Hakko 850 Hot Air Rework Station

[Adler]

I found this place near my house that recycles old electronics on ebay. I was picking up a range extender for my home network when I saw this thing on a shelf. Asked the guy about it, he said, "Doesn't power on", I said, "Here's 10 bucks, let me take that off your hands".





First think I did was try it out and the first thing I noticed was that it very much so DOES power on. As soon as the plug is inserted the pump starts working on max, the switch is off. When I turn the switch on, the pump responds to the dial as expected. No heat.

Opened it up and its pretty clean inside, no obvious issues.











When I opened the hand piece I found the issue pretty immediately....





Yeah... We're not going to get much heat with that thing... I believe the loose wire is to ground the metal tip.

Interesting that there doesn't seem to be any temperature sensor in the hand unit.

I suspect that it is detecting that it needs to go into cool down mode when its initiallyplugged in, because the element is missing. Does that make any sense?

Anyways, it looks like I need to source a new element. Anyone know the cheapest place?

[Adler]

Do you guys think this is the element I'm looking for?

eBay auction: #270668275288

That one is 250w and I see available 750w units.

[Neganur]

http://shop.wiltec.info/product_info.php/language/EN/info/p2907_AOYUE-Originalersatzteil-Hei-luftheizelement-mit-CPU-Aoyue-Type-10094.html

there seems to be a Hakko model 850c too:

http://shop.wiltec.info/product_info.php/language/EN/info/p2908_AOYUE-Originalersatzteil-Hei-luftheizelement-Hei-luft-Aoyue-Type-10093.html

btw, check that black wire, it should have a connector in the middle which you can separate: (ignore the red circle, and yes this handpiece is from an Aoyue 968)

[Neganur]

Do you guys think this is the element I'm looking for?

eBay auction: #270668275288

That one is 250w and I see available 750w units.

It looks very similar. The heating element has a thermo-couple at the tip btw.

EDIT: noticed the 110V, not sure what the ones from the German shop are rated for but at least they should look similar.

maybe this helps, there is a nice picture of the hand piece on page 12
http://cn.100y.com.tw/pdf_file/HAKKO-850B.pdf

[Fraser]

There are different versions of heater used in the various copies of the Hakko 850. Some use a 2 wire plus safety earth, whilst others use a 4 wire plus safety earth. You just need to buy a 850 heater that is the right number of connections and you will be fine. A VERY IMPORTANT NOTE: The metal heat tube should be earthed AND should contain a Mylar insulating sleeve to stop the heater shorting to the metal. For a few dollars you can buy a new heater and some come with a new Mylar insultion sleeve. For a few dollars more you can buy a complete handle assembly. That is the route I took and its plug & play 

Yours appears to be a 2 wire plus earth model.

Take a look here:

http://www.ebay.co.uk/itm/Hot-air-Gun-Rework-Station-handle-for-SMD-Diapraghm-rework-station-2-wires-AUS-/360396531453?pt=AU_B_I_Electrical_Test_Equipment&hash=item53e94ea6fd


If you are in the USA you will need to track down a seller of the 110V version of course.


Fraser

[Adler]

btw, check that black wire, it should have a connector in the middle which you can separate: (ignore the red circle, and yes this handpiece is from an Aoyue 968)

Yup, the black wire has a connection in it. Can I just solder it back onto where it goes or will that part get so hot that the solder melts?

It looks very similar. The heating element has a thermo-couple at the tip btw.

How does the thermocouple communicate with the control part? there are only 2 wires which I assume are power for the element.

There are different versions of heater used in the various copies of the Hakko 850. Some use a 2 wire plus safety earth, whilst others use a 4 wire plus safety earth. You just need to buy a 850 heater that is the right number of connections and you will be fine. A VERY IMPORTANT NOTE: The metal heat tube should be earthed AND should contain a Mylar insulating sleeve to stop the heater shorting to the metal. For a few dollars you can buy a new heater and some come with a new Mylar insultion sleeve. For a few dollars more you can buy a complete handle assembly. That is the route I took and its plug & play 

Yours appears to be a 2 wire plus earth model.

