No transformer in Soldering station? - Page 1
Forum section: electronics / general

author: moboch
author_rank: Contributor
timestamp: August 03, 2019, 08:30:24 am
content: So I took a look into my Soldering station yesterday because I was wondering how it can be so light. It literally weights almost nothing. Anyway inside of it there only was a PCB that's about 4x5cm big/small.On it only was a 16 pin chip and a bunch of complementary components. Then I started googleing and found out that basically all Soldering stations have a transformer. My station was really cheap like $50, but now I'm wondering is it safe to use?Thank you for all answers.

author: madires
author_rank: Super Contributor
timestamp: August 03, 2019, 08:42:34 am
content: Please post some pictures of the PCB!

author: Ian.M
author_rank: Super Contributor
timestamp: August 03, 2019, 08:49:41 am
content: ... and the mains lead + plug (both ends), and the handpiece and the wiring from its connector on the station to the PCB.There's nothing preventing a properly designed station with a mains voltage heating element meeting all applicable safety standards, but there are lots of ways for cheap and nasty far east manufacturers to FUBAR their design so its unsafe.

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 03, 2019, 08:59:14 am
content: this is pcb of yihua 938D soldering tweezer, i suspect 908D iron also the same. so yes heater (or fan if any) is directly to mains. but i guess they are isolated and will be fine as long as the external metallic body is grounded. i checked mine to be grounded.

author: moboch
author_rank: Contributor
timestamp: August 03, 2019, 09:32:32 am
content: This is the PCB. Sorry, I didn't want to take it out completely I Hope you can see it well enough. At the top you see the mains in ( European plug with PE) and under the PCB there is the output to the heater.

author: Shock
author_rank: Super Contributor
timestamp: August 03, 2019, 10:49:26 am
content: You should at least take a photo or tell us what it is. I'd say if it was $50 bucks of Chinese soldering station you got ripped off.Looks like capacitive power supply circuit. If it's not been tested properly or certified it may be considered illegal regardless of how safe it is. If you brought it direct from China or from seller that is sourcing from China you can almost assume it's not been tested properly for safety.

author: madires
author_rank: Super Contributor
timestamp: August 03, 2019, 11:22:07 am
content: I agree, could be a capacitive dropper for the MCU and the white DIP seems to be an optocoupler. I guess there's a TRIAC on the other side.

author: Ian.M
author_rank: Super Contributor
timestamp: August 03, 2019, 11:43:59 am
content: Check continuity from the mains plug PE to the soldering iron tip. If its more than a couple of ohms its unsafe. It would also be unsafe if used with a wall socket that hasn't got a (properly connected) PE contact, or isn't on a RCD protected circuit.To further assess its safety we'd need good in-focus square-on closeups of both sides of its PCB, and of any markings on the brown capacitor and the suspected TRIAC.

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 03, 2019, 12:39:12 pm
content: Quote from: madires on August 03, 2019, 11:22:07 amalmost certainly is. if someone loves horror movie, he can have a look on the bottom pcb side attached (look at topmost trace) and go bite pillow in the corner of the room. kettle has direct mains heater under it, go dismantle if more horror movie is needed. for all i know, that circuitry will go direct to heat element (ceramics insulated) if any concern, thats where should be analyzed... the yihua's cost about $20-40, ymmv.

author: Chernig0v
author_rank: Newbie
timestamp: August 03, 2019, 06:10:08 pm
content: This circuit is not 100% galvanically isolated.Be sure to have grounding and leakage protection on the case!

author: moboch
author_rank: Contributor
timestamp: August 03, 2019, 09:15:49 pm
content: Bought it on Amazon. It was shipped from Germany but I think it's still a crappy Chinese product.

author: moboch
author_rank: Contributor
timestamp: August 03, 2019, 09:18:55 pm
content: Quote from: Ian.M on August 03, 2019, 11:43:59 amThe resistance is 1.2 Ohms but the screws from the case are not earthed in any way

author: Ian.M
author_rank: Super Contributor
timestamp: August 04, 2019, 12:02:10 am
content: Unearthed exterior metalwork that penetrates the case without reinforced insulation between it and the interior wiring and circuit board is also unsafe. I would strongly prefer a properly grounded metal case or a plastic case with no exposed exterior metalwork that penetrates to the interior. You may need to add more grounding inside the case for the screws etc. to make it reasonably safe.

author: Shock
author_rank: Super Contributor
timestamp: August 04, 2019, 03:03:49 am
content: Moboch, as I said before share a photo of it so other people can avoid buying.

author: Ian.M
author_rank: Super Contributor
timestamp: August 04, 2019, 11:19:09 am
content: The only photo the O.P. posted ishttps://www.eevblog.com/forum/reviews/no-transformer-in-soldering-station/?action=dlattach;attach=801888It would be nice to see some exterior photos as well so we can assess the risks of the ungrounded metalwork properly.The switch body needs grounding. Grounds *SHOULD* be made with crimped ring terminals on a dedicated stud, as fixing screws can come loose, and solder joints can fail in various ways, but I'd be a *LOT* happier with a ground wire soldered to the side of the switch body rather than no ground at all.The bolts on the right side could easily be covered with epoxy putty or acid-free silicone caulk to insulate them.I don't know what's going on with the apparently metal fingers visible on both sides at the back of the photo. What are they part of? If its a tray for a sponge, careful sealing with silicone caulk to prevent water penetration and also insulate them would be advisable, as they are unlikely to be a soldereable metal so it will be difficult to ground them.

author: moboch
author_rank: Contributor
timestamp: August 04, 2019, 07:57:45 pm
content: Here's a photo from the outside and an Amazon linkhttps://www.amazon.de/Holife-Premium-L%C3%B6tstation-LED-Temp-Anzeige-Temperatursperrfunktion-Schlaffunktion/dp/B079ZN6Q2F/ref=mp_s_a_1_1_sspa?keywords=holife+solder&qid=1564948575&s=gateway&sr=8-1-spons&psc=1Quote from: Ian.M on August 04, 2019, 11:19:09 amI don't know what bolts you mean.

author: Ian.M
author_rank: Super Contributor
timestamp: August 04, 2019, 08:11:54 pm
content: So, what I thought were metal fingers are actually the ventilation slots back-lit. The bolts hold the solder reel dispenser. Ground them (both) or insulate them, whichever's easier. The switch is fairly low risk as its screw heads are covered, but I'd still go with my suggestion of soldering a ground wire to the side of its body.A close inspection of the iron (handpiece) itself would be a good idea, including dismantling it to check security of connections and insulation.

author: moboch
author_rank: Contributor
timestamp: August 04, 2019, 08:22:50 pm
content: Quote from: Ian.M on August 04, 2019, 08:11:54 pmIt seems to be a fairly simple Heater/Thermocouple combo, but it's missing any proper isolation considering it's dealing with 240v

author: Ian.M
author_rank: Super Contributor
timestamp: August 04, 2019, 08:50:03 pm
content: I've seen worse. At least its got glassfibre sleaving on the wires that are expected to get hot. You haven't taken the board out far enough to see the cord grip.It should be OK as long as the handle and element are undamaged. Stop using the iron immediately if you discover a crack in either.