Quecoo T12-955 Soldering Station tip and case grounding modifications - Page 1
Forum section: electronics / general

author: Basileus
author_rank: Regular Contributor
timestamp: January 10, 2022, 06:27:27 pm
content: Hi, i just received the generic T12 soldering station i ordered (Quecoo T12-955, listing here:https://it.aliexpress.com/item/1005001608493682.html) and noticed that the case isnt grounded (expected) and neither the tip is (unexpected). I looked into it and on the board the PSU connects to the uC PCB through a 2 pin connector even though the female on the board is 3 pin:and already has the earth ground connection straight from mains plug to the connector (pic borrowed from other thread):I then checked how the handle is put together:And found very weird that the outer jacket of the tip is shorted to ground and the NTC and mercury switches are attached to its connection as well. So I was thinking of fixing this, properly grounding the tip (and eventually later the chassis as well). I have a couple of questions:1. Is this wiring diagram of the handle modification correct?The new ground connection would be on pin 3 of the GX connector, which is currently shorted with a 0 ohm resistor. Here's a picture of the board (not my pic but visually checked they look to me the same):Earth connection coming from the connector would be soldered on through hole labelled "PE"2. What is the model of the 3 pin connector i need?3. My handle currently uses a mercury switch for the shake function, would it be fine to eventually replace it/ get a handle with a ball switch (since those seem to be more popular)?Thanks in advance

author: floobydust
author_rank: Super Contributor
timestamp: January 10, 2022, 07:07:24 pm
content: TBH the electrical safety standards require PE ground to be capable of handling the branch circuit current which is typically 15A. If the fuse is actually in the Line, then this can be less but in china they wrongly put the fuse in Neutral all the time.In other words, that skinny PE PCB trace is unsafe and just run an 18ga wire from the IEC ground to 24VDC(-). The controller boards often have a special PE ground pad if you look for that.You could jumper pin 2,3 on the DC connector but again, the trace is too skinny.I don't know why you are changing the handle wiring, the tip and heater and housing are bonded together inside at the thermocouple, so the shake switch wiring I would leave alone.

author: RayRay
author_rank: Frequent Contributor
timestamp: January 10, 2022, 07:10:51 pm
content: Quick fix on the picture attached. I'd recommend you use a 22AWG wire at minimum.Good luck.Edit: For safety reasons, it'd also be best you remove the board first (so the metal pieces scraped wouldn't go on it), or alternatively, at least go over the area with a brush afterwards

author: Basileus
author_rank: Regular Contributor
timestamp: January 10, 2022, 08:11:55 pm
content: QuoteIts wired correctly, but still, all plugs in Italy are not polarised so it doesnt really matter...QuoteIts right under Pin 3 of the GX connector. (see attachment)QuoteI subconsciously thought i might want to separate signal ground from earth ground, but if its fine to tie them together i can do it (actually i think thats what most other similar T12 stations do since there are a bunch who have continuity between iron tip and IEC earth but only have a 2 pin board interconnect). Is it?QuoteI dont understand this. The tip is insulated from the thermocouple and heater (which are wired in series) isnt it?

author: Basileus
author_rank: Regular Contributor
timestamp: January 10, 2022, 08:14:20 pm
content: Quote from: RayRay on January 10, 2022, 07:10:51 pmOh so its fine to keep earth and signal ground tied together?Soldering directly to the back plate of the casing? is it possible? My only other soldering iron is 40 watt.Thanks a lot!

author: DavidAlfa
author_rank: Super Contributor
timestamp: January 10, 2022, 08:45:21 pm
content: All the thing around the fuse in the live... meanwhile most european countries have reversible plugs without any marking to differentiate live and neutral

author: RayRay
author_rank: Frequent Contributor
timestamp: January 10, 2022, 09:05:21 pm
content: Quote from: Basileus on January 10, 2022, 08:14:20 pmYou're very welcome.As for your questions, earthing is technically connecting the metal case and/or externally used metal part of the equipment to the ground, which is what you'd be doing with my given instructions. Both the case & solder iron should be grounded afterwards. And yes, you could solder it directly just fine (provided you'd scrape off the paint from a small area of it first)

author: Basileus
author_rank: Regular Contributor
timestamp: January 10, 2022, 10:04:38 pm
content: Quote from: DavidAlfa on January 10, 2022, 08:45:21 pmI'm definitely soldering a 4 pin header on the SWD interface connections and giving your T12-955 a spin after a backup, david

author: Basileus
author_rank: Regular Contributor
timestamp: January 10, 2022, 10:10:11 pm
content: Quote from: RayRay on January 10, 2022, 09:05:21 pmI'm still wondering about signal ground. My original plan was to isolate the tip connection from the rest of the circuit, and attach attach it to PE through pin 3 on the GX connector. Currently both pin 3 and 4 are connected to circuit ground/signal ground/VDC negative. I was asking it its fine to keep everything connected together.

