Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

[MyBrainIsAStrainer]

Hello! I'm newbie-ish in electronics and hope you can help me.

I use a Quicko (or Quecoo, not sure which is correct) T12-955 soldering station as my daily driver. Recently, I had a mishap. While changing tips, the metal contact inside the handle got bent and must have shorted against some other contact. Since then, the station only shows "Error" on its display. I fixed the bent contact but the error didn't go away. In fact, now it's completely dead.

After opening it, I found obvious two faults: A chip that looked molten (U5), and another chip which got very hot when applying voltage (U1). I would like to replace both and see where that gets me.

I managed to identify U5, even though the writing is gone. It appears to be a LD1117AG 3.3V voltage regulator. But I have no clue what the other chip is. It is labelled "W539". I'm not sure about the footprint, I think it's called SOT23-6. I tried googling, but came up empty.

I also couldn't find any schematics. There's a partial here but it doesn't seem to match my board.

Does anybody know what this component is? Or do you have any schematics?

[R_J]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

U1 is likely a R5325N005B

[stj]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

the 6pin device is a buck convertor,
it drops 24v down to about 5v to feed the display, then it feeds the 1117
that generates 3.3v for the logic.
it's *very* similar to the ksger v2.1 unit
u1 could be a JW5026

i dont see how shorting the switched 24v to ground or the sleep-input could have done that!

[MyBrainIsAStrainer]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

First of all: Thanks to both of you for replying!

U1 is likely a R5325N005B

I looked at the data sheet I got from here, and I think the pinout does not match.

The data sheet says that ground should be on pin 5, but it is actually on pin 2. I think that would rule that chip out, no?

u1 could be a JW5026

That does seem to match better. I got the full data sheet from here and pin 2 is on ground, pin 6 goes to L1 (an inductor), and pin 5 is connected to the red wire (via the diode at D2).

There's a cap across pin 1 and 6, just as the data sheet suggests, and pin 4 (which would be enable) is tied to pin 5 (Vin) through a 1meg resistor. And pin 3 (FB) goes to a resistor divider connected to the coil at L1.

So the pinout seems to match, if I interpreted everything correctly. What worries me a little is that the printing on the component doesn't seem to match any pictures of JW5026s that I found.

Are there any other measurements or checks I could do to confirm this is the correct part?

i dont see how shorting the switched 24v to ground or the sleep-input could have done that!

I'm a bit baffled myself. Then again, I'm easy to baffle.

[R_J]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

Then it is unlikely to be the R5325N005B if the pinout does not match

[stj]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

I'm a bit baffled myself. Then again, I'm easy to baffle.

i thought only doctors where baffled!

[redwire]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

I did a schematic for Quicko Ver. 3.3 T12 controller, I'll have to dig for it another guy was helping.

This V3.3 T12 controller board uses buck-converter U1 to drop 24VDC power down to 4.8V, which then goes to 3.3V linear regulator U5. A 1117-3.3 alone cannot take more than 15V input and gets very hot at that. Using just a buck converter works but is a bit noisy for the thermocouple amplifier.

U1 is JW5026 SOT23-6 SMT marking "JWBHJ" pin 3 resistors 2kΩ (R7 30B), 10kΩ (R5 01C) to L1 to give 4.8VDC output.
U5 is unknown SOT-89 linear regulator - sanded the numbers off. Note LD1117AG-33-AB3 some have reverse pinout and HT7533... I can't tell what pinout is needed on OP's board.

There is a danger the 3.3V rail went too high and blew the MCU or OLED. I would remove U5 and power the board up with 3.3V power only, and see if it works. If the MCU gets hot, well it's dead then.

[R_J]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

Here is a picture of the board with the numbers visible

[MyBrainIsAStrainer]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

Thanks again to all who replied.

Thanks to your input, I managed to get a little further. So, first of all: The MCU and OLED seem to be Ok. If I apply 3.3V at what would have been the output of the LD1117AG, the screen comes on and flashes "Error" at me. The broken LD1117 also failed open, not short.