Take a look here:

http://www.ebay.co.uk/itm/Hot-air-Gun-Rework-Station-handle-for-SMD-Diapraghm-rework-station-2-wires-AUS-/360396531453?pt=AU_B_I_Electrical_Test_Equipment&hash=item53e94ea6fd


If you are in the USA you will need to track down a seller of the 110V version of course.


Fraser

Are you sure there is a mylar sleeve? It doesn't show up in any parts diagrams that I have found.

I think Ill try to track down the Chinese manufacturer of these parts. That will probably be my cheapest option.
Do you think I can get the 4 wire element and just leave 2 wires dangling?

[Fraser]

Yes it definitely needs an insulator but that is normally part of the air pipe so may not be shown as a separate item ?

I am uncertain whether the two wire units have any true temperature feedback as there is no thermocouple at the tip as is the case with the 4 wire version. It may (?) just adjust the current through the element against a calibrated scale. In other words its like those cheap soldering irons that are controlled with what is effectively a dimmer circuit. I can't help you on this with facts as I have not investigated the 2 wire control system. I note that the 2 wire element often has a 'lump' attached to the element shaft. This may be some part of a temperature control loop but I cannot be certain. I do not think you can use a 4 wire element in a 2 wire handpiece.

Take a look at the attached schematic for a 988 model of hot air station. It would be worth tracing out your heater control circuit to see how it works in your unit.

Sorry I cannot be of more help. I will look at my spare elements (2 and 4 wire types) to see if anythong useful to you can be discovered.

Update. I just had a look at my spares holding. Sadly all my heaters are 4 wire types, with a thermocouple, so I cannot provide any information on the 2 wire type.

Regards

Fraser

[Fraser]

OK,

I found some Hakko 850B schematics in my archive. May be of some use to you ?

I am wondering whether on the '2 wire' heater the 'lump' on the shaft is an overheat cut-out like those found on hair dryers. It looks like such a thermal protection device and would be of the bi-metallic self-resetting type, hence the size. The lack of a temperature control loop could be considered an overheat risk requiring such a safety device ? (but then a 4 wire without such a device can overheat if the control loop fails  )

Kind Regards

Fraser

[Adler]

I finally got my new element in the mail today.

Plugged it in with my hopes high and...... nothing... no heat whatsoever.

I opened the handle and checked the voltage at the element and found nearly nothing (though something).

So I cracked it open once more.

Couldnt find anything obviously wrong with it so this time, I pulled the board off.



Nothing obviously wrong...

flipped it over...



Well thats weird... lets have a closer look.



I have no idea how this happened but maybe one of you can help.

I patched it up and put it back together.




aaaand... it works... or, it did. it worked for about 2 minutes and then stopped producing heat, I need to investigate why.

[Fraser]

Whatever was connected to that "-" pin between the two vaporised PCB tracks is delivering a massive current through it to the 0V rail. A catastrophic failure of a component is likely.

When you see PCB tracks vaporised like this you should not apply power again until you discover what caused the excess current flow. Doing so just risks further damage. Without the schematic and the PCB in front of me, I am not able to be certain of the failure. Trace the "-" connection back through the cable that connects to it. Then trace the route that the current has taken from the source. I suspect you will find a shorted Triac.

My fiirst check would be Triac "TH1" I think you will find it to be short circuit anode to cathode.

Regards

Fraser

[Adler]

Whatever was connected to that "-" pin between the two vaporised PCB tracks is delivering a massive current through it to the 0V rail. A catastrophic failure of a component is likely.

When you see PCB tracks vaporised like this you should not apply power again until you discover what caused the excess current flow. Doing so just risks further damage. Without the schematic and the PCB in front of me, I am not able to be certain of the failure. Trace the "-" connection back through the cable that connects to it. Then trace the route that the current has taken from the source. I suspect you will find a shorted Triac.

