W.E.P / YIHUA 852D+ combined hot air station and soldering iron

[Fraser]

W.E.P 852D+ Combined Temperature controlled Hot air station and soldering iron.

Available Ex. UK stock at less than £80 via e*ay.

In the Atten 858D+ hot air station review forum thread I commented that I have a W.E.P 852D+ that is also good value for money and performs well. A comment from RUFUS led me to delve inside to investigate the 852D+ design and some possible safety issues. Here is a précis of what I found.

The internal PCB designations suggest that the W.E.P 852D+ is actually a YIHUA 852D+.

1. The general construction method is acceptable with the wiring loom cable tied in place and connectors secured with sealant.

2. The mains input is fused in the Neutral line only - not good practice IMHO.

3. The units internal PCB's consist of two that are from other W.E.P products and one that is just for the 852D+... YH850V8 for hot air, YH936AVI for the soldering iron and the custom YH852V1.2 display PCB.

4. The YH850 PCB provides the power and control for the hot air heater and diaphragm pump. It derives its low voltage from the mains via dropper resistors and a regulator circuit. The control circuit for hot air temperature is an analogue thermocouple loop controlling a BT137 TRIAC that is fed from the mains supply. The heater is supplied with the chopped mains output of the TRIAC. The air pump speed control is also via a BT137 TRIAC.

5. The YH936 PCB is an analogue temperature controller for the 24V soldering iron. The control circuit is a thermocouple loop controlling a TRIAC at low voltage. Power for the YH936 PCB is derived from a main transformer that provides 24V.

6. The YH852 PCB contains a microcontroller and two LED displays. The microcontroller is fed with potentiometer position information from the hot air and soldering iron temperature controls. ADCs are used to produce a digital 'temperature' display. The display is potentiometer position related only and is in no way connected with the thermocouple temperature control loops on the YH850 or YH936 PCB's . The YH850 and YH936 temperature calibration trimmers are set to correlate with the displayed temperature but no calibration loop exists so drift is possible. LED's from the YH850 and YH936 PCBs indicate heater activity. The design of this PCB is not that unusual and appears similar in principle to the HAKKO 850B that also operates without a transformer and uses an analogue temperature control loop driving a TRIAC.

7. The 852D+ safety earth is connected at two points only. The case is directly connected to the mains feed cable Earth conductor and this is then extended to the YH936 soldering iron PCB where it effectively earths the soldering iron tip and shroud. There is no safety earth connected to the hot air hand-piece metal shroud. This gives me cause for concern as the heater element within the metal shroud is fed with chopped mains voltage from a TRIAC.
The diaphragm pump appears well built and produces a good constant flow of air via its attached reservoir. Noise levels are very acceptable at all air flow rates.

Temperature accuracy has yet to be measured and will be added to this posting shortly.

This completes the brief description of the W.E.P 852D+ hot air workstation internal modules.

[Rufus]

Can of worms isn't it. Wonder how many Chinese factories make these things sticking their or someone else's name on the front and why do they need to sort of clone the model numbers?

Anyhow good job on the review and photos.

Fusing the neutral and not live is bizarre and not earthing the heater shroud is grim. Does it look feasible to stick an earth wire up the air pipe? Is there a tag on the shroud to connect it to anyway?

 

[Fraser]

Hi Rufus

No tag on my shroud. I believe they are relying on the thermal insulator around the heating element but that doesn't constitute 'double insulation'. I shall be spot welding an earth wire to the shroud and then running the back to the earthing bolt in the main unit. The fusing of the Neutral line has already been changed so that the Live line is now connected to the fuse.

As to why Chinese companies seem to use the same unit designators...well I think it is all designed to confuse ! If you see an 852 cheaper than another 852 and they look very similar, guess which one is likely to be sold  I count myself as a 'victim' of such tactics as I thought I was getting a unit like the KADA 852D+. My 852D+ works well but your original message did make me realise that all was likely not as it appeared !

[reflowman]

... My 852D+ works well but your original message did make me realise that all was likely not as it appeared !

After reading this excellent thread I just had to join this forum so I could chip in my two cents.

I have a 230V Kada 852D+. It worked well for about a year, albeit with very little actual on time. Then, when I wasn't watching, the air gun glowed cherry red (the smell caught my attention) but before I could hit the switch there was a loud bang and that was the end of things whilst I waited for a replacement element from HK.
To cut a long story short I discovered the following:

The reason for the overheat was a spuriously firing triac; said triac (BTA08 I think) was no doubt annoyed by  being driven in "bang-bang" mode by a non zero volt crossing optoisolator. (In the end I ripped out all the hot air circuitry and put my own design in.)

