EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: alloby on December 18, 2017, 02:06:42 pm
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Hi first I would like to say hello to everyone I am trying to learn more about electronics iphone repair in particular but have just made a big mistake that I hope I can rectify with help,right here we go I have a Jbc jt-2a hot air station it was working fine until last week when it stopped bowing air and then error 6 showed on display first thing in manual said was try new heater element wich I did but it was still the same I then had a look inside and found a fuse had blown but I replaced it with a t4amp 250v then when I turned station on and pressed start button I heard a small pop so I tested fuse and it was ok I then realised I had put wrong fuse in it should have been a T630L 250v.The reason I put the T4 250v in was because it said on back of unit fuse 4a 250v I did take note of the original fuse but thought thats why it blew because it was too low a rating so my question is what is likely to blow in these circumstances or how do I troubleshoot hope some one can help thanks in advance.Also unit still powers up but still same error.
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Your original fuse was a time delay fuse for 650mA (0.65A).
You inserted a fuse designed to blow at 4A and it blew up.
This means something inside is shorted or using so much power that it blew up even the 4A fuse, by letting more than 4A of current go through for enough time to blow the fuse. If you had inserted the proper fuse, it would have blown anyway.
Something made these fuses blow, you have to find what's shorted or what's using too much power and replace that something before you put a new fuse in place, otherwise you'll continue to break fuses.
Open the device and follow the traces from the fuse and see what components you have and try to determine if they're broken or not. Visually check if you see some chip blown up or with signs of failure (cracked chip, something with smoke residue and so on ) then maybe if you have a digital multimeter put it in continuity mode and test various components (but you have to know how to test those and I suspect you don't know how)
If you can, take some pictures of the circuit board inside and maybe we can suggest what to check and how to check various components in the picture or maybe there's some common fault and people can tell you exactly what to replace on the circuit board to get your station working.
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Hi thanks for reply I will take some pics and post, one thing to note the original fuse was aT630L 250V and when I put the 4A 250v in that has not blown I heard a small pop but 4a fuse was ok so obviously something else has gone.
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top of main board
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under main board near side is for air flow other side is for air suction
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under main board
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behind lcd display
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station
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I do have a multimeter and have a basic knowledge of capacitors resistors diodes
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reverse of main board
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I am going to start trouble shooting but I was wandering if by using a larger fuse wich did not blow but I hearing small pop if any one has any thoughts on what is likely to have blown.
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I am going to start trouble shooting but I was wandering if by using a larger fuse wich did not blow but I hearing small pop if any one has any thoughts on what is likely to have blown.
I don't know anything about the construction of such circuits (a newbie here) but if you check all components visually, is there anything a bit strange looking? Perhaps some black charring on the board near a component? How about the capacitors, are they all intact?
One "random" way to is to desolder many components - for TH (at least one leg) and test them, but of course there are experts here that might know what components are more likely to fail than others.
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Hi thanks for reply to be honest there are a few components on board I am unsure what they are so to even test them is impossible for now ,I am trying to research them.
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Hi thanks for reply to be honest there are a few components on board I am unsure what they are so to even test them is impossible for now ,I am trying to research them.
Can you take a close up photo of those components (and/or mark them somehow)? Maybe you could get some help here
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On main board image, black spot on transformer. Magic smoke
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On main board image, black spot on transformer. Magic smoke
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Yes, I did not notice before, here:
(https://i.imgur.com/FpEWXi0.jpg)
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I woulsd start checking with this area, bridge rectifier and other components around it. Carefull with the big capacitor nearby
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Thanks for that now I have somewhere to start I will update when I check
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On main board image, black spot on transformer. Magic smoke
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Well spotted! ... and welcome to the forum :)
I suspect that it's actually the resistor next to the transformer - it looks to have white stripes further along. Something else caused that to blow if so.
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The reason I put the T4 250v in was because it said on back of unit fuse 4a 250v.
I did take note of the original fuse but thought thats why it blew because it was too low a rating
First, good luck in fixing the problem with your solder station! With a bit of luck, the failed resistor is the root cause of the problem. But, as others have pointed out, it may also be some other component failure in this area of the circuit, which has taken first the fuse and then the resistor down.
Second, please don't forget the general learning lesson from this. If a fuse blows -- especially if that happens spontaneously, after the device had been working correctly for a while -- there is probably an underlying reason. It's OK to try again after replacing the fuse; they sometimes do die at random (but rarely). But DON'T put in a fuse with a much higher current rating! You are bound to experience just what you did: The fuse now stays intact, but can no longer protect the downstream circuit.
For your solder station, the 4A rating apparently refers to the *input* fuse. That fuse seems to be located just below the power jack in the back (behind a little lid which is accessible from the outside). The internal fuse was probably populated with the correct value. It would have been nice of JBC to also print that value in the silkscreen, which I can't spot in the photograph.
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Thank you for your help and advice I have spoken to someone online who has same model they have confirmed the correct fuse as T630L 250V as we thought and as soon as I make my checks I will update, though I am still a little unsure I can check resistors etc but no clue about transformers.
