KSGER STM32 V3.1S T12 blew smoke the moment I plugged it in

[AstutePauciloquent]

Hi everyone, I hope you're having a great day.

Such a shame as i've seen good things about this soldering iron. So yeah as the title says I got this soldering iron from the KSGER aliexpress store, plugged it in (240V NZ), as rated, and multiple components decided to turn crispy. The interesting thing i found was on the control board where pins 3 and 4 have a solder bridge, im wondering if anyone here has the same version of the soldering iron and can confirm if this solder bridge is normal or not. If im not mistaken the solder bridge seems to be bridging across where some version ground the control board, pin 4 is +. 

This is the solder bridge. My friend also brought one, that remains untested, and he also has the solder bridge, so im beyond confused.


Here we can see R1 is toast


R8 and the IC near it is also toast

[DavidAlfa]

That bridge is ok (Gnd + earth), likely the PSU blew apart because it's chinese crap.

[AstutePauciloquent]

That bridge is ok (Gnd + earth), likely the PSU blew apart because it's chinese crap.

Hi are you sure, because its actually GnD to +24V. This bridge creates a 0 Ohm short between +24V the adjustment control switch.

Right before this unit blew up, it had a large ERROR message on the screen (I remember). So I hooked it up to my voltage injection PSU with 5V and a limit of 1A and it powered on with the same large error message. I did the same thing but i removed the solder bridge, and the error message had disappeared, and it began to heat up, before complaining about the low voltage I was using.

[DavidAlfa]

Nah, it's fine.
Look how every Ksger V2/V3 board has these pins connected together:
https://github.com/deividAlfa/stm32_soldering_iron_controller/blob/master/Readme_files/boards.md

Here's your board with the same bridge:
https://github.com/deividAlfa/stm32_soldering_iron_controller/blob/master/Readme_files/boards.md#bad-ldo-design-read-ldo-issues-4

[floobydust]

Get a refund or a new power supply. It's a lot of work to fix these. The mosfet shorts, SMPS IC shorts, resistors blow and the fuse does not lol.
Is it a V2.04 or V2.05 PSU? What version?

[AstutePauciloquent]

Nah, it's fine.
Look how every Ksger V2/V3 board has these pins connected together:
https://github.com/deividAlfa/stm32_soldering_iron_controller/blob/master/Readme_files/boards.md

Here's your board with the same bridge:
https://github.com/deividAlfa/stm32_soldering_iron_controller/blob/master/Readme_files/boards.md#bad-ldo-design-read-ldo-issues-4

Pin 3 on that plug is the Gnd pin for the hand piece, when the hand piece is plugged in to the unit, this bridge creates a short from the outer metal of the hand piece to the current going to the heating element inside the tip. Please explain how this is fine, and why my power supply blew up because of it.

[floobydust]

Pin 5 is the heater output(+) which is the only pin that can cause blowups if shorted to GND.
Why do you think pins 3 or 4 are to blame? You might have a handle wired incorrectly.

[AstutePauciloquent]

Get a refund

LOL Yeah they really are amazing rubbish. I guess i got duped into buying one from youtube and others. My PSU version is V2.05

They reluctantly honored my refund, yesterday. And i foolishly ordered another, thinking that what happened to me was rear, but it seems this is not the case.

[DavidAlfa]

The outer metal is protective earth. This bridge joins psu ground and PE. Nothing wrong with it.
I bet you didn't even try looking at the boards page I linked.
Every Ksger has those two pins bridged, either by solder or in the PCB itself.

[AstutePauciloquent]

The outer metal is protective earth. This bridge joins psu ground and PE. Nothing wrong with it.
I bet you didn't even try looking at the boards page I linked.
Every Ksger has those two pins bridged, either by solder or in the PCB itself.

Yes you are indeed correct, I did check the page you linked. Please accept my apology

So where the +24V going into the control board in my picture, is actually meant to be -(negative) ?

[DavidAlfa]

Nope, seems reversed? The - should go to pin 4 /T-, and the positive to the transistor.

[AstutePauciloquent]

Nope, seems reversed? The - should go to pin 4 /T-, and the positive to the transistor.

Well I guess we know why my PSU blew up.

