Aixun T3A overshooting?

[tony359]

Hi all,

I've just purchased an Aixun T3A T245 soldering station and I am pretty happy with it, coming from a Hakko knockoff.

However, I purchased a genuine JBC tip and the temp massively overshoots with it. I can see a similar behaviour with the Aixun tips but not so horrible.

With the JBC tip on the thermometer I see the temp more or less stable but slowly dropping. At some point there is a 100% power spike and the registered temp goes +40C from where it was - obviously the display doesn't show anything!

Is this "expected"? 40C seems quite a lot.

See a video of what's happening here: https://youtu.be/z6oj99W5PH0

I am just holding the tip on the thermometer, no wet sponges or anything.

[stj]

Re: Aixun T3A overshooting?

maybe software - is it the lastest version?
https://aixun-updates.github.io/

[tony359]

Re: Aixun T3A overshooting?

it is, you can see 1.34 on the display.

It does look like a software issue to me. I've reported it to Aixun, also mentioning I am reviewing it, it might get some traction

The funny thing is that a couple of versions before it said "fixed overshoot on 245"
Maybe I should try downgrading!

[tony359]

Re: Aixun T3A overshooting?

Aixun replied to my enquiry saying it's intentional (of course!).

It might make sense though: they say it's designed to give the tip a little boost when the solder is being melt, to prevent the tip from dropping the temperature too much.

I admit that when measuring on a thermometer there is no mass, hence the test is kind of "unfair". On a proper solder joint I'd imagine the overshoot is not as bad.

Still, with the smaller knife tip that does not happen so... uhm...

[stj]

Re: Aixun T3A overshooting?

to be fair then, it's probably the tip mass causing a delay between the sensor and heating element thats hard to predict in software.

[tony359]

Re: Aixun T3A overshooting?

well... you can see the temperature is creeping down for no apparent reason. I see what you mean and I don't disagree but I feel there is some improvement possible in keeping a more stable temperature when the tip is not doing anything.

The software should push a tiny little more power in the tip to avoid the temp going below the threshold which likely triggers the "temp has lowered, they must be soldering, let's pump 200W to the tip to compensate".

Does the station know what type of tip is being connected? I remember watching some reviews (not sure about what station) where it was being mentioned that the reason why the full 100% power was not being sent to a specific tip was because it was too small to take that amount of power.

Indeed a "high thermal efficiency" tip would require more power than a very small, tiny precision soldering one.

[stj]

Re: Aixun T3A overshooting?

no, it doesnt know what cartridge it is.
in theory if you had a menu to tell it the cartridge model it could compensate by having a lookup table.
one of the cheaper units - maybe quicko or ksger has a tip menu that lets you set different offsets for the temp, so it's possible

there is a very expensive station that does have an eeprom in the cartridge but thats going to be stupid money.
i think it may be hakko or weller but not sure - it's not been cloned anyway.

[tony359]

Re: Aixun T3A overshooting?

ah gotcha. Then I guess it's kind of understandable even though I still don't understand why the unit is letting the tip cool down to a point where it deserves a 170W boost
The tip does not cool down instantly so in theory the algorithm has plenty of time to realise it needs to push the power a tad more. Uhm...

Someone on my video recommended to downgrade to 1.33

[tony359]

Re: Aixun T3A overshooting?

Turned out the issue was already mentioned on EEVBlog forum and indeed downgrading to 1.33 fixed it.

Too bad for Axiun who replied with Marketing BS to my query. But hey...

[stj]

Re: Aixun T3A overshooting?

in regard to your comment about 170w boost,
soldering stations use PWM driven mosfets.
it's either 170w or nothing - it's the duration that counts

there is a project to reverse engineer the T3A, they have extracted the firmware and i think created a schematic.
maybe they will eventually customise the firmware
https://github.com/c0d3z3r0/aixun_t3a_rev

[tony359]

Re: Aixun T3A overshooting?

Yes, of course it depends on the duty cycle. There is a power indication on the display, it goes up to 87% which of course it doesn't mean it's delivering constant 170W but the duty cycle is adjusted so it's 87% of the max power... you know what I mean

ahah, we reverse engineered the reverse engineered one

One thing I might have noticed with 1.33 is that the station is noisier? It's buzzing louder.

[stj]

Re: Aixun T3A overshooting?

i didnt know it buzzed?

[CapLeaker]

Re: Aixun T3A overshooting?

No buzzing in mine.

[tony359]

Re: Aixun T3A overshooting?

I read online that the new version buzzes more than the old one. Mine says "HW version 1" (or maybe 0?) so not sure. Interesting

However I have a much bigger problem.

I've used the T3A to do some soldering tonight and noticed the display would say "NO TOOL" every now and then. I thought it was my JBC tip so I swapped it for an Axiun. Same issue.

Then I realised it was not the tip. EVERY time I was touching some specific pins on the motherboard I was working on, the station does what you see on the video.

The MoBo is disconnected, been off for days, no battery.

How is that even possible please and, most importantly, what do I do now?
I am incredibly confused.

https://www.youtube.com/watch?v=o5JEp6sO9Jc

This is what the display says when it "flashes"

[CapLeaker]

Re: Aixun T3A overshooting?

Mine doesn’t do that. I even soldered big stuff with that iron that shouldn’t be done with one. I am not even sure what firmware or hardware mine is running, but it is about 10 months old now.

Looking at your video, it looks like it’s going crazy as soon the main unit ramps power up close to full tilt, losing juice. Weird. If you just got it and depending where you bought it, warranty it?

[tony359]

Re: Aixun T3A overshooting?

I don’t think it’s got to do with power, I’m barely touching some specific joints. I’ve done the ‘coin’ test with lots of solder and I can dip the tip in a wet sponge and it doesn’t happen.

Yes it’s brand new so o guess I’ll ask for a replacement, wish me luck.

Still, I can’t think of what could be sensing that is triggering that behaviour.

[tony359]

Re: Aixun T3A overshooting?

I have an update. It's ground.

When the PCB I am soldering is grounded, SOME solder joints will cause havoc.
AND, the handle is buzzing.

https://www.youtube.com/watch?v=8OXDOZTy7t0

[stj]

Re: Aixun T3A overshooting?

contact Aixun - it's gotta be a psu issue
my guess is the ceramic capacitor between the primary & seconday is missing or the unit is missing a ground connection between the mains earth input and the handle somewhere.

can you use your meter to check resistance between the iron tip and the earth pin on the back of the unit - earth on the iec connector i mean.
while your at it - check your power cable and your house socket

i'v had a few recent "incidents" with power cords with molded plugs on them!!!!
if you buy anything high wattage with a molded plug - check the plug isnt getting hot while it's running - specially fan heaters from Lidl!!

[tony359]

Re: Aixun T3A overshooting?

Shall do, I did check that the unit was earthed, I believe everything reads full continuity but the tip which is reading some resistance but not much? I'll double check.

Bear in mind that when I touch ground directly with the tip, it does not happen. It only happens when touching SOME solder joints on an earthed PCB.

I'm not sure about the PSU to be honest. The display would show "undervolt" or something like that, like it does for a brief moment when you power it off.

Someone on EEVBlog says this is normal - I can't accept a soldering iron which cannot be used on grounded equipment, would you agree?

[stj]

Re: Aixun T3A overshooting?

it makes no sense.
the tip resistance to mains earth should be almost zero

*unless* it's floating for safety - but i dont think they did that.
weller in the past used to connect the tip to mains earth through a parallel resistor and capacitor to limit current incase you accidentally worked on something live.

i modded my t12 the same way - sometimes i can get leds to glow while soldering them now!