmm.. I missed out the most devastating part when remove U2 without the right tools - the black material cracked into pieces when I tried hard to remove it with a soldering iron and a tweezer...

So, ya, can't do any test on U2

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

I think C7 may be shorted too. Take it out and remeasure it out of circuit.

OK, I think it will mostly likely be a destructive removal..

[CapLeaker]

Re: Tefal GV8962 Pro Express steam iron - no power

I think C7 may be shorted too. Take it out and remeasure it out of circuit.

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

I removed U2 (I don't have a proper tools and skillsets, and damaged Pin3 pad).

With U2:
C6: 178 ohm / 0L on capacitance
C7: 14 ohm / 0L on capacitance

Without U2:
C6: 539 ohm / 103 uF on capacitance
C7: 20.8 ohm / 0L on capacitance


** Pin1 resistance now 20.8 ohm vs 14 ohm previously.

Now check the resistance between GND and VCC pins of the IC's.

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

C6: 178 ohm / 0L on capacitance
C7: 14 ohm / 0L on capacitance

U2 does looks and feels bloated on the Pin1 side.

I removed U2 (I don't have a proper tools and skillsets, and damaged Pin3 pad).

With U2:
C6: 178 ohm / 0L on capacitance
C7: 14 ohm / 0L on capacitance

Without U2:
C6: 539 ohm / 103 uF on capacitance
C7: 20.8 ohm / 0L on capacitance


** Pin1 resistance now 20.8 ohm vs 14 ohm previously.

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

As shown in your picture: Pin 1 (Right pin) of U2 is connected to C7, Pin 3 (Left pin) is connected to C6.

I do not understand why your readings show Voltages. Are you checking the resistance of C6 and C7 with POWER applied to the unit while doing resistance test?

Sorry for not stating it clearer, I powered on to read voltages, and powered off to ready resistance, and recorded them in the same row..

So my reference of Pin1 & Pin3 is reversed. Based on your picture:
Pin3: 23 Vdc / 146 ohm
Pin2: < 1 Vdc / < 1 ohm
Pin1: < 1 Vdc / 14 ohm

Black probe on Pin2: Red probe on
Pin3: 23 Vdc / 152 ohm
Pin1: < 1 Vdc / 14 ohm

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

Black probe on C2 -Ve, Red probe on
Pin1: 23 Vdc / 146 ohm
Pin2: < 1 Vdc / < 1 ohm
Pin3: < 1 Vdc / 14 ohm

Black probe on Pin2: Red probe on
Pin1: 23 Vdc / 152 ohm
Pin3: < 1 Vdc / 14 ohm

Marking on U2 is completely not readable.

*** Just to be clear: Pin1 is on the left and Pin3 is on the right of the picture I attached.

As shown in your picture: Pin 1 (Right pin) of U2 is connected to C7, Pin 3 (Left pin) is connected to C6.

I do not understand why your readings show Voltages. Are you checking the resistance of C6 and C7 with POWER applied to the unit while doing resistance test?

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

BTW, look real close at C6 and C7 soldering joints connected to U2 pin 1 and pin 3, they do not look right.

Pin1 to C6: < 1 ohm
Pin1 to C7: 210 ohm

Pin2 to C6: 180 ohm
Pin2 to C7: 15 ohm

Pin3 to C6: 210 ohm
Pin3 to C7: < 1 ohm

[beetle1303]

Re: Tefal GV8962 Pro Express steam iron - no power

The LDO looks blown up to me. Check C6 & 7 for short and check the capacitance.

C6: 178 ohm / 0L on capacitance
C7: 14 ohm / 0L on capacitance

U2 does looks and feels bloated on the Pin1 side.

[beetle1303]

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.

Black probe on C2 -Ve, Red probe on
Pin1: 23 Vdc / 146 ohm
Pin2: < 1 Vdc / < 1 ohm
Pin3: < 1 Vdc / 14 ohm

Black probe on Pin2: Red probe on
Pin1: 23 Vdc / 152 ohm
Pin3: < 1 Vdc / 14 ohm

Marking on U2 is completely not readable.

*** Just to be clear: Pin1 is on the left and Pin3 is on the right of the picture I attached.

[CapLeaker]

Re: Tefal GV8962 Pro Express steam iron - no power

The LDO looks blown up to me. Check C6 & 7 for short and check the capacitance.

[budm]

Re: Tefal GV8962 Pro Express steam iron - no power

BTW, look real close at C6 and C7 soldering joints connected to U2 pin 1 and pin 3, they do not look right.