Youyue 858D+ teardown - Page 1
Forum section: electronics / general

author: madworm
author_rank: Frequent Contributor
timestamp: November 21, 2013, 12:19:19 pm
content: I got this device for 38€ delivered. Except one possibly fatal issue, it looks rather nice. You may guess what bothered me.I tried to replace the wire, but the heater tube is made from non-solderable material, so I ended up redoing the lousy thing exactly as it was.They used spade connectors in the main unit (even self-locking), so why not here as well?You can find more imageshere.

author: amyk
author_rank: Super Contributor
timestamp: November 21, 2013, 12:37:18 pm
content: "Youyue"These things get rebranded with the silliest names...Surprised the MCU is socketed; what is it?Be careful, there is live mains voltage on the main unit male pins when it's switched on

author: madworm
author_rank: Frequent Contributor
timestamp: November 21, 2013, 12:49:41 pm
content: The MCU is an ATmega8. I didn't find an ISP header. Otherwise I would've tried to read its firmware :-)You're right, I hadn't even thought of the connector!Some other models have the cable permanently attached. With respect to line voltage that is a bit safer. They should've used a connector with pins on the cable to reduce the chance of touching the potentially live ones on the base station.I'm starting to suspect that this device might not have been tested for safety too hard. Which is a bit odd... the HV slots look proper, isolation on spade connectors... and then they use the wrong connector for the wand...Maybe this thing was botched together from bought components. The components are fine on their own, but the combination is not always ideal as far as safety is concerned.

author: ddrl46
author_rank: Regular Contributor
timestamp: November 21, 2013, 01:30:45 pm
content: May I ask where you got this hot air station?

author: madworm
author_rank: Frequent Contributor
timestamp: November 21, 2013, 01:40:03 pm
content: Ebay. The seller is named 'troyexporter'.Regarding the wand connector. Yes, it is true. Once the switch is on, one of the pins potentially is live. 50/50 chance, as the AC plug in the EU (CEE 7/7) is not necessarily polarized. If you're in France, you should be a bit safer, not so in Germany.I added a big fat "! DANGER HV !" sticker next to the plug. Hopefully it will prevent me from being stupid. Maybe I should get an isolation transformer - just in case.On the bright side, they could've wired it up worse, i.e. a permanent (unswitched) connection to the front-side connector. Luckily they didn't do that.

author: fluxcapacitor
author_rank: Frequent Contributor
timestamp: November 21, 2013, 02:14:40 pm
content: The capacitor placement doesnt look very good.The one next to C17 is overlapping U6 and C17and might be touching R4.The cap below R18,R19 is bent over onto something ? ,a mosfet i think.The cap at C2 could do with a bit of extra solder on the pad.All the electrolytics are a junk brand,its worth swapping them for some decent ones.

author: Dawn
author_rank: Regular Contributor
timestamp: November 22, 2013, 06:45:37 am
content: I suppose things must be getting pretty bad when the Chinese are knocking off another Chinese knockoff brand.

author: amyk
author_rank: Super Contributor
timestamp: November 22, 2013, 07:56:37 am
content: Quote from: madworm on November 21, 2013, 12:49:41 pmThe usual Chinese attitude towards safety seems to be "don't act like an idiot"... meaning in this case "don't turn it on without the cord connected and go touching the pins".

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: November 23, 2013, 06:21:54 am
content: It's quite possible that it won't output any voltage without the "gun" connected...If there's no temperature sensor feedback, it might shut the output off completely.

author: amyk
author_rank: Super Contributor
timestamp: November 23, 2013, 06:36:41 am
content: Quote from: AmmoJammo on November 23, 2013, 06:21:54 amThe open-sensor failure mode on these (i.e. no voltage on thermocouple input) tends to be full power...

author: madworm
author_rank: Frequent Contributor
timestamp: November 23, 2013, 08:55:28 am
content: Quote from: amyk on November 23, 2013, 06:36:41 amThat would be nice, but as you can see, there is NO relay in there to disconnect mains voltage from the output. Just the TRIAC is not sufficient IMO.As this device runs with an ATmega8 chip, I'm thinking about writing a custom firmware for it. Reading the buttons / potentiometer / fan-control should be trivial. Driving the display and reading the temperature correctly (cal?) would be the 2nd step. If that works, I will have to deal with the HV stuff.One of the issues with this device is that it shows the temperature set-point and not the true value - unless you put the wand into its holder (quite braindead).I do see the point of "don't be an idiot and touch the pins...", but as everybody knows, sometimes the brain doesn't work correctly and shit happens.