Regards

Fraser

That pin is connected to an LED. The LED is fine, still works.

[Fraser]

Ok.

Please check TH1 (with the silver heatsink).

I believe that what you have is the mains supply being fed to the heater element via the Triac TH1. The Triac has failed and gone short circuit so instead of a pulsed, and so controlled, mains feed to the heater, there is now a continuous power feed that has likely caused catastophic failure (shorting) of the heater and overloaded the PCB track in the return path.

From your pictures it is evident that TH1 has failed in the past and has been replaced. Any similar Triac will replace it. I would use a BT137-800. It is rated at 8A 800V. This gives 200V headroom over the original 600V part, and the same current rating.

The bad news is that you have likely burnt out your new heater element during your 'test'.

Fraser

[Adler]

Ok.

Please check TH1 (with the silver heatsink).

I believe that what you have is the mains supply being fed to the heater element via the Triac TH1. The Triac has failed and gone short circuit so instead of a pulsed, and so controlled, mains feed to the heater, there is now a continuous power feed that has likely caused catastophic failure (shorting) of the heater and overloaded the PCB track in the return path.

From your pictures it is evident that TH1 has failed in the past and has been replaced. Any similar Triac will replace it. I would use a BT137-800. It is rated at 8A 800V. This gives 200V headroom over the original 600V part, and the same current rating.

The bad news is that you have likely burnt out your new heater element during your 'test'.

Fraser

Seems reasonable. I better check this out.

I'm not too positive how to check a triac but here are my readings from each of the leads.

T1-T2 = infinite
T1-Gate = 174ohms
T2-Gate = infinite
T1-heatsink = infinite
T2-heatsink = 0ohms

If there is any other simple measurement I should be doing, please tell me.

I should also mention that the station appears to work at this point.

[Fraser]

Hmmm, thats interesting. I would have expected to see T1 to T2 reading short circuit and close to 0 Ohms. That Triac appears to be OK. There remains the possibility that the circuit that drives it is no longer applying a pulse train to its gate, but rather a coninuous 'on' signal. The TRIAC is rated at 8A so its able to put up with some abuse. To blow those PCB tracks I would have expected the required current to be greater than the TRIACs survival current and it should have beed destroyed ?

This is still a bit of a mystery I am affraid. I can usually work out a failure cause when a PCB is in front of me but this is a bit harder via messages 

If you want more help could you take good decent resolution pictures of the top and bottom of the PCB and add a conmment or sketch of the pcb cable connections.

I have an 850 myself but it is branded Duratool so is liekly a clone and not much help. We do have an 850B schematic though so it may haelp solve the riddle.

You did fit a mica insulator inside the air tube didn't you ?

Also, please check that the heater is still OK after your test.

Fraser

[Adler]

If you want more help could you take good decent resolution pictures of the top and bottom of the PCB and add a conmment or sketch of the pcb cable connections.

I will attempt to photoshop the 2 sides of the board together to make a circuit diagram.

You did fit a mica insulator inside the air tube didn't you ?

There is an insulator in the metal tube, it was always there but I hadn't noticed it before.

I have a theory though. When the heater is in the metal tube the tip touches the front of the tube.





Wouldn't this cause a short to ground? So far, I have not grounded the metal tube as it is supposed to be.

[Fraser]

That is REALLY dangerous 

The tip is 'live' and must not touch the air tube. It should sit about 1/4" away from the perforated 'grille'.

If the tube is not earthed yet, no harm will come to the element but you risk electrocution if you touch the metal tube !

Fraser

[Adler]

Well... Im glad I looked into this...

My guess is that the previous owner used a similar element and it shorted to ground vaporizing those traces.

No doubt I could also damage whatever I work on by touching the tip to it.

I'll look into ways to secure the element lower down.

[KG7AMV]

Like this post...

[mclareniak]

Please do not have the wiring diagram for HQ850? PCB is written DUOLI850.

well thank you