1. See the video annotation @6:44 where I had confirmed the USB-A socket (shell) is connected directly right through to the tips, hence I didn't bother to show the final result on the multimeter. th-cam.com/video/se6-jGZsHS0/w-d-xo.html 2. I have been in contact with Secure and they have promised to do something about this issue. 3. Why the Micsig?....Just a precaution as the Rigol scope is USB power also and although it has an earthed PSU it exhibits about 0.8Vac on the BNC shell relative to mains earth. I wanted full isolation to rule out any ground loops etc.
Hi Ian: A few comments if I may 01:10 If you live in the EU for example (as far more people do than live in the UK) then we only have two pin mains plugs, that are also reversable : So the grounding issue you raise is just a local one 02:10 We tried to reproduce this on the live stream a week ago and couldn't. Do you think it is due to the power supply you are using rather than the HT140 as we didn't use that one. Yes I know it is the supplied PSU but it can't drive the tweezers properly so we used a third party 140W supply. We also tried using a USB power bank with the HT140 and couldn't replicate this problem with that either, which is unsurprising as the power bank is not connected to the mains. Try using a USB power bank yourself and see what you find then let us all know if your results agree with ours. Also if you take a multimeter and measure the resistance between the two tips you will find that they are connected together (zero ohms) so you can't possibly have 300V between them 😉 05:39 - only if the device you are repairing is grounded! As general point, an electronics workbench should not be earthed it should be connected to an isolation transformer. This is because it is much safer. Use a grounded antistatic mat of course but that has a very high resistance (megaohms) to ground. So if your DUT, isn't grounded or plugged into the mains while you are soldiering (and why possibly would it be??) and the two tips of HT140 are connected to each other please elaborate how this can damage anything? This is not a criticism of your opinion, I'm up for a good discussion about it. Be nice to hear from you.
I am in the UK (Scotland actually, the better end!). I bought the HT-140 kit from Sequre and they supplied the PSU. So far, it works fine irrespective if grounded or not. Yet to put it under heavy load but so far so good. Here's my opinion: This is not an issue of whether soldering iron tips should be floating or not, it's an issue of whether the workbench should have actual real leakage currents and capacitive coupled large voltages should be left to occur. When you apply the iron tips to a PCB then one or both of them will come into contact with the PCB and depending on the potential the circuit is at and due to the leakage current / capacitive coupling a large potential between them MAY occur. Saying that, if it is a floating circuit, i.e. not plugged in anywhere) then you are at the mercy of any floating circuits and the voltage potentials across the entire system may or may not do. Example: I just grabbed a PCB and put it on the workbench (grounded EE bench mat so ESD not an issue). It's not plugged in anywhere, totally floating, and I just measured the voltage between the iron tips and an IC component leg on the PCB. - Without blue cable earth fitted = 36VACrms - With blue cable earth fitted = 2VACrms The air in an around the workshop is having an effect of naturalizing/pulling floating voltages on circuits. So, it's better to have the iron tips earthed IMHO. Better to take the issue out of the equation totally IMHO. If the tips were floating WITHOUT the leakage current / capacitive coupling problem then it would be much better......but they are not. I haven't opened up the Sequre PSU yet, but suspect its a Y capacitor issue that's injecting primary --> secondary and finding its way to the tips. The use of an isolation transformer is not mandatory on any EE workbench (I have one), just when they need arises I think most EE's will look at it. I have been in touch with Sequre and they are looking seriously at providing a cable so users can optionally do what I did. PS. I have two BM786 DMM's........the first one I tried during the making of the video turns out of found it had a blown 400mA fuse on the current circuit. One wonders why! Ian.
