Quecoo T12-958 soldering station - INVER error?

[spleenharvester]

the resistor/link really depends on your work and if your supervised by a rule following scumbag.
legally it's supposed to be earthed, the resistor may count but i'm not sure.
if it is then you cant work on live circuits or big charged capacitors though.
i use a resistor on mine but it's bigger than 100k from memory.

getting back to the fault, interesting - can you try with the dc supply and meter the voltage at the pcb as it heats up?
maybe the voltage is dropping because a cable or other part is under-rated

I've done some more playing around and can confirm reproduceably it only happens on DC, and only happens once the iron starts from cold. If the iron is already >100*C, it doesn't cause the error. So I think that reasonably rules out the handle.

This is really perplexing me - the DC voltage on my current power supply (an Einhell 4Ah tool battery) is stable at +20.8V during warm-up and when the error occurs. The voltage on AC is +25.2V. According to the AliExpress listing the acceptable range is 19V to 24V so this difference can't be causing my problem surely? And this battery can output something like 25A CDR so I can't imagine current is a problem.

Quecoo replied saying 'there is a shrapnel [sic] that needs tightening with pliers in the handle', whatever that means. But they seem to be wrong as the handle is fine on AC.

(As an aside - some more poking around, I've found the green earth wire Quecoo added between the PSU and the controller board doesn't actually connect to anything lol it's just a lone pad on the controller board side)

[stj]

the resistor/link really depends on your work and if your supervised by a rule following scumbag.
legally it's supposed to be earthed, the resistor may count but i'm not sure.
if it is then you cant work on live circuits or big charged capacitors though.
i use a resistor on mine but it's bigger than 100k from memory.

getting back to the fault, interesting - can you try with the dc supply and meter the voltage at the pcb as it heats up?
maybe the voltage is dropping because a cable or other part is under-rated

[spleenharvester]

do you have any more cartridges?
also, on some early irons people had to open the handle and bend the spring contacts
you can inspect the soldering on it too

Yip, same thing happens with a new cartridge.

Soldering looks good at both the connector and in the handle, doesn't look like anything is shorting. Contacts within handle have been bent and it still does it. I don't think this one is a connection issue as if you keep the iron in exactly the same place without touching it the problem is reproduceable.

It seems to be something about that 70-80*C point that trips the error. Every time it heats up to that point it triggers [INVER]. If you restart the station while the handle is above 80*C it will heat up no problem. If you restart the station and let the handle cool to <80*C first it triggers the error. Very odd. Would help if I knew what the heck that error means. I wonder if the motion sensor in the handle has failed or something?

EDIT - OK a bit more info - the error is actually [INVERT] and it only seems to happen on DC24V, it's fine on AC. Happens with multiple DC24V supplies that support >4A. I've been pouring through the custom T12 firmware project files and can't find any reference to this error.

Side Q - should I have put a 100K resistor from tip to earth? I bridged the tip earth pin to the mains earth pin as it was unearthed but I've just seen a schematic that seems to put 100K between?

[stj]

do you have any more cartridges?
also, on some early irons people had to open the handle and bend the spring contacts
you can inspect the soldering on it too

[spleenharvester]

I bought a T12-958 recently with an M8 handle and until now it has worked very well. The tip wasn't earthed but that was easily resolved.

Now, whenever it is switched on, it heats up to about 70*C then shows an [INVER] error on the screen and stops. In order to fix it I have to either unplug and re-plug the handle, or unplug and re-insert the tip from the handle. While doing that it changes to [ERROR], then it finishes heating up and works perfectly. Until it's turned off, after which it will show [INVER] again next time it is turned on.

Any idea what the problem is?