Author Topic: Modifying the KSGER T12 to make it safe  (Read 748 times)

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Offline snoopy

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Modifying the KSGER T12 to make it safe
« on: September 22, 2019, 03:06:55 am »
Much has been written about the KSGER and how it is an economical alternative to the name brand soldering stations. However one of its Achilles heals is it's electrical safety which is potentially dangerous, and would fail the appropriate electrical tests. I now have three of them and two have replaced the Hakko FX-951 stations which are very inflexible to use. Two of the KSGER's are the cheaper plastic case variety and the most recent purchase is the aluminium case variety which is the one I have modified for this example. Apart from earthing the metal case the procedures for improving safety are the same. All three have 2.0.9 firmware and 2.00S hardware revision. The newer versions may already have improved safety. You will have to check.

Remove the top cover. The plastic case version is a bit trickier as it requires the removal of the stick-on front panel to get to the front screws.

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First thing is to remove the main PCB from the chassis.

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Next is to remove the heatsink and transistor for the secondary side of the switch mode power supply. This is the larger of the two heatsinks.

You need to trim a bit of the heatsink with a suitable pair of cutters where it crosses the primary side pcb trace so there is a reasonable amount of creepage.

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Also I added some plastic washers under each of the soldering posts on the heatsink which gave an additional 0.5mm of standoff from the board,

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Now note how the heatsink no longer crosses the mains trace on the PCB.

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I added a heavy duty earth wire from the mains earth connection directly to the secondary negative supply rail.

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I also added a screw post to earth the metal case and hard wired it to the earth connection from the mains input. You may have to scrape the screws with a suitable wire brush to make good contact between the various parts of the metal chassis so it is earthed properly.

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« Last Edit: September 22, 2019, 03:10:25 am by snoopy »
 
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Offline floobydust

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Re: Modifying the KSGER T12 to make it safe
« Reply #1 on: September 22, 2019, 03:33:36 am »
Looks much better  :)
I'm lazy and put Kapton tape over the HV PCB trace that runs under the heatsink.
I soldered a ground wire to the encoder's tab, to ground the aluminium case instead of drilling a hole.
PSU trace pic and schematic: https://www.eevblog.com/forum/reviews/t12-stm32-v2-1s-soldering-station-controller-schematic-etc/msg2467236/#msg2467236
 
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Offline BlackICE

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Re: Modifying the KSGER T12 to make it safe
« Reply #2 on: October 02, 2019, 08:01:59 pm »
I understand why grounding the case and minimizing the chance that the heatsink shorts the HV traces, but what is the purpose of grounding the secondary's ground to earth ground. Yes the secondary potential may float to some higher voltages relative to earth ground, but it doesn't present a danger to the user since if a malfunction occurred it would short out to the case or tip before harming the user. However grounding it may help minimize the internal damage to device if something were to go wrong.
« Last Edit: October 02, 2019, 08:04:06 pm by BlackICE »
 

Offline BlackICE

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Re: Modifying the KSGER T12 to make it safe
« Reply #3 on: October 03, 2019, 12:11:21 am »
I made finished the mods to mine. Added a ground wire from the IEC connector to the rotary encoder and removed and cut the a fin from the heatsink. I also mounted the heatsink higher by about 1 to 1.5mm. In doing the heatsink mod I don't think it is really necessary from a user safety viewpoint under normal use. Even if somehow the HV went through, or jumped over the solder mask to the heatsink isn't electrically connected to anything else. As long as the cover grounded and installed any problems with the HV reaching the heatsink will be container inside the enclosure.

BTW I used to use solder wick and a spring loaded solder sucker they are a PITA. Because I now have a Hakko FR-301 it made the mods much easier to do.
 

Offline totalnoob

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Re: Modifying the KSGER T12 to make it safe
« Reply #4 on: October 03, 2019, 01:48:55 am »
I made finished the mods to mine. Added a ground wire from the IEC connector to the rotary encoder and removed and cut the a fin from the heatsink. I also mounted the heatsink higher by about 1 to 1.5mm. In doing the heatsink mod I don't think it is really necessary from a user safety viewpoint under normal use. Even if somehow the HV went through, or jumped over the solder mask to the heatsink isn't electrically connected to anything else. As long as the cover grounded and installed any problems with the HV reaching the heatsink will be container inside the enclosure.

BTW I used to use solder wick and a spring loaded solder sucker they are a PITA. Because I now have a Hakko FR-301 it made the mods much easier to do.

I question this as well.  I admit, I am not an electrician or an electrical engineer, only a DIY hobbiest, but I have wired up my workshop to code, so I know enough about electricity to be dangerous to myself and others  :-DD.  Anyway, my first concern, being in the US and falling under the auspices of the NEC, my workshop has GFCI's protecting all 120V outlets.  I know that we are talking about electronic voltages and probably low amps, so this may not be enough to trip a GFCI, but has anyone used this mod on a GFCI circuit, and did it trip or not?  Second, BI, you pointed out a flaw that I was going to, and that is should something go wrong and the hot or neutral short to ground, and this is admittedly a very long shot, you would then have primary voltage potential at the soldering iron and if it happened to be the hot "lug" prior to the switch, the soldering station would not even need to be on for this to happen, as long as its left plugged in, there would be primary potential on the hot leg and if it were shorted to ground, at the electronic voltage side as well.  Again, I'm not someone with deep electronics or even electrical knowledge, but it just seems like running a ground from the primary side to the secondary voltage (i.e. the electronic voltage) side defeats the idea of the isolating the primary from secondary.  :-//

But, grounding the case is a great idea.  It should be ground at the higher potential.
 

Offline BU508A

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Re: Modifying the KSGER T12 to make it safe
« Reply #5 on: November 02, 2019, 06:08:52 pm »
A friend of mine asked me for a cheap but reasonable soldering station, so I recommended him the KSGER T12.
I've found this thread (thanks to the OP) and want to share here my mods to increase the safety of the 230V~ model.

After pulling the diode with the heatsink, I've applied some Kapton tape and corrected the tilted green capacitor.


I've also applied some Kapton on the heatsink as well, just for paranoia reasons.


Putting everything back together and left some space between heatsink and PCB (paranoia, you know?)


I took a closer look and found two places, where the space between the connectors is not enough (imo)

This is the rectifier on the mains side:


This is the connector where the mains come in. Earth ground is in the middle.


I cleared the spaces between the connectors with some diamond tools:


Mains connector (white) and the mains rectifier.


Wires soldered:


Everything reassembled, just an overview:


I hope you may find this helpful.

Cheers,

Mounty


« Last Edit: November 02, 2019, 06:14:35 pm by BU508A »
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