@@IanScottJohnston Hi Ian Yeah I figured you are from the better end of the UK 🙂. I'm originally from one of the less pleasant parts, Stoke-on-Trent, but in July 2016 I figured it was quite likely to get a lot worse and moved to the south of Gran Canaria. Anyway, electronics, so for any current to flow anywhere between two potentials there has to be a current path. If the PCB you are working on is not grounded then no current can flow from the soldering iron tip into it, as at the instance the tip touched the PCB both become the same potential. Of course if there is some sort of capacitive coupling between the PCB you are working on and ground, and there is also an instantaneous current path from your soldering iron via the PCB to ground but only while that capacitance charges up I have the same PSU with the HT140 as it was supplied with the review sample. I tried that one and also a 28V 5A PD3.1 supply and there is a notable improvement with the HT140 performance so I would honestly recommend you get a PSU rated at 28V 5A as it's well worth the money. I got a fairly cheap PD 3.1 supply from AliExpress and that does power the HT140 properly... with a few quirks (I'll publish a video on that soon) I would suggest that anyone using a USB soldering iron of any sort, who is worried about earth leakage, just run it from a power bank and the problem is eliminated. Re Isolation Transformer, it's not mandatory but it is a *very good idea* and has surely has saved me from dangerous electrical shocks on more than one occassion. I'm sure you are totally correct that the floating potential is coming from a High Voltage (Y) capacitor in the PSU connected between the primary and secondary winding. The severity of this problem will vary from one PSU to another which may be why we couldn't replicate this issue. On another live stream we actually removed the Y capacitor from a small 'wall wart' SMPS to see what would happen. It continued to work just fine. Yeah I know it may cause high frequency noise on the mains wiring but we didn't notice any detrimental effect from doing so and doubt you would see any real world consequences from just removing it.
This issue is a potential problem with any USB powered soldering iron. Anyone using a USB soldering iron should take note. The voltage and energy available in that leakage current could easily damage more sensitive devices such as RF FETs, I don't think I have ever seen a USB wall wart with an earth ground connection. I wonder how many even connect the shield connection internally. Thank you for bringing attention to this issue and offering a low cost solution.
I like to include some resistance in a soldering iron ground - just in case. With real transformers 1 Meg works. But you have a switcher so there will be current through the dreaded Y caps. 1 meg will leave a lot of volts on the tips, so maybe 1k.
4:12 It's interesting that the Vpp measurement is much more than the "normal" 2*Sqrt(2) * VRMS. Presumably this is because the waveform is quite non-sinusoidal. The ratio of these measurements does note even have the same ratio for unloaded versus loaded with 100k.
I would have liked to see a verification step with the differential probe connected between the mains earth wire and the iron tips to see if that 100V AC on the tips has been pulled to ground. We don't actually know if the soldering tweezer tips are connected through to the USB shielding nor if the power supply is properly connecting the shields across the 2 USB ports
See the video annotation @6:44 where I had confirmed the USB-A socket (shell) is connected directly right through to the tips, hence I didn't bother to show the final result on the multimeter. th-cam.com/video/se6-jGZsHS0/w-d-xo.html
@@IanScottJohnston Oh I'm sorry! I didn't notice that annotation! I was looking at your fingers touching the earth wire and not paying full attention to see the annotations
Even with that relatively high source impedance I can imagine even some low voltage capacitors would not be really happy if they caught the full peak voltage, never mind silicon devices.
Humm interesting, I’m in the US and our neutral is bonded to ground in our main panel I’m wondering if I would see the same thing or that bond would be enough? I may need to check this out!
Hi Ian, does the temperature control still works correctly ? I have seen on a soldering station review that wasn't grounded, that the temperature went above 440° C while the set temperature was only 360° C. This was caused when soldering on a grounded circuit. The video where this can be seen : th-cam.com/video/B7jLpHgR7fI/w-d-xo.html
I like the weller soldering stations where the tip connection is via a jack socket. So you can short the tip to ring in the plug and once plugged in ground the tip, or it allows you to fit any value resistor you want. I like a 10k resistor nice pull down to earth for leakage but will not pull too much current if you decide to work on with some voltage still present after turning off. Looks like I might have to see if santa has any money left over, as the covid-19 like present he gave could not have been too expensive 😂😢. Went down on the 25th and the shi* is still working its way out 😢
Another option is to leave the USB cable whole and create a USB-Banana adapter with a resistor of choice. However, doing this type of workaround concerns me. I would not know what potential problems would arise of providing this additional pathway, especially if something in the system fails. Of the thousands of people watching this video, I would be concerned about the few that end up doing the modification wrong. Perhaps Sequre can provide an official mitigation recommendation.