The air heater control circuit was driven from a zener at the end of a dropper chain from 230V. One dropper got so hot it had shed its cement coating. I suspect the design was just badly adapted from a 110V model.

There was no thermocouple failure or overheat protection.

The hot air element is not fused at all except at the wall plug.

As  in the WEP, the Kada is only fused in the neutral line - totally useless.

My Kada was also totally unearthed; reason: paint around the earth anchor and incorrect type of screw.

Whilst calibrating the thing after making the necessary repairs I discovered that the thermocouple op amp gain preset was cranked hard against the endstop (you just know it's a wrong-un when that happens) so it was impossible to get the right temperature at the air nozzle -very annoying as it was surprisingly accurate (give or take 10?) before it blew up.

When I first got the Kada my impression was that it was pretty good for the money but having lifted the lid it is very poor and unsafe by UK standards.  Shame really, given the same components it could have been designed in a much better and safer way.

I'm currently redesigning the whole thing with readouts that show actual iron and air temperatures (not just values from a dual-gang pot ) and a good sprinkling of protection circuits.

Quick plea for help: Anyone know the rated voltage/ current of the air pump in these things?  I see its got a few cement droppers between it and the triac but there are no markings on the case that I can see. They are sold on eBay as K03 pumps but I cannot find any info about them.


Bob

[saturation]

@aurora, thanks a ton for the review and photos.  Very helpful and vital.

Reflowman, thanks for those insights.  By chance do you have any photos of the damage, it would be good to append to your comments.

One thing this thread and that of the 858 show, is the tear down is actually mandatory to insure your own safety.  I do this mostly out of curiosity for China purchased units that are mains connected, but now its mandatory.

Sorry I can't help with the rating on the air pump.  Right now my only hot air source is a hot air gun.

FWIW I am not upset over the workmanship, as I expect it.  For some years I modify China devices rather than build from scratch.  At the very least the more costly items in projects are often non-electronic like knobs, casings, tubings etc., when finished a mod will be a lot better working and looking than if I did the whole thing completely myself, such as modifying a hot air gun, for example.

[mobbarley]

I have a working Kada if you need any measurements. First thing I did was open it up and upgrade the earthing / fusing - always planned to use it until it popped then just use its hardware and make my own controller with good parts.

[Alex]

Is this station CE marked?

[bilko]

It doesn't make any difference if it is. It does not prove that it complies with CE. If you want a CE sticker I can send you one, or you can get one from here

http://cgi.ebay.co.uk/100x-CE-Logo-Stickers-Labels-25mm-Permanent-Adhesive-/170653237228?pt=UK_BOI_Office_Office_Supplies_Stationery_ET&hash=item27bbb9bfec

[Alex]

I was going to say that the mains wiring does not meet the requirements for certification.

[bilko]

I would imagine that everything that is made in china is CE certified 

[Fraser]

I challenged the build safety of the unit with the UK supplier and was informed that all W.E.P hot air stations are tested and approved to the China 'Blue Dragon' safety standard, whatever that may be  Maybe I needed the 'Gold Dragon' standard The supplier is of the belief that the units they sell are totally safe to use in the UK.

[Alex]

More like fire-spitting dragon.

[mazy]

WEP or Yihua not good but good price Please look this link  www.hotair.pl

WEP 852d+ price 36 Euro 

[jery]

Hi, sorry for opening old thread, but can anyone share its new design of controller electronics for Yihua 852D+? Which should have real temperature displaying and other features?
Thank You

[-N-]

This came out of a Power +8000 110V  same as all the other duel led display 852D+.
 They were removed without care After the Triacs exploded (Again) took some traces with them.
 The other missing traces was just exhaustion on my part.
 
Maybe someone will design something better we can all build or it can be used for charred component .I.D.

Possibly  it will help someone.

-N-

[-N-]

Never seen a pic of the pump completely taken "apaaaaart " on the net  ,....
 So If you ever wondered whats inside the damm thing  heres your "Colored X- ray" Enjoy.   

[King_ZZ]

Hi I don't know if anyone can assist me.

The post is by someone else but i have the same issue... 853d-voltage-regulation-problems
Mine is stuck at 51.1v theirs is stuck at 35v 

Link to their post which i have commented on with my issue:
https://www.eevblog.com/forum/reviews/853d-voltage-regulation-problems/msg4357357/#msg4357357

Cheap and Chinese = recipe for a headache