Next I figured: Ok, it doesn't look like the 5V from the buck converter are needed anywhere else. They're really just an intermediate step in the creation of the 3.3V for the rest of the circuit. And I have one of those cheap LM2596 step-down converter modules. I could set it to create 3.3V from the 24V supply and botch it in to see if I can revive the station without any parts (at least as a test).

So I connected it in place of the broken LD1117. This time, powering everything with 24V via the supply cables. Same result as above: The screen comes on and flashes "Error". And yes, the soldering handle was connected and had a tip inside.

My next guess was: Well, maybe the 5V are needed somewhere else and I just can't see it. So I set the module to deliver 5V and connected it in place of the JW5026. I didn't have any LD1117AG but I had some AMS1117. Wrong footprint, but I just botched it in with some wires. Good enough for testing, at least.

Power everything up, same result: Screen comes on, flashes error.

I have 3 hypotheses:

1. The MCU somehow monitors the switching regulator at U1 and goes into error mode when it's not present/working.
2. There is another unknown fault in the board.
3. There is a fault in the handle.

Since option 3 seems the most likely to me, I opened it up and had a look. Does anybody know what that orange glass thingamabob is? It kinda looks like a diode, but has no polarity indicator. Maybe a TVS diode?

With the handle not connected to anything (and no tip inside), I read 10K resistance across it and a 2.7V drop in diode mode (both ways).

If it used to be some form of diode and got shorted to the heater voltage, it could've gone bad, right?

Any suggestions?

[stj]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

the handle contains a temperature sensor that looks like a diode,
a tilt/rattle switch, and the element
to get it to work you probably only need the element and it only uses 2 wires.
plug your tip in and then meter it from the plug at the other end of the wires
the resistance should be about 7ohms
and then make sure none of the wires are shorted to each other.
specially make sure the element wires arent shorted to ground

[MyBrainIsAStrainer]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

Wonderful! That did the trick.

The issue was: The metal contact which got bent in the original incident ended up a little bit... crinkled when I tried to bend it back into shape. That shortened it just enough so that it no longer made any contact with the tip, even when it was fully pushed it.

I attached a sketch to illustrate.

I tried to straighten the contact as much as possible, and now it works! I can even remove the AMS1117. The 5V really were not needed anywhere else. I tuned the LM2596 back to 3.3V and wired it up to replace the LD1117AG at U5, with the JW5026 at U1 completely removed. And it works.

Final question (hopefully): Is there any reason why I shouldn't just leave it like that? I assume the manufacturer had a reason for cascading a buck converter with a linear regulator. Maybe better stability? Or protection? I mean, this time the regulator blew up. Without one, if the new buck converter fails, will the MCU get roasted?

I think I should also order a new handle, just to be sure. I'm not sure I trust that metal contact in the long run. Material fatigue and all that.

[stj]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

it could be a noise thing, i'd atleast put something across the 3.3v like a polyester cap - maybe between .1uf and .47uf
whatever is in the spares box

i think the contact block can be found on aliexpress without the rest of the handle.

[redwire]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

Careful- the socket does short when swapping tips, and I add Kapton tape around it because a metal tube handle can also short it out.

It's good news the 2 vreg's shorting did not blow up the 3.3V rail.
T12 clone controllers, the chinese struggled with the power supply. Early ones used a linear regulator from 24V to 3.3V and they overheated. Then they went "expensive" with a buck regulator. Problem is they cheapen these so much, the capacitors are minimum size and then there is noise on the 3.3V rail affecting the thermocouple amplifier, and any drama with power surges can cause failures. Other models use a 100uF cap for the buck input.
OP if you shorted the 24V power, it might have overshot when recovering past 24V and first blew the mystery IC "W539" which I can find no data for.

I have most of the schematic finished but can't follow all traces. Would have to beep out a few I/O pins to confirm, if you are able to do that.
There is no crystal? I see they finally got rid of the battery and real-time clock. The CE1AH is a mystery EEPROM.
The diodes "T4" are 1N4148? ick that's seems weak for D2 buck input, I wonder if it shorted. Not sure what D1 is doing.

