How to get rid of fluctuating voltage on soldering tip (T12 clone station)?

[Haggis McHaggis]

I have 2 if the T12 soldering stations but there are powered by 230 to 24v internal SMPS which have a proper grounding connection and that us the only really effective way to remove the risks associated with sensetive parts. I have replaced many mosfets with zero losses using this system. If you really must have a portable soldering solution then maybe a battery operated or gas powered system is the option that you should explore?

I think/hope my controller board is the same they use for the build in psu versions. It looks like they simply didn't connect earth (pcb label 'E') to anything other than the pcb and the tip. In other words the DC in connector on the board has 3 pins and the middle ('E') pin has the green cable missing.
A portable station is not what i'm after.

So if its not a portable version, you could perhaps sell the one you have on Ebay or something and buy a mains powered system with the built in psu? where the PE connection is taken right the way through to the iron tip?

The idea was to use an old psu i already had laying around and in addition hoping for a better quality psu this way.

[Specmaster]

I have 2 if the T12 soldering stations but there are powered by 230 to 24v internal SMPS which have a proper grounding connection and that us the only really effective way to remove the risks associated with sensetive parts. I have replaced many mosfets with zero losses using this system. If you really must have a portable soldering solution then maybe a battery operated or gas powered system is the option that you should explore?

I think/hope my controller board is the same they use for the build in psu versions. It looks like they simply didn't connect earth (pcb label 'E') to anything other than the pcb and the tip. In other words the DC in connector on the board has 3 pins and the middle ('E') pin has the green cable missing.
A portable station is not what i'm after.

So if its not a portable version, you could perhaps sell the one you have on Ebay or something and buy a mains powered system with the built in psu? where the PE connection is taken right the way through to the iron tip?

The idea was to use an old psu i already had laying around and in addition hoping for a better quality psu this way.

I don't see any downside to using the supplied PSU, I ordered from AliExpress Quick Heating T12 soldering station electronic welding iron 2018 New version STC T12 OLED Digital Soldering Iron T12-952 QUICKO which is the larger case, a 24v 108w PSU, handle and and 5 tips with the standard controller all included and is currently 39.40 Euros. I did however improve on the earthing of the case itself to ensure that every part of the enclosure was grounded. I have had these now since Jan 2018 and very happy with them and fitted MOSFETs with them and never had a single problem with them.

On the the other hand, you and and bd139 both seem to have problems with the portable version which I suspect would be perfectly fine if it's fed with pure 24v from batteries.

Personally I'd be inclined to sell the one you have and purchase a complete new system from AliEx and sell what you have.

[bd139]

Agree with buying one with the PSU inside it. Possibly with a Metcal badge on it 

To work around it when I was using it, I plugged the negative into the earth on my bench PSU. Have to watch out you don't have an earth fault though otherwise things get interesting pretty quick.

[Haggis McHaggis]

Hmm, but what is difference between adding an earth jack versus using one with build in psu? Is this not the same technically?

One advantage of external psu would be more space on the workbench.

[bd139]

It works out about the same at the end of the day electrically. Based on the fact you already have it, grounding it is best approach.

The tiny case on the low voltage one tends to get dragged around everywhere though so there's an advantage there.

[Haggis McHaggis]

I have 2 if the T12 soldering stations but there are powered by 230 to 24v internal SMPS which have a proper grounding connection and that us the only really effective way to remove the risks associated with sensetive parts. I have replaced many mosfets with zero losses using this system. If you really must have a portable soldering solution then maybe a battery operated or gas powered system is the option that you should explore?

Is GND/DC- and earth bridged in your stations? I ask because in my station GND/DC- is connected to the case. I assume if i had a separate earth that would be connected to the case (and E pin on the board) instead of GND/DC-. Do i get that right?

