Soldering station Quicko T12-943 no power - Page 1
Forum section: electronics / beginners

author: draza
author_rank: Newbie
timestamp: April 29, 2019, 07:00:18 pm
content: Hi everyone,I am electronics beginner who bought this little soldering station from Aliexpress ten days ago. I was very pleased with her until she stopped working today.After opening, I noticed something strange, and I have a question about it.The station is powered by an external power supply 16-24v DC 3A(i have cheap D.C. variable bench supply 0-30v 5A, switch-mode).The question is: What does the resistor do on the DC internal connector between + and - line?What could be the problems not powering anymore?Thanks in advance.

author: bdunham7
author_rank: Super Contributor
timestamp: April 29, 2019, 10:51:21 pm
content: The resistor is not likely your problem, it looks like it is just a bleed-off shunt or ballast. The colors in your photo are off enough I can't determine the color bands, but just measure the resistor quick and let us know what it is--likely a few dozen k-ohms or so.As for it not power up--it looks like the display is on??? Or is that a before-failure picture?

author: KL27x
author_rank: Super Contributor
timestamp: April 30, 2019, 04:21:00 am
content: Presumable reason for the resistor is to put some minimum sort of pre-load on the powersupply. Your lab supply is probably fine without it, but some other PSU might have increased noise at low current draw and/or the voltage might drop significantly when the heater turns on and the current draw increases.

author: draza
author_rank: Newbie
timestamp: April 30, 2019, 07:17:05 am
content: The resistor is 1k, voltage comes to the board. Here's another picture of the board itself.The last picture is before sudden death.

author: bdunham7
author_rank: Super Contributor
timestamp: April 30, 2019, 03:02:28 pm
content: OK, so details matter in troubleshooting as we aren't there to see it. Brevity is not helpful!If I understand you, you have power voltage measured at the top two terminals where the red and black wires plug into the board, presumably measured by backprobing at those two terminals? And the device now shows no signs of life whatsoever, no display, no nothing?To answer your original question, the resistor would appear to have nothing to do with the problem.

author: floobydust
author_rank: Super Contributor
timestamp: May 02, 2019, 04:08:10 am
content: OP, check your 3.3V voltage rail. I think the buck-converter has SMT marking code SYTB and possibly a knock off ofLM2841XBMKX.The seemingly useless power resistor could be for damping voltage spikes due to the heater switching on/off and cable inductance to the laptop adapter etc.edit: it's because the 24V PSU needs a minimum load current (i.e. when heater is off) to keep regulated.

author: draza
author_rank: Newbie
timestamp: May 02, 2019, 09:30:47 pm
content: Thanks for the advice, I'll check it. I hope it is not a microcontroller.

author: bd139
author_rank: Super Contributor
timestamp: May 08, 2019, 02:11:22 pm
content: Mine exploded. Check the tip doesn't short anything out in the handle if you push it in and out. That's what finished mine off.

author: floobydust
author_rank: Super Contributor
timestamp: May 08, 2019, 06:08:07 pm
content: What exploded? The P-ch mosfet?

author: bd139
author_rank: Super Contributor
timestamp: May 08, 2019, 07:13:30 pm
content: Yep. Blew right out.

author: Specmaster
author_rank: Super Contributor
timestamp: May 08, 2019, 07:39:21 pm
content: Just maybe, it's an issue with the 943 controller board? When I got my second T12, I decided to try out another controller board so I purchased on from Banggoodhttps://www.banggood.com/T12-Digital-Soldering-Station-OLED-Display-Control-Board-STC-Controller-Kit-p-1140746.html?rmmds=myorder&cur_warehouse=CNand that one after a few weeks suddenly developed a fault that caused the tips all to glow cherry red. After I purchased the replacement controller from Aliexpress, the one as used on the Quicko T12-952 and fitted it I've had zero problems with either of them.

author: floobydust
author_rank: Super Contributor
timestamp: May 08, 2019, 07:44:06 pm
content: Gotta hate that.22P04 -40V -22A (DPAK)TPC8107 -30V -13A (8 pin) no margin for short circuits.It's tough, a real Hakko FX-951 is $400 CAD at Digikey and the alternatives from guangdong are a PITA.I see a bunch of the 24VDC PSU's used in the knock-off T12 stations have added 1k dummy load resistors here and there.The PSU's are not the greatest and Vout spikes up when there is no heater load. Some don't even use TL431.

author: bd139
author_rank: Super Contributor
timestamp: May 08, 2019, 07:47:00 pm
content: Yep. SOA is exceeded pretty quick on any MOSFET at Rds(on) of 0.2 ohms. Why I call them MOS-PHUTs. I've blown up tens of IRF510's trying to use them as RF PAs. They go with one hell of a crack.I bought a nice iron made in China in the end. A Metcal PS900

author: Specmaster
author_rank: Super Contributor
timestamp: May 08, 2019, 07:52:24 pm
content: Guys, I have updated my original post a couple of posts above.