This is why i was confused, I just thought the wiring was correct from the factory. But then again I should have noticed huge ground plans are not usually +Positive LOL. My bad
It was the plug being wired incorrectly all along, leading me to believe that Pin 4 was the +24V side.

So sorry everyone, can we still be friends?

[Veteran68]

Yeah that 4409 is a P-channel FET so I'd expect the + to go to the source as DavidAlfa drew it. Plus the other pin connects to what looks like a big ground plane. I'd say the wires were reversed at the factory. QA for the win!

[DavidAlfa]

Still, the PSU shouldn't have blown up this way, must have overload protection.
Before wasting your time, make a claim to the seller right away, it's a factory defect.

[AstutePauciloquent]

Yeah thanks mate, the refund was approved yesterday.

[AstutePauciloquent]

I did some inspection and noticed the FQPF20N60 N-Channel Mosfet looks to be faulty, shorted, or fake? Drain-Source reads as shorted, but the component tester detects it as a dual resistors.

Edit: According to a reddit post i found, this means the mosfet is dead. I'm yet to know if this blew, as a result of the polarity being crossed, or if it was faulty right from the start and was the cause of the PSU blowing.

[elektryk]

I'm yet to know if this blew, as a result of the polarity being crossed, or if it was faulty right from the start and was the cause of the PSU blowing.

Good SMPS should be protected against output short circuit, but in this case it might be the reason.
If you still want to repair it, just check controller board with an external power supply.

[AstutePauciloquent]

Yeah ive tested the controller board and oddly it works 100% I've ordered all the components I need to repair the PSU. Me and a friend researched the value of the Zener diode, that's no-longer a diode at all. it's an 18V Zener, according to the datasheet for the CR6842S PWM Controller that sends the gate voltage to the FQPF20N60C Mosfet. I'm looking forward to repairing it.

[floobydust]

There is no zener diode that I know of. Schematic for KSGER V2.05 PSU over here.
The SMPS mosfet is dead, shorted. Also dead would be 0.3R resistor, gate drive resistor R13+diode D6, did it blow the fuse lol.
Your R6 and R8 maybe R10 are also dead so the IC is blown and sometimes the 22uF cap and opto-coupler get killed too.
It can be less cost and hassle to toss it in the garbage and buy a new one.

edit: Be careful working with this, there are no bleeder resistors so the primary-side cap can have a charge on it and bite, if there is nothing to leak current out of it, IC blown.

[AstutePauciloquent]

There is no zener diode that I know of.

So D6 is not a Zener? I wonder what it is and the value it could be.

[floobydust]

My opinion, black band D6 is a MELF diode 1N4148 for the power mosfet gate-drive to turn it off fast. A DL4001 is too slow. Could use a S1A or any fast diode in a plastic package.

[AstutePauciloquent]

My opinion, black band D6 is a MELF diode 1N4148 for the power mosfet gate-drive to turn it off fast. A DL4001 is too slow. Could use a S1A or any fast diode in a plastic package.

Thanks, I had no idea there where many different types of MELF diodes. I just though these small glass shaped ones where all zeners. I also discovered the CR6842S datasheet was talking about an internal 18V Zener, thats inside the CR6842S IC. It's costing me more to repair this than it is to buy a new one, but im not doing this to be cost effective, im doing it to learn these types of things. (And ive already ordered a new one)

[BlackICE]

Can you get a replacement or refund? I have 2 of these. One with a PS and another just a controller board I connect to a 24V power tool battery for portable use. As with most low cost things from China, QC is lacking and getting a good working one is a crap shoot.

If you get one that works well they perform much better than a Hakko 888 or Weller 1010NA. Both of which cost much more.

[AstutePauciloquent]

Can you get a replacement or refund?

Yes I got the refund, and I also ordered another one. However, I can't believe my eyes right now.

This is a photo of my new iron I got delivered today +Positive lead is going into the -Negative input on the control board, same issue i had above. I'm extremely happy that i took this one apart before plugging it in. However If i got two in a row with this fault, how many other unsuspecting customers are being sent incorrectly wired devices?

[BlackICE]

Sometimes it's difficult to find Qualified workers at a prison camp.