Electronics Help with damaged PCB

Hi All

I've got a problem with a PCB and I need some advice, I don't know if here would be a good place to post as it's not really computer related (but you guys were the only place I could find).

Basically I've never seen anything this bad but I wondered if this was reparable?

http://oi52.tinypic.com/258ym9z.jpg

Please let me know if you know of any forums where I could get some advice on this.

Thanks

 

We don't have a specific forum for it anymore, but we do have a tag in the modding section (moved and tagged appropriately).

 

Nasty, any idea what caused it- it doesnt seem to be related to the components around it, looks more like either something on the reverse of the pcb or something contacting the board and causing a short somehow...

 

Thanks for the reply, this is a picture of the temporary replacement we've borrowed...

http://i54.tinypic.com/15ogeix.jpg

It looks like that silver dot which has a trace from the left hand side of the fuse to the unit marked k2 has caught light. It's in a very dusty environment which is perfect for arcing apparently.

It's going to cost £700 to replace this board so if we can fix then I'll give it a go.

Just about to take K2 off and see what is it

 

Scratch off the green paint where I've marked with orange.
Solder wires where I've marked with blue.

 

I would check continuity first, before scratching off solder resist (paint he he nice one).

odd thing is i like the way the fuses all seem to be ok, with a circuit drawing i could prob repair, but not in electronics trade as such anymore.

Yep ya typical replace board at stupid prices now, what happened to the true repair technicians these days, seem to of been replaced with the IT type boys, oh ive replaced board and it now works, oh will be £700 instead of a £50 repair cost.

Oh well.

 

Interesting damage

It looks very similar to some damage i've seen on pcbs where a bug has crawled along and shorted out a couple of contacts. In the few cases i've seen, poor mr bug who thought he was so lucky to find a nice warm corner to set up camp, was suddenly incinerated without a trace

Repairing the tracks with wire as shown above would be fine It is possible, that when mr bug or whatever the hell burnt, he may have also overloaded other components further down the trace... now it does look like only the lower trace may have been damaged, and if so then chances are all the components on the pcb would probably be fine... but if he shorted out two or more of those traces, then he might have taken out some other parts

I'd give the pcb a clean first, and hopefully it's only the lower track which is damaged.

 

Thanks for the replies.

I'm making enquiries about getting this fixed, it's worth £50 to me to get it done properly.

This is for an industrial jigsaw and the PCB is basically a switching box, aside from the bug thought what else could have caused the damage? Eg: If the saw motor seized could that have caused a surge? Bear in mind it's a very dusy environment so is arching a possibility?

Thanks again for all the input so far

 

I think it was arcing, there are smoke trails moving up from the fuse to the relays.

 

Was this pcb covered in dust?

If so, then the dust can absorb moisture in the air, especially after a cold night, and could easily have provided a path for a short/arc like this to occur.

And of course, with these circumstances, there is a high chance of damaged components on the pcb.

 

Instead of scraping off the solder resist, you might want to track it to the nearest soldered joint and solder the wires onto there. In my experience, the tracks tend to part with the board very easily when you try to solder to them.


Bigger


Those K1,2,3 etc are relays.
Send it to me and i'll do it for you, if you want.

 

Thanks for the help, have sent it off today to Greasleys who are gonna do a simple wire bridging repair.

Yes, it's an extremely dusty environment (wood saw) although the board was pretty clean. And there have been some pretty cold nights.

The only thing I'm concerned about now is putting a band aid on the symptom without understanding the cause.

The replacement board we've borrowed doesn't work (switches trigger, leds light up but there's a high pitched whine coming from around the saw motor area, the motor itself isn't seized) and the only info I have is that it 'wasn't right' from the people who have lent it to us. This wouldn't be a concern apart from the fact the saw worked for a couple of days after we put the borrowed pcb in, then stopped.

So only thing to do is wait I guess, get the repaired one back in, see if it works and if not take from there.

Thanks again for the input, only just realized how dangerous electronics are in that kind of environment (mind you it's been ok for 15 years *touches wood*)

I'll keep you posted

 

If the PCM was fairly clean, then I doubt a light coating of dust could do this.
I'm guessing a bug or other foreign object such as a screw or bolt did this, as if a motor was overloaded, then a fuse would have blown.

Did you clean then check the continuity and condition of the tracks?
Because it looks to me that those thin long tracks might all be fine, but i dunno what is supposed to be at ground zero just above that fuse?

Is there supposed to be a component there, such as a diode or resistor?
You can compare the board to the other one.

 

I'd like to see what's on the other side of the board. Looks more like a trace or three on the inside of the board cooked off, and not the ones on top.

 

just to let everyone know all is fine with the repair. Thanks again for all the advice and help.

I guess the cause will remain a mystery!

FWIW there is a pic of the replacement board above mva it was kind of a junction node thing where the trace went from the fron to the back of the PCB.

Everything's working for now, hope it stays that way!

Cheers!