T12 STM32 V2.1S Soldering Station Controller - schematic etc.

[yelkvi]

Here is a diagram of your board (or similar):

[Enric]

on the point 1, read 24V
on the point 2, read 0V
and the chip "3" is a very small, with a magnifying glass I read "jwbmj 9ya4l" but doesn't found nothing on the internet.

[Enric]

Great, I think this is the one that is dead since I don't read 3.3V at the output, what can I do?

[yelkvi]

Chip "3" is a DC/DC step down converter. Looks like JW5026 (datasheet for it in the file).

Pins "5" and "4" should have an input voltage of 24 volts. And after the inductor "L1" - 3.3V.
If there is no voltage 3.3, then several options are possible:

1. Closing the circuit after "L1". To check this, you need to measure the resistance from the "L1" coil to "-".
2. The breakage of the coil itself - measure its resistance - should be almost "0".
3. Bad soldering - carefully look through all the small radio components around this microcircuit under a magnifying glass.
4. The chip itself is faulty - it needs to be replaced (if there is no JW5206, then pick up an analogue).

[Enric]

okey!
in the pass nº1 I measure 0.6Ohm without voltage.
2- 0.8 ohm
3 i iew all ok
4 the most possible.
is possible put a 3.3V with an external power supply? to make it easier, can I connect it to the vcc of the display?
If it worked like this, could you remove the chip and put a 3.3V AMS117? I know the footprint doesn't fit but I could mount it on another plate or aerial.

[DavidAlfa]

Now remove the coil and check at which side the short is.
Could be just bad capacitor.

[yelkvi]

2- 0.8 ohm

This is not good. Very little.
I read one topic on a Russian site. Many users had a problem with a soldering station, where the 3.3 voltage regulator is made like yours. I'm sorry, but the STM32 chip itself failed.
If possible, unsolder the controller. If the resistance increases, then the STM.
Moreover, they wrote on that forum that the stabilizer microcircuit was also out of order.
Most likely, at first it failed, and then 24 volts entered the STM.
To make the circuit more reliable, the step down converter must be set to 5 volts, and after it, set 1117 to 3.3V

[Enric]

Ok, tomorrow I'm going to go find another welder and I'm going to try it.
Thank you all very much.

[floobydust]

Best to start a new repair thread for your controller. The JW5026 appears to be sole-sourced, I did not see any alternate part.

[yelkvi]

If you are going to buy a new STM32F103 chip, then pay attention that you need it with 64 pin (16 pin on one side). Because there are 48 pins (12 pins per side).

[Dickysoe]

Hi All,
I'm not very good in electronics. And i got a JWBHJ chip burnt uon connecting to 6S lipo battery.
Can you please help me find a direct replacement for JWBHJ or JW5026?
I cannot find them anywhere here in Indonesia.

[yelkvi]

The JW5026 is a current mode monolithic buck switching regulator

[Dickysoe]

Yes, i was looking for alternatives. But don't know which one available in my country.
I tried purchasing AOZ1282CI & MP2451DT. Hopefully those 2 IC can be used. They have the same package SOT23-6 and pin order.
Can you please help me, i need information whether those 2 IC can be used or not.

[DavidAlfa]

You need to ensure few things:
- Same pinout.
- Similar current and input voltage capabilities.
- Similar switching frecuency.
- Same reference voltage, but not really critical as long as  you replace the feedback resistors to match the same output voltage.

[yelkvi]

If these microcircuits are not available in your country, then you can buy them on Aliexpress. They are there. Inexpensive.

[Dickysoe]

Hi thank you for your reply.
I just bought today some that might be compatible. Can you please help me choose the safer bet to replace JW5026?

JW5026
- monolithic buck regulator
- 4.7V to 40V
- 1A output current
- Output 0.8V to Vin-3V
- 1.1 MHz switching freq

and I bought 3 types :

AOZ1282CI (SOT23-6, same pin layout as JW5026)
- High Freq Buck Regulator
- 4.5V to 36V
- 1.2 A cont output current
- 450 KHz PWM operation
- output voltage adj to 0.8V to 0.85*Vin
- 420 mOhm Mosfet

MP2451 (SOT23-6, same pin layout as JW5026)
- High Freq step down switching regulator
- 2.2V to 36V
- 0.6A high efficient output
- 2MHz switching freq
-  Adj output 0.8V to 0.8*Vin
- 500 mOhm mosfet

MP2456GJ (SOT23-6, same pin layout as JW5026)
- Monolithic switch step down converter
- 4.5V to 50V
- 0.5A output
- Fixed 1.2 MHz freq
- adjustable output 0.81V to 0.91*Vin
- 1 Ohm mosfet

Thank you for your help.

[Dickysoe]

Just checked on Aliexpress.
they cost in lot of 10 pcs.
not expensive. but the shipping is so expensive, let alone the Indonesian import tax, which is quite high based on my experience on servicing under warranty to fatshark goggle Australia. they charged me a lot of money.

[DavidAlfa]

I think any of these would work.
I'd probably start with the MP2451, the increased frequency shouln't be an issue.

[Dickysoe]

Will try it as soon as it arrived.
Thank you so much for your help and advise.

[DavidAlfa]

An advice: Try isolating the output, so it doesn't fry everything if it sends 20V instead of 3.
However it must be done after the coil and the first capacitor, what's your board?

[Dickysoe]

i looked at the diagram for 3.3V for each, and notice that I need to change 2 resistors :
one  between SW and FB pin and another one between FB and GND pin
all the ICs have different value of resistor compared to JW5026.
I cannot find the board diagram anywhere on the internet.
but assuming from the datasheet table for 3.3V, I need to to change 2 resistor i doddle with yellow on the pics in order to get 3.3V output.
am I correct?

[DavidAlfa]

Not si critical as long as the relation is the same.

[Dickysoe]

So, is it OK if I just replace JWBHJ with other buck converter IC only? The output voltage should be read on SW pin?

[DavidAlfa]

No, it's a switching regulator (SW makes 24V pulses) the voltage will be seen at the output of the coil, measure at C4 (the side with a line mark)

[Dickysoe]

Will try changing the IC tomorrow. Thank you for you help. Hopefully nothing blow up tomorrow.