MAX850 Hot Air Station Repaired For Current Leakage
I was working on motherboard while removing some SMD component I got electric shock on my tweezer. What goes wrong? This happened two – three times.
I stopped work & got involved in diverted fault finding because some time it may causes more cost in any form of damage. I was working on Motherboard which was not connected in any power line & there is nothing on workbench around my working area, so what is the cause of electric shock. I am using MAX 850 Hot air Rework station for removing SMD Components.
While inspecting this unit I took line tester to trace the culprit & I found one.
So here I found current is coming out of metal nozzle of Hot air handle. Now I understand while desoldering the component this nozzle is accidently touches the tweezer which I was holding on other hand and I got electric shock.
Probable cause is earthing wire problem in the unit. So for further inspection I opened the Handle Unit.
I found only two wires for heating element inside the handle. There is no earthing wire.
I googled for some more information about these type of handle & element. I found different type of connectivity of the handle …. like some having 4 wires, some having 5 wires so on.
As this unit does not have auto cut off for Temperature of heating element. Hence it is having only two element wires. But what about Earthing. I opened the controller unit and it is having proper earthing on PCB but there is no earthing wire towards handle.
For further inspection I removed heating element from metal tube nozzle & I found some pieces of Glass fell down from the metal tube.
Now I come to know this glass is for what … This unit does not require earthing wire, because entire Metal tube is protected from the inside with Glass coating, so that element cannot touch in side metal part & it insulate the metal from the Coil touching on the body.
Because of broken glass on some place, heating element is touching the metal body of the tube & current is appearing on the body.
Now solution is to replace the entire handle unit because I doubt that only metal tube is available.
I am having some urgent work & I cannot wait till the part come. I just inspecting the handle unit clueless, and thinking for some other option so that I can carry on my work. While inspecting I found so many grooves in handle what is that for?
These Grooves are for Moving element back and forth so what I did I just moved the element little back side and inserted the metal tube on the heating element & Powered the unit & checked with line tester, now there is no current leakage.
I assembled back everything & tested again.
Now machine works perfect without current leakage.
This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.
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Note: You can check his previous repair articles on Laptop Making Ticking Noise
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Tayo
September 28, 2024 at 12:25 pm
Ingenious solution and good eye catching the position slots.
Would installing a silicone and rubber sheet/layer around the heating element work?
Yogesh Panchal
September 28, 2024 at 3:56 pm
Thanks! Tayo,
Good quality Heat resistant Silicon sheet may work because maximum temperature of this machine is 450°C but again it depends on thickness of the Silicon sheet, Because here Glass used thickness between 0.5mm & 1mm.,Rubber will not work & also it is toxic when burned.May be coating of some high temperature epoxy will work.
Parasuraman S
September 28, 2024 at 1:16 pm
Oh! What a strange case! I have never seen the inside of this blower, though I had one which I gave as a gift to a techie friend when a new one was bought. Good share. But where did the glass piece come from? And how did it break?
Yogesh Panchal
September 28, 2024 at 4:09 pm
Sir, this Glass coating is used as an electrical insulator inside the metal Pipe on which we replace nozzles.as i talked to service center they told me Glass can easily get broken if handle is banged,fall or collision.
Albert van Bemmelen
September 28, 2024 at 2:11 pm
Very strange and previously very dangerous situation you fixed! Because normally my Gordak 952A and other hot-air stations I know are always completely connected to the earth wire for safety on the nozzle metal outside. So without any glass and more than a only two wire cable inside.
Even the WEP898D repair I did in 2022 even had 8 wires to the hotair nozzle holder. See => https://jestineyong.com/replacing-bad-wep898d-heater-gun-smd-rework-station/
Waleed Rishmawi
September 28, 2024 at 4:22 pm
very interesting repair. I have not faced with such an issue. glad the machine is up and running for it is a very important device to have in the shop. thanks for sharing and have a blessed day
Yogesh Panchal
September 28, 2024 at 10:46 pm
Thanks!waleed
Yogesh Panchal
September 28, 2024 at 4:30 pm
Albert, Using this Hot-air station since last 15 years it was repaired once in year 2017, i already uploaded same article,This Hot-air station is entry level but it works good with good build quality.
https://jestineyong.com/how-to-repair-max-850-smd-rework-station/
Albert van Bemmelen
September 28, 2024 at 7:07 pm
Good that you already were able to fix the hotair station twice!
How soon something goes out of order no doubt also depends on how often it was used!
Mark J
September 29, 2024 at 3:21 am
Yogesh Happy to see you got it up and working again. Well done.
Yogesh Panchal
September 29, 2024 at 4:39 pm
Thanks! Mark J
Tito Kanshulu
September 29, 2024 at 10:27 pm
Very interesting and mind blowing kind of a repair. Thanks for sharing. We have learnt something new about these rework stations
Yogesh Panchal
September 30, 2024 at 10:15 pm
Thank You! Tito Kanshulu
Imoudu.O
September 30, 2024 at 4:55 am
Good job you hàve done with your hot air gun, i think mica sheet can be used to wrap the element,that was what i did when my hot air gun element coil got damaged sometime ago. Thanks for sharing.
Yogesh Panchal
September 30, 2024 at 10:29 pm
Imoudu.O,
Thanks! for your Tip.
Natarajan
October 15, 2024 at 9:46 pm
Sri Yogesh
Thanks for sharing a nice article. It is similar to the Water heater element
is getting shorted with the tank body. Generally water will penetrate in to
the element once the element stated to expand during heating. First few minutes
there will not be any shocking indication, Once the water started to become
warm we can realise it.
Awil
October 22, 2024 at 4:20 pm
thank you,this is very strange case,i didnot known that handle has glass protector.