Tefal GV8962 Pro Express steam iron - no power

[beetle1303]

Originally Posted by budm

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..

[CapLeaker]

does u1 get power from the resistor?

[budm]

Originally Posted by beetle1303

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.

[beetle1303]

Originally Posted by budm

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]

Originally Posted by beetle1303

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]

Originally Posted by budm

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]

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

[beetle1303]

Originally Posted by budm

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..

[beetle1303]

Originally Posted by beetle1303

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?

[budm]

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.

[budm]

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

[CapLeaker]

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

[beetle1303]

Originally Posted by budm

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.

[beetle1303]

Originally Posted by CapLeaker

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]

Originally Posted by budm

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

[budm]

Originally Posted by beetle1303

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]

Originally Posted by budm

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

[beetle1303]

Originally Posted by beetle1303

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.

[budm]

Originally Posted by beetle1303

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.

[CapLeaker]

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