author: Haggis McHaggis
author_rank: Contributor
timestamp: May 18, 2019, 11:44:48 pm
content: @drazaThat's a pity, i feel for you. I hope there is no immanent problem with this controller boardDo you have any news on this?

author: Specmaster
author_rank: Super Contributor
timestamp: May 19, 2019, 12:35:01 am
content: This is the third T12-943 that I know of that has failed and I'm beginning to wonder if it isn't either the power supply not being stable enough or the actual controller itself. I know that there are other forum members who also use T12 and they are happy with their setup's just like I am with my two. Personally I'd cut my losses on the 943 and invest in the T12-952 complete with supplied Power Supply.

author: Haggis McHaggis
author_rank: Contributor
timestamp: May 20, 2019, 10:27:51 am
content: Quote from: bd139 on May 08, 2019, 02:11:22 pmDo you mean changing the tip while the unit is powered can cause a short?

author: Specmaster
author_rank: Super Contributor
timestamp: May 20, 2019, 11:15:41 am
content: While that should not be possible, it has to said that not all the handles are equal in their construction qualities and likewise with the tips themselves, many have poor contacts and changing tips all the time can cause these contacts to fail completely and cause shorts. I have had some issues with my tips with the contact rings on them coming undone. This one of the reasons why I ended up getting 2 stations so I could keep different tips in each and then use which ever one best suited my soldering requirements at the time and thus minimise the possibility of a short that could blow the Mosfet. I keep a K and C4 tip in my handles for almost all of my work and it works really well.

author: floobydust
author_rank: Super Contributor
timestamp: May 20, 2019, 08:02:07 pm
content: I mentioned in another T12 thread:Quicko says T12-943 must be limited to 25VDC max. input voltageSo any overshoot or surges might be too much.Some of the low cost 24V PSU's have extra 1k load resistors, but who knows what voltage the PSU gives at light load (heater off).There is a high risk if the DC adapter (or bench PSU) is already on and then you plug it (DC) into the soldering station,a surge occurs that can make an overvoltage spike and damage the controller.It's due to the cable inductance and capacitors. Best to plug in AC power last.

author: Haggis McHaggis
author_rank: Contributor
timestamp: May 20, 2019, 08:10:22 pm
content: Should we install a voltage peak protection then? If yes, what circuit should be used? Is there a cheap ready made module available for this?

author: Haggis McHaggis
author_rank: Contributor
timestamp: May 21, 2019, 03:02:52 pm
content: Quote from: floobydust on May 20, 2019, 08:02:07 pmThere is a power on/off switch on this device. Is this switch going to cause the same issue when the DC adapter is already plugged in? If yes, this switch would be a bad idea and should be removed, right?

author: floobydust
author_rank: Super Contributor
timestamp: May 22, 2019, 01:31:08 am
content: Where is the on/off switch - in the brick or at your soldering station?You want to avoid the laptop adapter is powered on making 20V, and then you plug in the DC jack to the soldering station.The capacitors in the brick dump into the soldering station and create a surge.I don't know which components are delicate on the T12-943. Perhaps Quicko is using 25V capacitors on their 24V controller, or a 30V IC.For surges, a big TVS diode like1.5KE27Aat the DC jack is what I would consider. A TVS diode cannot allow 24V but clamp to 25V. Their clamping ratio is not so tight.

author: Haggis McHaggis
author_rank: Contributor
timestamp: May 22, 2019, 09:04:57 am
content: Quote from: floobydust on May 22, 2019, 01:31:08 amOn the soldering station. You can see the switch on the first photo in the opening post (Quicko resistor to switch.png)

author: Specmaster
author_rank: Super Contributor
timestamp: May 23, 2019, 05:43:43 pm
content: As floobydust mentioned in an earlier post and on your other thread (not too sure why you opened another thread for this),Quicko says T12-943 must be limited to 25VDC max. input voltageand the type of PSU you are using has low current AC voltage of upto 90V leaking onto the DC output and it is this that has possibly caused your problem.As I mention on the other thread, I believe the solution is either feed the iron with pure 24V from a battery or to replace the whole unit with a Quicko T12-952 with the dedicated Quicko PSU built in the case.

author: floobydust
author_rank: Super Contributor
timestamp: May 23, 2019, 05:59:04 pm
content: We don't know what Quicko T12-943 parts are failing, draza did not mention.Let's assume it is sensitive to overvoltage transients on DC power. The DC on/off switch would cause a power on spike and is trouble. Consider:LT AN88 Ceramic Input Capacitors Can Cause Overvoltage Transientsfor detailed analysis and notice the spikes can approach 41Vpk.