A bit confusing to show the problem with the use of a differential probe. A solitude DMM with 10MΩ impedance would do I think ? Still thanks for pointing it out.
Just a precaution as the Rigol scope is USB power also and although it has an earthed PSU it exhibits about 0.8Vac on the BNC shell relative to mains earth. I wanted full isolation to rule out any ground loops etc.
@@IanScottJohnston Yes, definitely lacking the experience you have, I still saw that it was because of the use of a scope to show us. But that is why I probably would use a DMM, to avoid the earth problem while measuring. For the educated viewer it is a fact, for the others it is a question what that differential thingy is....
NorthWestRepair who is in the US found similar voltage readings on the tips but in his case it was 50V AC due to lower mains voltage th-cam.com/video/xRht6uTDJAw/w-d-xo.html.
Yes, I saw that......and he's same opinion as me i.e. yes, it's a very low current, but would you really take the risk with your multi-thousand dollar GPU's!
1. See the video annotation @6:44 where I had confirmed the USB-A socket (shell) is connected directly right through to the tips, hence I didn't bother to show the final result on the multimeter.
th-cam.com/video/se6-jGZsHS0/w-d-xo.html
2. I have been in contact with Secure and they have promised to do something about this issue.
3. Why the Micsig?....Just a precaution as the Rigol scope is USB power also and although it has an earthed PSU it exhibits about 0.8Vac on the BNC shell relative to mains earth. I wanted full isolation to rule out any ground loops etc.
Hi Ian: A few comments if I may
01:10 If you live in the EU for example (as far more people do than live in the UK) then we only have two pin mains plugs, that are also reversable : So the grounding issue you raise is just a local one
02:10 We tried to reproduce this on the live stream a week ago and couldn't. Do you think it is due to the power supply you are using rather than the HT140 as we didn't use that one. Yes I know it is the supplied PSU but it can't drive the tweezers properly so we used a third party 140W supply. We also tried using a USB power bank with the HT140 and couldn't replicate this problem with that either, which is unsurprising as the power bank is not connected to the mains. Try using a USB power bank yourself and see what you find then let us all know if your results agree with ours. Also if you take a multimeter and measure the resistance between the two tips you will find that they are connected together (zero ohms) so you can't possibly have 300V between them 😉
05:39 - only if the device you are repairing is grounded! As general point, an electronics workbench should not be earthed it should be connected to an isolation transformer. This is because it is much safer. Use a grounded antistatic mat of course but that has a very high resistance (megaohms) to ground. So if your DUT, isn't grounded or plugged into the mains while you are soldiering (and why possibly would it be??) and the two tips of HT140 are connected to each other please elaborate how this can damage anything? This is not a criticism of your opinion, I'm up for a good discussion about it. Be nice to hear from you.
I am in the UK (Scotland actually, the better end!). I bought the HT-140 kit from Sequre and they supplied the PSU.
So far, it works fine irrespective if grounded or not. Yet to put it under heavy load but so far so good.
Here's my opinion:
This is not an issue of whether soldering iron tips should be floating or not, it's an issue of whether the workbench should have actual real leakage currents and capacitive coupled large voltages should be left to occur.
When you apply the iron tips to a PCB then one or both of them will come into contact with the PCB and depending on the potential the circuit is at and due to the leakage current / capacitive coupling a large potential between them MAY occur.
Saying that, if it is a floating circuit, i.e. not plugged in anywhere) then you are at the mercy of any floating circuits and the voltage potentials across the entire system may or may not do.