[Haggis McHaggis]

Found another T12 diy station with instructions. The first photo shows how to connect earth to DC-, leaving the E pin unconnected. I wonder why its not connected to the E pin.

https://www.aliexpress.com/store/product/Electric-Unit-LED-Digital-Soldering-Iron-Station-Temperature-Controller-DIY-Kits-use-for-HAKKO-T12-Handle/2954088_32836960037.html?spm=a2g1y.12024536.productList_5404174.pic_0

[Specmaster]

Found another T12 diy station with instructions. The first photo shows how to connect earth to DC-, leaving the E pin unconnected. I wonder why its not connected to the E pin.

https://www.aliexpress.com/store/product/Electric-Unit-LED-Digital-Soldering-Iron-Station-Temperature-Controller-DIY-Kits-use-for-HAKKO-T12-Handle/2954088_32836960037.html?spm=a2g1y.12024536.productList_5404174.pic_0

Please do not connect Earth to DC- it is wrong for the Quicko system, I'll post some photos shortly for you of my Quicko T12-952 system and there is zero connection between DC - or + and Earth. The entire system has its own integral earth connection which grounds all of the metal enclosure and the iron tip which are all bonded together, using the Quicko supplied recommended power supply (24V 108W) and as already stated works perfectly and I have soldered many sensitive parts with it and 100% success rate.

[Haggis McHaggis]

Thanks. It may be the best to copy that for my station.

A few days ago i contacted the quicko store service and asked for manual and schematics, but didn't get anything. 

[Specmaster]

As promised here are the photos of my system and I have identical systems apart from of them is built into a very slightly longer case.

It uses a 4 pin plug and socket for the connection of the iron handle and please note that I no longer use the standard handle as supplied with the system when purchased, although it does still work ok with it, I now use the T12-9501handle system as it provides better physical control over the tip, the standard handle has more of the tip exposed, otherwise they are same electrically.

I have confirmed that there is zero electrical connection between the DC supply and the Earth/GND connections using my DMM on continuity setting. As will see, I have provided a GND connection stud at the back of the enclosure to ensure that the enclosure is safely Earthed as the power supply is held in 2 rails on the bottom section and this does not provide a very good GND connection to the enclosure, hence my modification. This has been reported to Quicko so that may no longer be the case as I have had mine for 16 months now so they may have modified the earthing.

[Haggis McHaggis]

Thank you for the photos.

T12-9501 handle here too.

I think i need to isolate my DC jack from the case first. Maybe using a plastic DC jack. Then use a M3 or M4 screw or a banana jack as Earth terminal connected to the case. I assume i then have to connect this Earth to the E pin on the board. Is this correct? Do i still need that 1K resistor (between DC+ DC-) in this scenario or can i remove it?

[Specmaster]

I would think that you could do away with it if your going for a full on earthing.

[Ian.M]

Did they fit the 1K resistor just to be funny and mess with you?  Probably not!   It provides a discharge path for the PSU's secondary side reservoir caps. Without it, the statiuon may not reboot cleanly if you turn it off then back on again at the wall without waiting several minutes in between.

[Specmaster]

In this case, the unit does not come with a PSU, you have to provide that or use an existing one and as such surely, if the PSU needed that 1K resistor, it would have been built into the PSU brick?

[Ian.M]

I'm not suggesting the 1K is a minimal load for the PSU (though if they found out their own PSU needed that, I can see it could be cheaper to fit it in the station rather than reworking a large batch of sealed PSUs), I'm suggesting it *MAY* there to make sure the input voltage goes all the way down to zero if its switched off at the wall for a  second or so so the MCU in the station conroller gets a clean reset.  Some types of MCU are known to have problems with POR if the supply voltage doesn't start from zero at switchon.  If they've run into that issue, a resistor to guarantee residual charge is drained  while off would be a cheap & easy fix

[Specmaster]

Well, the PSU is not of their making, it is in fact one that the OP already had. Quicko don't make an external PSU for their solder stations, they offer them with internal ones, of which I have 2 of them, or like the one the OP has which uses a smaller enclosure and is fitted a 2.1 mm DC power jack so the user can use an existing laptop PSU or use 24v batteries, in which case the resistor is not required for a minimum load etc.

[Haggis McHaggis]

I got a reply from Quicko that said i can wire it according to their diy kit wiring diagram (posted earlier in this thread or Specmaster's built in psu version, it's the same), BUT i'd need a power supply like theirs.

