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
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.