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Circuit Board
- Thread starter dazling
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At the bottom of the picture, the round disc with burnt legs is a ceramic capacitor. There should be a code printed on it.
They look like the remains of surface mount resistors. Nothing to be lost by unsoldering, should at least find out how many terminals, give some clue.
Comments above are all valid as well, and it's a double sided PCB. If there's damage to the other side as well, it's pretty hopeless.
I wouldn't say for definite that the disc component to the bottom is a capacitor, it maybe a varistor of some kind but I don't know how automotive circuits are usually protected. It looks a bit big for a ceramic disc and there are already electrolytic and poly (red box) capacitors there, no-one has used ceramic disc capacitors for IC filter caps for years surely 
.
The thing next to the connector might be an inductor or possibly a diode for polarity protection. A quick guess would be that the disc component is across the supply, has gone short and has cooked the inductor or diode.
Use an Ohm meter and read the value across the disc component @dazling.
The circuit will probably work without these by removing the disc and bridging the other component but they are there for a reason and something caused it. Metal oxide varistors fail after repetative operation (they clip voltage spikes off the supply).
Edit:
Just read it was caused by jumpstarting with lights on.
Seems there is another component near the frazzled one, it looks like a polarity band on the left. The frazzled one would possibly be the same component.
.The thing next to the connector might be an inductor or possibly a diode for polarity protection. A quick guess would be that the disc component is across the supply, has gone short and has cooked the inductor or diode.
Use an Ohm meter and read the value across the disc component @dazling.
The circuit will probably work without these by removing the disc and bridging the other component but they are there for a reason and something caused it. Metal oxide varistors fail after repetative operation (they clip voltage spikes off the supply).
Edit:
Just read it was caused by jumpstarting with lights on.
Seems there is another component near the frazzled one, it looks like a polarity band on the left. The frazzled one would possibly be the same component.
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the little component is frazzled lol and it is only connected on the right hand side now as we look at the pic it has started to lift the track aswell
I will take it apart and see if it is double sided apparently it is 3 grand for a new 1 my mate does bullshit a little but I know a second hand 1 is £800
was hoping to sort this mainly just as a challenge and to save him a few quid lol
will report back on weather its double sided or not
I will take it apart and see if it is double sided apparently it is 3 grand for a new 1 my mate does bullshit a little but I know a second hand 1 is £800
was hoping to sort this mainly just as a challenge and to save him a few quid lol
will report back on weather its double sided or not
That sort of price makes a big difference! If you find out how many connections each "burnt thing" has, as Spectre says, there is hope, even for a double sided PCB.
But if it's a multi-layered PCB (shouldn't think so, can't see space being an issue), may as well start saving.
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it looks like just a flat bar so only 1 connection each end will try to find a stronger magnifying glass for a better look
You need to get it/them off anyway, main thing is try not to damage the board any further. Could even be ident on pcb or component underneath. Good Luck!
Just remembered what HappyH spotted in post #3. Is that a crack in the IC, or just a scratch ? If it's a crack, very doubtful about repair.
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Measure the disc resistance, on phone so hard to elaborate. Frazzled thing had 2 leads.
What's the red gunk all over the PCB?
That's had some serious power go through it. I suspect the damaged components are not just the obvious ones you can see
Can you get schematics for the PCB?
That's had some serious power go through it. I suspect the damaged components are not just the obvious ones you can see
Can you get schematics for the PCB?
The red gunk is protective lacquer. I've had a quick look for a schematic, many seem to be just wiring diagrams.
@dazling....can you get the tractor model number, would help with a schematic search?
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there is no crack in the IC was just a greasy mark
its from a Ford New Holland 1998 8340 tractor
the only identifying marks on the board is a barcode sticker with as follows printed on it
DIC
501017700000
3483 20/04/98
I have done a quick search to try and find more details but have not been able to find anything yet
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Spectre is probably right that it is a varistor, if so then the frazzled component would need to be a weak link as in an smd fuse or diode.
Normally I would say a fuse but as its' for a tractor??
The left leg of the suspected varistor is connected to ground, desolder the other leg and if you measure low resistance then the component is u/s. If it measures high then I would resolder and then try something like a 3.15AT fuse with my meter in series to measure the current. Based on the current reading I would fit the nearest appropriate fuse.
Sounds a bit of a bodge but these manufacturers do this on purpose. They remove id's from components and never release circuit diagrams so they can charge extortionate prices.
Normally I would say a fuse but as its' for a tractor??
The left leg of the suspected varistor is connected to ground, desolder the other leg and if you measure low resistance then the component is u/s. If it measures high then I would resolder and then try something like a 3.15AT fuse with my meter in series to measure the current. Based on the current reading I would fit the nearest appropriate fuse.
Sounds a bit of a bodge but these manufacturers do this on purpose. They remove id's from components and never release circuit diagrams so they can charge extortionate prices.
and that is the reason they have covered it in the red resin as they do not want you working on it?
Sounds like a practical course, just 2 pins does narrow down the options for the "frazzler".
If it was a fuse though, would all that damage happen before it "blew"? A diode breakdown maybe?
@dazling.....Sorry, can't find a cct diagram even with the model info, not too surprising now I see photo's of complete board.
Suggest you follow above, connecting temp fly leads on "frazzler" ends (one end looks like a connector pin, anyway).
That way you can experiment without being bothered with component size, type etc. and minimise risk of further pcb damage
until final replacement of whatever works.
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Quite probable Danforth,the vdr would start to go low resistance when its' voltage rating is exceeded. This causes a virtual short to ground to minimise damage to more sensitive components.
The resulting short then would draw more current exceeding the limits of the fuse, same effect with a diode but far slower. I can't understand why jumpstarting caused the burnup either as the parallel connection still only equals the input voltage, the current being drawn dictated by the circuit until the vdr went low.
I have seen far worse damage with a vdr/fuse combination where both have been obliterated but these were due to lightning strikes
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