The question is whether my psu is like theirs or not? On my psu it looks like DC- is somehow coupled to PE through a 1M resistor. (i posted some measurements earlier) Has their psu a completely isolated PE with absolutely no connection to DC? @Specmaster Can you somehow determine if your built in psu has a coupling or isolation for PE?

Edit: @Specmaster
In your post with the photos of your station you wrote about continuity testing PE. Did you measure resistance too?

[Specmaster]

Yes I did measure resistance too and there is NO connection between the DC output of the built in PSU and the Earth / Ground and neither is their a resistor between the DC and Ground either. Its 240VAC into the PSU via switch and a fuse, DC out to the iron controller and then DC via the iron controller to the iron tip. The main incoming Earth is directly connected to the PSU earth rails along the sides of the PCB, to enclosure and also to the Iron tip casing.

[Haggis McHaggis]

Thanks Specmaster.

So my psu is not like theirs/yours. Should i then simply short DC- with the tip/E pin on the board? That way the tip would be connected to earth via 1M. But i'm not sure the 1M resistance between PE and DC is some kind of error in measurement.

[Specmaster]

Thanks Specmaster.

So my psu is not like theirs/yours. Should i then simply short DC- with the tip/E pin on the board? That way the tip would be connected to earth via 1M. But i'm not sure the 1M resistance between PE and DC is some kind of error in measurement.

Let me get this straight, the photo of the PSU you posted, is that the one you're using? If so, is it one that you purchased specifically to power your soldering iron, or was one you already for a laptop? I say laptop because that is what Lenovo do, they make laptops and the PSU's to go with them.

Could you dismantle your solder station and take photos of the controller and post them here for me?

[Haggis McHaggis]

Thanks Specmaster.

So my psu is not like theirs/yours. Should i then simply short DC- with the tip/E pin on the board? That way the tip would be connected to earth via 1M. But i'm not sure the 1M resistance between PE and DC is some kind of error in measurement.

Let me get this straight, the photo of the PSU you posted, is that the one you're using? If so, is it one that you purchased specifically to power your soldering iron, or was one you already for a laptop? I say laptop because that is what Lenovo do, they make laptops and the PSU's to go with them.

Could you dismantle your solder station and take photos of the controller and post them here for me?

Yes, the Lenovo psu on the photo is exactly what i use to power the soldering station. I didn't purchase it specifically, i had it laying around here. It is made for Lenovo laptops.

I already thought about disassmbling the station to have a better view on the board, but they glued the board connectors to the power switch on the backpanel. So not as easy to do as i'd like.

Meanwhile i made a test with a 1K resistor between DC- and the tip and measured the DC voltage over this resistor. The voltage drops to about 0.02 with the resistor (was fluctuating 0.5-3V, sometimes up to 10V before). Does that mean i can safely short DC- and tip and be done? If yes, i thought about putting a switch into the back panel to make grounding the tip switchable.

[Specmaster]

If its a genuine Quicko station then the front and back plates are held in place by 4 cross point screws each, removing these screws will allow the the end plates to laid flat so you photograph them still connected. I'm keen to see if the actual controller is the same or not as mine. I understand that there are other versions of controller on sale and that some of them may not be fully compatible.

[Haggis McHaggis]

I've attached some photos.

The board is not the same as yours, but has the same connectors. I think it is pin compatible.

ps ordered from quicko store @AliX

[Specmaster]

So your 1K resistor is located there on the front panel rather than on the DC jack at the back? I think that I'd personally be tempted to try it with the resistor left in circuit and run a earth lead directly to the metal case or ever that 1K resistor is connected to and do a test of that way and see if it has any effect on the the way that the iron behaves and also measure the leakage to the tip.

[Haggis McHaggis]

I'm a little confused. Do you mean the 1K resistor you can see on my photos above? That resistor was built in by Quicko and is connected between DC- and DC+.

The other 1K resistor, not seen on the photos, i used to test shorting DC- and the tip (aka earth), which seemed successfully eliminate the actual 'voltage on tip' issue.

I hope didn't confuse all of this even more.