[MyBrainIsAStrainer]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

it could be a noise thing, i'd atleast put something across the 3.3v like a polyester cap - maybe between .1uf and .47uf
whatever is in the spares box

Good idea. The step-down module already has a beefy electrolytic on its output, but another... rummages through parts bin... 586nF won't hurt anyone.

the mystery IC "W539" which I can find no data for

As suggested before, it seems to be a JW5026. Or something very similar. The pinout and surrounding components match.

Not sure what D1 is doing.

It seems to go from the switching output of the JW5026 (W539) to ground. I'm going out on a limb here and speculate that it could be there to increase efficiency of the buck converter. When the switch is off and magnetic field in the coil collapses and its polarity reverses, the diode is forward biased and the current has a return path to the inductor. That way, the output capacitor is topped up on both phases of the switching cycle.

But I'm a moron, so I could be completely wrong here.

[redwire]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

Hey you want to help finalize the schematic? Here is a DRAFT so far. I can't see the traces to the MCU for TIP_TEMP, encoder, beeper etc. If you beep them out with a multimeter that would help. I didn't put the right EEPROM in yet, or D1.
The JW5026 has more parts (mosfet rectifier) and I think is much better than the "W539" which is a little different and seems to blow up a lot. But component shortages made the JW out of stock and all sorts of weird redesigns happened.
I think your LM2596 board will work fine, it has big capacitors so not as much noise as the stock setup. Another guy powered off XL boost-converter board to make a portable station off 12V 7Ah gel-cell.

[MyBrainIsAStrainer]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

I think D1 goes in like this (green).

I have continuity from the negative of the beeper to PA3, PA4, and PA5. The positive just goes to the 3.3V rail, as far as I can tell.

Encoder, when viewed from behind, starting in the bottom left corner going counter-clockwise: Pin 1 goes to PB3, pin 2 is ground, pin 3 goes to PB4, pin 4 to PA15, and pin 5 is ground again.

And pin 1 of U3 (TIP_TEMP) goes to PA2.

Disclaimer: I vouch for nothing except my own incompetence.

[redwire]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

That's great, last questions:

Resistor pack R10 pin 3, 4 not used? Pin 1 is bottom left
Resistor pack R9 pin 4, 5 not used? Pin 1,2,3 go to the encoder. Pin 1 is bottom left I am using as a ref.
OK where does MCU pin 11 PA1 go? Seems to go to R10 pin2

U2 EEPROM pin 1 SCL goes to MCU pin 42 or 43?
U2 EEPROM pin 3 SDA goes to MCU pin 42 or 43 or 11?
Still not sure where MCU pin 2, 43 go then as we have two I2C I/O but three traces.

[MyBrainIsAStrainer]

Re: Quicko T12-955 Repair (Board Rev 3.3): Help identifying components needed

Resistor pack R10 pin 3, 4 not used? Pin 1 is bottom left

If they go anywhere, I can't find it. However, I have secured my botch wires with some hot-melt glue, so I can't get to every contact on the board anymore.

Resistor pack R9 pin 4, 5 not used? Pin 1,2,3 go to the encoder. Pin 1 is bottom left I am using as a ref.

Pin 4 doesn't seem to go anywhere. Pin 5 goes to the 3.3V rail.

OK where does MCU pin 11 PA1 go? Seems to go to R10 pin2

That it does.

U2 EEPROM pin 1 SCL goes to MCU pin 42 or 43?

If we rely on the dot on the silk screen to identify pin 1, then it goes to PA0-WKUP (pin 10), and nowhere else, as far as I can tell.

U2 EEPROM pin 3 SDA goes to MCU pin 42 or 43 or 11?

That one connects to PA1 (pin 11).

Still not sure where MCU pin 2, 43 go then as we have two I2C I/O but three traces.

Pin 2 seems NC to me.

Pin 43 goes off to the vertical header above the beeper. I think it might be part of a programming header or future extension. If you look at the attached photo and the order of the through-hole pads therein, then:

Hole 1 connects to pin 2 and 5 of the MCU (or ground, whichever).
Hole 2 goes to pin 42 (PB6).
Hole 3 goes to pin 43 (PB7).
Hole 4 goes to ground again.
Hole 5 goes to pin 38 (PA15).
Hole 6 goes to pin 39 (PB3).
Hole 7 goes to pin 40 (PB4).