Example: I just grabbed a PCB and put it on the workbench (grounded EE bench mat so ESD not an issue). It's not plugged in anywhere, totally floating, and I just measured the voltage between the iron tips and an IC component leg on the PCB.
- Without blue cable earth fitted = 36VACrms
- With blue cable earth fitted = 2VACrms
The air in an around the workshop is having an effect of naturalizing/pulling floating voltages on circuits. So, it's better to have the iron tips earthed IMHO.
Better to take the issue out of the equation totally IMHO. If the tips were floating WITHOUT the leakage current / capacitive coupling problem then it would be much better......but they are not.
I haven't opened up the Sequre PSU yet, but suspect its a Y capacitor issue that's injecting primary --> secondary and finding its way to the tips.
The use of an isolation transformer is not mandatory on any EE workbench (I have one), just when they need arises I think most EE's will look at it.
I have been in touch with Sequre and they are looking seriously at providing a cable so users can optionally do what I did.
PS. I have two BM786 DMM's........the first one I tried during the making of the video turns out of found it had a blown 400mA fuse on the current circuit. One wonders why!
Ian.
@@IanScottJohnston Hi Ian
Yeah I figured you are from the better end of the UK 🙂. I'm originally from one of the less pleasant parts, Stoke-on-Trent, but in July 2016 I figured it was quite likely to get a lot worse and moved to the south of Gran Canaria.
Anyway, electronics, so for any current to flow anywhere between two potentials there has to be a current path. If the PCB you are working on is not grounded then no current can flow from the soldering iron tip into it, as at the instance the tip touched the PCB both become the same potential. Of course if there is some sort of capacitive coupling between the PCB you are working on and ground, and there is also an instantaneous current path from your soldering iron via the PCB to ground but only while that capacitance charges up
I have the same PSU with the HT140 as it was supplied with the review sample. I tried that one and also a 28V 5A PD3.1 supply and there is a notable improvement with the HT140 performance so I would honestly recommend you get a PSU rated at 28V 5A as it's well worth the money. I got a fairly cheap PD 3.1 supply from AliExpress and that does power the HT140 properly... with a few quirks (I'll publish a video on that soon)
I would suggest that anyone using a USB soldering iron of any sort, who is worried about earth leakage, just run it from a power bank and the problem is eliminated.
Re Isolation Transformer, it's not mandatory but it is a *very good idea* and has surely has saved me from dangerous electrical shocks on more than one occassion.
I'm sure you are totally correct that the floating potential is coming from a High Voltage (Y) capacitor in the PSU connected between the primary and secondary winding. The severity of this problem will vary from one PSU to another which may be why we couldn't replicate this issue. On another live stream we actually removed the Y capacitor from a small 'wall wart' SMPS to see what would happen. It continued to work just fine. Yeah I know it may cause high frequency noise on the mains wiring but we didn't notice any detrimental effect from doing so and doubt you would see any real world consequences from just removing it.
This issue is a potential problem with any USB powered soldering iron. Anyone using a USB soldering iron should take note.
The voltage and energy available in that leakage current could easily damage more sensitive devices such as RF FETs,
I don't think I have ever seen a USB wall wart with an earth ground connection. I wonder how many even connect the shield connection internally.
Thank you for bringing attention to this issue and offering a low cost solution.
Not the only USB irons, but most of cheap soldering devices with non-isolated switching PSU
I like to include some resistance in a soldering iron ground - just in case. With real transformers 1 Meg works. But you have a switcher so there will be current through the dreaded Y caps. 1 meg will leave a lot of volts on the tips, so maybe 1k.
I have seen soldering iron and soldersucker heaters breakdown due to element insulation. Pays to keep an eye on the leakage voltage.
I bought the same HT140 tweezers on aliexpress but without the 65W USB PSU. I am using a grounded 24V 100W PSU.
I plan to do same thing. I have old soldering station with 24V/60W transformer and plan to make simple linear PSU for that purpose.
