KSGER T12 mini Soldering Station DOA

[michalism]

Hello.
I have recently bought this "famous" soldering station from Banggood, but unfortunately it's totally dead - non-responsive by any means.
I'm in the process of claiming my money back from Banggood, but in the mean time, I would like to see if it can be fixed.
Below is the link to the system I bought;
https://www.banggood.com/KSGER-MINI-V2_01-T12-Soldering-Station-with-XA-Grade-T12-K-Electric-Soldering-Irons-Tips-p-1407447.html?rmmds=myorder&cur_warehouse=CN

it comes with an external power supply, which seems to be in working condition. I have tried my workbench PSU, and the unit still does not power up.

Any chance I can find the schematic?
A nice guy from Portugal has reversed engineered what I think is a previous HW version of this station, and I am trying to use it for reference, without much luck so far.
Link here:
https://www.ptdreamer.com/chinese-stm32-oled-soldering-controller-reverse-engineer-custom-firmware/

What I noticed is that U2 (JWBH) which is a step-down converted, does not get any power at all. It should have 24V on pin 6, but it is at ~0.8V.
Not sure what to check. All the passive components that I see associated with U2 check OK (in circuit).

Any advice would be much appreciated...

Regards,
Michalis

[bob91343]

See if IC1 is good.  It looks like a regulator.  Also D1 might be shorted.

[michalism]

Hi.

D1 was checked in circuit, seems good.
Sorry, I can't find IC1. If you refer to the 8-pin IC to the right of the picture and below the electrolytic, that's a mosfet TPC8111 and also seems to be working fine.

[Chris56000]

Hi!

Is there any identification or type number on the board? I've been looking for a board of this type to purchase for drawing–out purposes!

Chris Williams

[bob91343]

IC1 is a three terminal device top center in the diagram.

[michalism]

IC1 is a three terminal device top center in the diagram.

ok, you mean the schematic; sorry, I was looking at the images.
IC1 does not seem to be present on the board I have.

 

Hi!

Is there any identification or type number on the board? I've been looking for a board of this type to purchase for drawing–out purposes!

Chris Williams

no, sorry I can't find any id. Maybe on the other side, but I am still struggling to unsolder the connector to remove the pcb

[floobydust]

There's many different T12 clone controller boards. KSGER controllers are higher quality than OP's.

This is another Banggood one with design issues, a rogue copy. They can't seem to do a reliable 3.3V regulator design and many are failing.

[floobydust]

SMD marking JWBH SOT23-6 is for part JW5026.
JoulWatt 40V 1A 1.1MHz buck converter with built in mosfets and sync. rectifier, so no buck diode to be seen.

[Hemi345]

@michalism, pin 5 of U2 should have 24V on it, not pin 6.  Recheck diode D1.   Otherwise, I'd suspect U2 is bad as well.  I don't believe KSGER is providing enough heatsinking via trace width for the vreg as that was the issue with my first controller.

TI's TPS560430 simple switcher looks to be pin compatible with U2 although you'll need to adjust the values of feedback resistors R3 and R6 and potentially inductor L1.

[floobydust]

OP, what were you doing with electrolytic capacitor C13?  A bigger part will overload diode D1 due to inrush currents and could have killed it.

[michalism]

@michalism, pin 5 of U2 should have 24V on it, not pin 6.  Recheck diode D1.   Otherwise, I'd suspect U2 is bad as well.  I don't believe KSGER is providing enough heatsinking via trace width for the vreg as that was the issue with my first controller.

TI's TPS560430 simple switcher looks to be pin compatible with U2 although you'll need to adjust the values of feedback resistors R3 and R6 and potentially inductor L1.

you're correct, pin5 is Vin, I just mistyped the number.

I have found all components on-line and thinking to order a few and replace them; however, I'd like to see if I can find the problem instead of randomly swapping components

OP, what were you doing with electrolytic capacitor C13?  A bigger part will overload diode D1 due to inrush currents and could have killed it.

I have removed the original capacitor to check and then replaced it with another of same characteristics. I have put the original back now.

[Hemi345]

@michalism, pin 5 of U2 should have 24V on it, not pin 6.  Recheck diode D1.   Otherwise, I'd suspect U2 is bad as well.  I don't believe KSGER is providing enough heatsinking via trace width for the vreg as that was the issue with my first controller.

TI's TPS560430 simple switcher looks to be pin compatible with U2 although you'll need to adjust the values of feedback resistors R3 and R6 and potentially inductor L1.

you're correct, pin5 is Vin, I just mistyped the number.

If Pin 5 only has 0.8V, then D1 is bad or the polarity on the 24V input header is reversed?  You could try providing 24V using your bench power supply to the legs of C13 to bypass D1.  Make sure you wait at least 5 seconds after giving it power as sometimes it takes a few seconds for the station to show signs of life. 

