newbie mistake wrong fuse

[alloby]

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.

[mariush]

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.

[alloby]

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.

[alloby]

top of main board

[alloby]

under main board near side is for air flow other side is for air suction

[alloby]

under main board

[alloby]

behind lcd display

[alloby]

station

[alloby]

I do have a multimeter and have a basic knowledge of capacitors resistors diodes

[alloby]

reverse of main board

[alloby]

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.

[kalel]

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.

[alloby]

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.

[kalel]

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

[ggkios]

On main board image, black spot on transformer. Magic smoke

?? ?? LG-D855 Tapatalk

[kalel]

On main board image, black spot on transformer. Magic smoke

?? ?? LG-D855 Tapatalk

Yes, I did not notice before, here:

[ggkios]

I woulsd start checking with this area, bridge rectifier and other components around it. Carefull with the big capacitor nearby

?? ?? LG-D855 Tapatalk

[alloby]

Thanks for that now I have somewhere to start I will update when I check

[Gyro]

On main board image, black spot on transformer. Magic smoke

?? ?? LG-D855 Tapatalk

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.

[ebastler]

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.

[alloby]

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.

[alloby]

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

[alloby]

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

[Gyro]

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.

[WaveyDipole]

I might be inclined to check whether that 47uF cap is shorted.