author: RayRay
author_rank: Frequent Contributor
timestamp: January 10, 2022, 10:38:05 pm
content: Mixing DC negative with ground is fine. Anyhow, I'd say you're overthinking it.

author: Basileus
author_rank: Regular Contributor
timestamp: January 10, 2022, 11:35:37 pm
content: Quote from: RayRay on January 10, 2022, 10:38:05 pmOh ok I guess, I'll definitely do it. Thanks a lot!

author: DavidAlfa
author_rank: Super Contributor
timestamp: January 11, 2022, 01:25:30 am
content: Quote from: Basileus on January 10, 2022, 10:04:38 pmGreat! There's already a backup for the 955 so don't get too scared

author: floobydust
author_rank: Super Contributor
timestamp: January 11, 2022, 02:30:19 am
content: Quote from: DavidAlfa on January 10, 2022, 08:45:21 pmHow does that work with a 3-pin IEC-entry? I think these stations end up having two fuses, one in the IEC entry and another on the PSU PC board.

author: DavidAlfa
author_rank: Super Contributor
timestamp: January 11, 2022, 04:51:23 am
content: Yes, the IEC connector can only be connected in one position, but the Schuko plug at the wall isn't polarized, same with the Europlug.

author: Mickk
author_rank: Newbie
timestamp: January 11, 2023, 06:48:19 pm
content: Hi,I can confirm that the brand new Quecoo T12-955 I have received today (11/01/2023) is still not grounded - neither the case, nor the soldering tip.Of course, the missing case grounding is not compliant with applicable CE/VDE regulations. Additionally, I believe that the potential between GND and soldering tip - in my case - of 195Vpp would be quite critical to ESD sensitive devices. So I decided to ground the case and the tip, too:- I soldered a cable to the GND pin of the IEC socket and screwed this cable to the housing with a soldering lug. The screw connections in the housing and the housing itself at these points are of course all bare and conductive, including the 5-pin socket to the soldering iron.- This is still not enough, because there is still no connection between DC negative (and soldering tip) and chassis ground. I solved this by soldering a connection under the header from the power supply board to the control board.I think this might help others with similar concerns.

author: bmac_2780
author_rank: Newbie
timestamp: January 14, 2023, 09:51:05 pm
content: Fitting a screw to rear panel and connecting that to the IEC Earth pin, as described by a couple of people here is a good start. But in my opinion not sufficient to ensure the whole enclosure is grounded, and certainly not sufficient to comply with any safety legislation. You are relying on the 8 screws (4 for front panel, 4 for rear) to provide electrical continuity to the other 3 panels forming the enclosure. On my T12-956 I used a countersink bit to lightly remove the black anodising from the countersunk holes on the front and rear panels. Then I used new M3x10 Csk zinc plated screws instead of the originals and screwed them in tightly. Finally I did a continuity test to each panel. Note anodised aluminium is an electrical insulator! It is important to remove that if you want to make a connection.A person with OCD might run a separate earth wire to each panel and connect each with a screw, star washer, ring terminal and nut onto an area scraped clear of anodising. I have seen that one some pro audio equipment that had anodised panels.

author: Mickk
author_rank: Newbie
timestamp: January 15, 2023, 12:46:52 am
content: Well, yes. As already mentioned:Quote

author: Piasecznik
author_rank: Newbie
timestamp: January 19, 2023, 12:39:56 am
content: Hi, just my 2 cents. I also removed short between PE and controller GND but did not modify handle yet. It turns out to somehow energize HV cap on power supply board and when it reaches around 30V it switches on for fraction of second and makes a beep. With power switch on back of the unit turned off! Imagine me trying to figure out what was source of those beeps.I have KSGER with black 2.05 power supply board and green V20 (MM32 based) controller board.