KSGER C245 Soldering station PSU 220V only?

[mkbehbeh]

I purchased this soldering station when it was on sale at amazon. It had a slew of one star reviews, but the price was low enough that even if the controller and PSU were toast, the handle tips and stand were worth more than the price. All of the reviews mentioned that the unit was either DOA, or died on the first use. I looked on Aliexpress and the first clue was that KSGER still sold the 220V version of this station, but all of the 110V versions had been discontinued. I figured That there was a problem with the 110V on the power suppply and the controller would be fine.

I am posting everything about the station here, in the case that some of the experts can weigh in on whether there is an easy fix to run the PSU On 110V or if it’s a lost cause, and what testing that I need to do to determine which is the case.

What I did so far:
I broke in tip separately and added solder

1. Powered up with only controller and no handle (worked)
2. Powered up with controller and handle in station (sleep mode, worked)
3. Lifted handle to heat up to set point of 150C and POOF!
4. Found the PCB mounted fuse was blown (3A) external 5A fuse was OK
5. Shorted the 3A fuse using current meter set on max mode plugged in controller and read 1.8A before blowing 5A fuse
6. Probing around I found that the MOSFET on Q1 was a dead short between S-D and S-G

Removed the MOSFET at Q1 and confirmed the MOSFET is dead. My next step is to see if I can power the controller on the bare board with DC only 1t 18V and see if it works.

Am I on the right track? What else should I check?

Thanks,
Mark

[mkbehbeh]

Here are the components that I could read
Selected Components:
R1 Inrush NTC 5D-11

BD1 Bridge rectifier GBU 808

Q1 MOSFET?? F 20B
FQPF
10N60C

U1 873A
LOUV

U2 Opto isolator FL
817C
F118

D1 MB
3020
ON (semi)
NE

Q2 431 voltage ref 431

Thanks,

Mark

[Swainster]

This looks like a universal input power supply, so by rights, it should operate from well below 100VAC to over 250VAC (or even DC) without problems.

Assuming that your 18V alternative supply works out (actually, the pic I saw indicated that the DC was supposed to be 24V), then it might be worth just trying a replacement Q1 - china supply chains suffer from a lot of counterfeit parts - this catches out the local manufacturers as well. That said, U1 might also be toast, but these are readily available from Aliex for a few dollars. If I were you, I'd probably try to source the Mosfet locally though.

Just noticed that it's a 150+W controller - your 18VDC supply should probably have at least 10A output.

[mkbehbeh]

I did manage to power the controller chip at U1 using 16v.  At first I thought I had killed the gate driver, but it turns out there is some protection mechanism if it is not seeing the rest of the inputs behaving normally.

The solution was to hook up all of the probes to the oscilloscope and set the trigger then power the controller chip.  It pulses the gate for a few cycles then stops.  The controller is powered from a separate coil on the main transformer and I was able to supply 16v across the capacitor.

Looking closely at the board,. They seem to have hacked on an inductor to the back in place of the current sense resistor in the reference design.

I've ordered the MOSFET and an improved spec MOSFET so waiting on those to arrive.

As a more general question, is the max output higher from 220 vs 110?  The current on the primary side would need to be double for the same power.

[Swainster]

As you say, to maintain a certain power level then the input current would be higher for a lower input voltage, but I wouldn't have thought that this would blow Q1... unless it was fake. I'm more of a power supply user than a designer, but when evaluating new supplies, I've never yet blown one up by running at too low an input voltage.

I think that 'inductor' is just a fusible resistor i.e. it is the current shunt, just moved to the other side of the board - perhaps to prevent it heating up the nearby electrolytic.

[mkbehbeh]

As you say, to maintain a certain power level then the input current would be higher for a lower input voltage, but I wouldn't have thought that this would blow Q1... unless it was fake. I'm more of a power supply user than a designer, but when evaluating new supplies, I've never yet blown one up by running at too low an input voltage.

I think that 'inductor' is just a fusible resistor i.e. it is the current shunt, just moved to the other side of the board - perhaps to prevent it heating up the nearby electrolytic.

I did get it working and Ill post details later, but I finally got a nice explanation for the 110V vs 220V behavior.  The magnetic flux generated is a function of the volts per turn on the coil.  The maximum saturation is a function of magnetic flux.  So while the 220V needs less current for the same flux (and power transfer), the saturation limit is also half as much.  The 110V needs more current, but the saturation limit is 2x higher so it all washes out.