author: Haggis McHaggis
author_rank: Contributor
timestamp: May 23, 2019, 05:59:44 pm
content: Quote from: Specmaster on May 23, 2019, 05:43:43 pmThis is not my thread, draza opened this topic and posted about it in my thread.These topics are related to some degree. I've no idea why draza is not attending anymore. Would be intresting to hear what the problem was and what can be done to prevent it.What i want to do is preparing everything before going to use the station in the best possible way and learn something about grounding/ESD.

author: Specmaster
author_rank: Super Contributor
timestamp: May 23, 2019, 06:05:56 pm
content: Quote from: Haggis McHaggis on May 23, 2019, 05:59:44 pmIn that case I apologise, I never spotted that theOPwere two different members but still firmly believe that the solution to one is the same for other as it only seems to the 943 variant that has these issues, in view 952 is the way to go.

author: Haggis McHaggis
author_rank: Contributor
timestamp: May 23, 2019, 06:15:47 pm
content: Quote from: Specmaster on May 23, 2019, 06:05:56 pmDon't apologise. I'm thankful you and other participate and offer help for beginners like me.I'm already in the process of ordering a second station, but not sure i should get the 951 (LED) or 952 (OLED) version. I think the LED version could be enough, but who knows.Nevertheless i want to use the station i already have and want to understand the best grounding method. I wasn't aware that these laptop psus are bad or cheaply designed. They cost a fortune after all.

author: Haggis McHaggis
author_rank: Contributor
timestamp: May 23, 2019, 06:44:28 pm
content: Quote from: floobydust on May 23, 2019, 05:59:04 pmThanks for the document. I overflew it, but unfortunately it's beyond my skills to design a solution from it. The 1.5KE27A you mentioned is probably more realisitic for me. But even with the diode i struggle to choose the right part. I can't interpret the datasheet properly. I think i need a uni-directional type. Would the 1.5KE22A or 1.5KE24A be the right part for this application? My psu is 20VDC.

author: floobydust
author_rank: Super Contributor
timestamp: May 24, 2019, 01:52:04 am
content: You want a TVS that does nothing at 20V (or 24V) yet clamps below the point of damage to the controller. SMD marking code SYTB I couldn't find, it might be an LM2841 max. 45V input. So a 22A or 27A TVS is OK.Notice app. note 88 also shows adding a bulk capacitance 47uF 35V works very well.I would put in both the TVS and capacitor, like this schematic.The Quicko "STM32 T12" controller, I notice the ads on Ali are no longer showing this controller in the T12-943 stations.It seems to be replaced by the "T12-952 STC OLED" which is back to using a linear voltage reg.

author: Specmaster
author_rank: Super Contributor
timestamp: May 24, 2019, 06:21:18 am
content: The T12-952 controller is same one I have in my stations and I’m happy with their performance.

author: Haggis McHaggis
author_rank: Contributor
timestamp: May 24, 2019, 07:51:25 pm
content: Quote from: floobydust on May 24, 2019, 01:52:04 amThank you very much for the schematic. Much more than i could ask for.

author: draza
author_rank: Newbie
timestamp: May 28, 2019, 09:26:46 am
content: Sorry,I was very busy these days.What I found was that S4 Schottky diode isshorted, I do not have a suitable replacement. No voltage on CPU.The SYTB is step-down DC / DC regulator chip (LM2841XBMKX).Does anyone know what this 541IG ic is?

author: Specmaster
author_rank: Super Contributor
timestamp: May 28, 2019, 10:01:17 am
content: I did a google search and cannot find any data on this IC at all so I did a image search and came up with this test of a USB charger meter that uses the same IC and there author seems to think that this is indeed an op-amp ?https://lygte-info.dk/review/USBmeter%20RD%20Tech%20USB%20Meter%20AT34%20UK.htmlEDITI just did a search for 5411G (thinking that the I could be a badly printed 1) and bingo, I have the data sheet for this IC which would appear to a voltage detector with built delay circuit and is set at 4.1V.

author: floobydust
author_rank: Super Contributor
timestamp: May 28, 2019, 07:47:24 pm
content: Buck-converter diodes failing short has been talked about in this thread:https://www.eevblog.com/forum/projects/interesting-failure-of-buck-converter/SMT marking "S4" is a Schottky diode SOD-123 package, like a 1N5819 (B5819) orSD103AW40V 0.2AThese controller boards have the absolute minimum capacitance to just work, and this PCB does not look so great especially the ground pour and putting a high gain op-amp next to the noisy buck converter. I can't see the temperature reading being stable.Other controller designs use a buck-converter then a 3.3V LDO for quiet power.The SOT23-5 IC is the thermocouple amplifier, usually a LM321-clone op-amp like SGM8551.SMT marking "541I" I could not find SOT23-5 parts, it might be a clone of AD8541 (A4A marking).