Side note, the soldering job on the handpiece aviator connection looks pretty poor.  If you manage to get that controller working again, I'd touch those up for a better connection as well as soldering the retention clips on the rotary encoder.

[michalism]

@ Hemi345: The input header seems to be ok, since the GND and 24V+ pads on the pcb have the correct polarity when I check with the multimeter.
                   I wanted to try injecting 24V to C13 or R21 (104) or to U2 directly, but I wanted to ask if this is a good idea first.

[michalism]

Hi again.

I have supplied 24V at the positive leg of C23 and the unit powers up. With the handle not connected it shows "ERROR" which is normal.
When I connect the handle, after a few seconds the message "INVERT" shows up and the beeper sounds. The iron is not warming up and the current draw is around 0.01A. I tried two different tips to rule out a faulty tip.

From a quick search on-line, it looks like some others had a similar issue and it was resolved with another board. However, I am not convinced this is the case for me.

On my board, there is an SMD LED (D4) which is not lit when I power the unit up; I suppose this is not normal, is it?

Any ideas what to look for?

[michalism]

UPDATE:

well, the JW5026 is officially roasted!
When the system is powered on, if you pay attention you can hear a high pitch hissing sound. I am not sure if I use the right word, but it is similar to the noise a transformer does sometimes. The volume is very low, you really have to put your ear close to the board to hear it.
I assumed that this may be some kind of an oscillation, so I used my scope to see if I can find anything. The first point I checked was pin6 of JW5026, which is its output. Sure enough, the waveform looked like an EKG, with one huge peak at around 6-8 V and two smaller ones at around 2-3V. Unfortunately, after a few seconds and before I was able to do any tracing, the IC started smoking so I cut the power.

Is there a chance that I accidentally caused the IC to die when I placed the scope probe on? The reason I am asking is that the magic smoke came out now, but I was able to operate the station for several minutes the previous days while poking around with my multimeter. It's hard to believe this is a coincidence

In any case, I am about to order a bunch of JW5026, replace the old one and keep trying.

Regards,
Michalis

[floobydust]

JW5026 pin 6 SW is supposed to have pulses there and the x1 scope probe adding a capacitive load there might be what killed it. Need a new IC.

I would make sure the buck-converter has enough capacitance, this tends to get minimized and cheapened to the point things barely work. The squealing/hissing can be instability in the buck-converter due to insufficient capacitance.

4.7-10uF 50V ceramic cap at the input, and 10uF at the output the datasheet recommends.
C13 electrolytic does not help much at 1.1MHz. C8 might be it but a long PCB trace, and C1 looks odd, I can't see where it connects.
C6, C6 at the output, I would make sure it's big at least 10uF there.

I see R20 and it's the resistor that kills the battery, I'm not sure why it's there.
This is the schematic of T12 V2.1 (no S) buck-converter section. V2.01 is LDO, V2.1S has JW5026 and pump mosfets.
edit: fixed filename

[Hemi345]

Hi again.

I have supplied 24V at the positive leg of C23 and the unit powers up.

So you applied power to C13 (I don't see a C23 in your pics) and the unit powered up?  That leads me to believe the power supply in the station is defective or D1 is bad. 

On my board, there is an SMD LED (D4) which is not lit when I power the unit up; I suppose this is not normal, is it?

Any ideas what to look for?

D4 only illuminates when the station is supplying power to heat the tip, if the station is sleeping or the handle isn't connected, mine didn't light up.  Make sure you push the tip all the way into the handle.  With the FX9501 handle on mine, I'll feel it 'click' twice as I'm sliding the tip in.  Showing 'INVERT' on the screen makes me think you didn't push the tip all the way in.

If you want to keep playing around with the station while waiting for the new switchers to come in, you can inject 3.3V from your bench supply into the header for the OLED above D1 (the first two pins on the right side with fat trace and groundplane are ground and 3.3V).

[ornea]

So did this get resolved. 

My D1 also has ~0.8 volts across it. It seems to vary a bit ~0.7V -1.2V

Bridged over D1 with a 1n4004 and so far so good.

Thanks for the tip and schematics in this post.  Makes diags so much quicker and easier.

[Dickysoe]

Hi,
JWBHJ on my T12-X burnt, there is a burnt mark on the top of the IC.
But I cannot find JWBHJ nor JW5026 anywhere here in Indonesia.
Can anyone please help me with alternatives?
I browsed marketplaces, and managed to find similar items like :
MP2359DJ
TLV62565
MP2456
SY8120B1ABC
MP1470GJ (pin to pin  order different)
MP2451DT
AOZ1282CI
STI3407

Is any of those compatible?
Really need your advise.
Thank you All.