4:12 It's interesting that the Vpp measurement is much more than the "normal" 2*Sqrt(2) * VRMS. Presumably this is because the waveform is quite non-sinusoidal. The ratio of these measurements does note even have the same ratio for unloaded versus loaded with 100k.
Distorted waveform and harmonics maybe.
Definitely 😅@@IanScottJohnston
I would have liked to see a verification step with the differential probe connected between the mains earth wire and the iron tips to see if that 100V AC on the tips has been pulled to ground. We don't actually know if the soldering tweezer tips are connected through to the USB shielding nor if the power supply is properly connecting the shields across the 2 USB ports
See the video annotation @6:44 where I had confirmed the USB-A socket (shell) is connected directly right through to the tips, hence I didn't bother to show the final result on the multimeter.
th-cam.com/video/se6-jGZsHS0/w-d-xo.html
@@IanScottJohnston Oh I'm sorry! I didn't notice that annotation! I was looking at your fingers touching the earth wire and not paying full attention to see the annotations
No worries, I have pinned this to the top of the comments also.....incase others have same query.
Even with that relatively high source impedance I can imagine even some low voltage capacitors would not be really happy if they caught the full peak voltage, never mind silicon devices.
Humm interesting, I’m in the US and our neutral is bonded to ground in our main panel I’m wondering if I would see the same thing or that bond would be enough? I may need to check this out!
Whats the situation with the barrel jack, is -ve/chassis connected to it?
The same problem is to TS80
Hi Ian, does the temperature control still works correctly ?
I have seen on a soldering station review that wasn't grounded, that the temperature went above 440° C while the set temperature was only 360° C.
This was caused when soldering on a grounded circuit.
The video where this can be seen :
th-cam.com/video/B7jLpHgR7fI/w-d-xo.html
Appears to work just fine.
I have seen wierd issues when temp sensors/probes are wired incorrectly/backwards, i.e. offsets and the like.
I like the weller soldering stations where the tip connection is via a jack socket. So you can short the tip to ring in the plug and once plugged in ground the tip, or it allows you to fit any value resistor you want. I like a 10k resistor nice pull down to earth for leakage but will not pull too much current if you decide to work on with some voltage still present after turning off.
Looks like I might have to see if santa has any money left over, as the covid-19 like present he gave could not have been too expensive 😂😢. Went down on the 25th and the shi* is still working its way out 😢
Sorry to hear you've been subjected to the dreaded lurgy........I prescribe you a week in your workshop. Usually helps all ailments!
@IanScottJohnston thanks doc.😄
Another option is to leave the USB cable whole and create a USB-Banana adapter with a resistor of choice. However, doing this type of workaround concerns me. I would not know what potential problems would arise of providing this additional pathway, especially if something in the system fails. Of the thousands of people watching this video, I would be concerned about the few that end up doing the modification wrong. Perhaps Sequre can provide an official mitigation recommendation.
I have been in contact with Sequre, they have seen my video.......and have promised to do something.
A bit confusing to show the problem with the use of a differential probe. A solitude DMM with 10MΩ impedance would do I think ?
Still thanks for pointing it out.
Just a precaution as the Rigol scope is USB power also and although it has an earthed PSU it exhibits about 0.8Vac on the BNC shell relative to mains earth. I wanted full isolation to rule out any ground loops etc.
@@IanScottJohnston Yes, definitely lacking the experience you have, I still saw that it was because of the use of a scope to show us. But that is why I probably would use a DMM, to avoid the earth problem while measuring. For the educated viewer it is a fact, for the others it is a question what that differential thingy is....
NorthWestRepair who is in the US found similar voltage readings on the tips but in his case it was 50V AC due to lower mains voltage th-cam.com/video/xRht6uTDJAw/w-d-xo.html.
Yes, I saw that......and he's same opinion as me i.e. yes, it's a very low current, but would you really take the risk with your multi-thousand dollar GPU's!