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The resistor is a 6.8ohms and it reads OL the writing on it is RB61 6?8 AN it looks like it has blown so that confirms it
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The bridge rectifier reads red probe on + black probe on 1st ~ =OL
red probe on 1st ~ black probe on + =0.0550
red probe on 1st ~ black probe on 2nd ~ =0.0546
red probe on 2nd ~ black probe on first ~ =OL
red probe on - black probe on 2nd ~ = 0.543
black probe on - red probe on 2nd ~ =OL
red probe on 1st ~ black probe on - = beep or 0.001
black probe on - red probe on 2nd ~ = beep or 0.001
red probe on + black probe on 2nd ~ =OL
black probe on + red probe on 2nd ~ = 0.547 I think that means its faulty can anyone confirm or how to test a better way thanks in advance
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Well done on the tracing. Yes, a zero ohm reading between any two pins on a bridge rectifier means that at least one of the internal diodes has shorted. That would be enough to blow the resistor if it is in series. :-+
P.S. Datasheets for both the RB61 6.8 Ohm resistor (5-7W wirewound) and the bridge rectifier part numbers show up on an web search so you hopefully shouldn't have any difficulty sourcing replacements.
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I might be inclined to check whether that 47uF cap is shorted.
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Thanks I will check that cap tomorrow and let you know is it best to check out of circuit .
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Check it in circuit first. You may see your multimeter numbers climbing up as the capacitor charges if everything is good. There are very few (no?) cases where a capacitor is shunted by a low value resistance.
If you do get a very low resistance then think about taking it out, but I would suspect the load that this capacitor is smoothing the output of the bridge rectifier for rather than the capacitor itself.
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I need to read up how to check it properly also can anyone tell me if a rwm 6x 22 RB57 will be ok instead of rwm 4x22 RB61 I am having trouble finding a RB61 but RS stock RB57 thanks in advance.
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I checked the capacitor its a 47micro farad 400v and off the board it reads 52.6 micro farads and it charges up and discharges so I assume it is ok.I also reversed my leads and still read 52.6 micro farads.
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I have just doubled checked bridge rectifier and I had a measurement wrong
The bridge rectifier reads red probe on + black probe on 1st ~ =OL
red probe on 1st ~ black probe on + =0.0550
red probe on 1st ~ black probe on 2nd ~ =0.0546
red probe on 2nd ~ black probe on first ~ =OL
red probe on - black probe on 2nd ~ = 0.543
black probe on - red probe on 2nd ~ =OL
red probe on 1st ~ black probe on - = beep or 0.001 and black probe on 1st ~ red probe on - =beep
black probe on - red probe on 2nd ~ = 0.0543 this is now correct
red probe on + black probe on 2nd ~ =OL
black probe on + red probe on 2nd ~ = 0.547
I entered it wrong first time so can anyone confirm it is still faulty
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I would say that one internal diode is shorted. So it is faulty
I don’t have very much experience with this so someone may say different.
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Thanks I hope so I have double checked and that was the only one I had wrong
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Yes, the rectifier is faulty. I was trying to ascertain whether it had become stressed by a short across the smoothing cap. Sounds like the cap is Ok so there must be another explanation for the rectifier failure.
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Occasionally rectifiers just fail, I wouldn't spend much time looking for the fault. Especially in low cost Chinese gear it was probably spec'd for the lowest cost possible and may have been of questionable quality to begin with.
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Occasionally rectifiers just fail, I wouldn't spend much time looking for the fault. Especially in low cost Chinese gear it was probably spec'd for the lowest cost possible and may have been of questionable quality to begin with.
Hes got a jbc, starting price for one is around 500$, but yeah i sometimes bridge rectifiers fail
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I have ordered the exact bridge rectifier part but I cant find exact resistor rwx422 rb61 6.8ohm 7w so I have ordered Vishay RWM 6x22 rb57 Series Axial Wirewound Resistor 6.8? ±5% 7W ±75ppm/°c I am thinking they will be ok so if anyone thinks they are not suitable let me know
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I have received new bridge rectifiers and after testing it confirms my one was faulty I am just waiting for resistors and will update when they arrive.
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I got my resistors in post and soldered it on board along with bridge rectifier put new fuse in and it works,I cant believe it so thanks to everyone who helped, to some it might have been an easy fix but to me I felt I was out of my depth but now I have more confidence in myself and it has helped me to think about what is happening in a circuit I feel I have learnt a lot and this forum is the reason why so again a big thank you and hope everyone has a prosperous new year.
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Glad it worked, hopefully it will stay this way
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Congratulations on the successful repair alloby. Best wishes for the New Year.
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Congratulations and Happy New Year
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Hi everybody !
I would like the JBC JT-2A service manual, or schematics, or circuit diagram.
Do you have it ?
Thank you for your help!
Best Regards,
Gabor
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Hi , i have a question...
What is the type number of the IC on the picture ( in the red circle )
Thank you for your help.
Best Regards,
Gabor
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Sorry to bump an old thread, but i had the exact same issue.
Seems like the bridge rectifier for the air is a common failure mode on these. Did not find this thread when searching for some reason, might have saved me the 250 USD i paid for a new heating element hoping that would solve the issue.
The unit i have is a JBC JT-2A hot air station.
The bridge rectifier in question is a DIOTEC B500C1500B. It has a bit unusual pinout so i have not been able to find a substitute (~+~-) Edit: Vishay VS-2KBB100 seem to be equivalent. Have ordered one as it is easier for me to get hold of than the DIOTEC B500C1500B.
Hopefully this will help somebody else having similar issues :)
PS: gaborgabor: The IC you are looking for is a Vishay BRT23M optocoupler. Seems like it is obsolete and out of production, but i am sure that there are some similar triac optocouplers with similar specs and package type available if you spend some time comparing the datasheet with filters on mouser/digikey/farnell/or others.
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Just going to throw in a comment as well for future searchers. We had a power surge that blew a bit of various equipment. The Bridge rectifier was indeed the part that failed on our JT-2A as well. I just bodged in a normal pinout bridge rectifier but just twisted the legs and expoxied them to keep em apart heh.