Repair of cooker hood PCB trace

[Wombatdoc]

Hi. I’m wanting to repair the pcb on my cooker hood. I’ve attached a picture. My issue is that the tracts are a lot wider (around 5mm) than the jumper wire I was planning on using and I wasn’t sure if I should be using a lower gauge wire; I’ve was planning on using enamelled copper wire AWG ~29. Any advice would be much appreciated.

Cheers

Rich

 

[winston1]

AWG is American wire gauge. Not available over here. We use SWG standard wire gauge which is different.
To answer your question the wire you have looks OK. PCB tracks don’t normally carry much current.

 

[Wombatdoc]

For some reason, I thought this was an American site so converted wire (0.27mm) to nearest AWG.

Thanks for such a quick reply

 

[SUNRAY]

For a start AWG size wire is freely available in UK, despite being an American standard, 29AWG will be rated somewhere in the region of ½amp so should handle about 100W with ease.

 

[Wombatdoc]

Cooker hood is rated 190W, so I figure I’d need something capable of carrying about 0.9A? (Or is my reasoning fundamentally flawed here; as you can tell, my understanding of electricity is extremely basic; I’m presuming that it will be 0.9A flowing through the PCB?) May be 0.4 or 0.5mm to be safe?

 

[SUNRAY]

Cooker hood is rated 190W, so I figure I’d need something capable of carrying about 0.9A? (Or is my reasoning fundamentally flawed here; as you can tell, my understanding of electricity is extremely basic; I’m presuming that it will be 0.9A flowing through the PCB?) May be 0.4 or 0.5mm to be safe?

If you have some of that size then ideally yes, or use 2 or 3 strands of the 29AWG to be sure. Alternatively use a piece of 0.5 or 0.75mm² flex like the piece already in there.

 

[EFLImpudence]

For some reason, I thought this was an American site so converted wire (0.27mm) to nearest AWG.

That is the diameter.

We use the cross-sectional-area as the 'size'.

0.27mm. diameter is 0.064 square millimetres c.s.a.

 

[ericmark]

I looked at title and thought of the discworld series and particular crunchy bits (PCB's) which was clearly taking the Mick out of Polychlorinated biphenyls a banned substance also known as PCB's I had never thought of printed circuit board.

But I would use what ever cable was to hand, at 190 watt it is not high current.

 

[Harry Bloomfield]

I looked at title and thought of the discworld series and particular crunchy bits (PCB's) which was clearly taking the Mick out of Polychlorinated biphenyls a banned substance also known as PCB's I had never thought of printed circuit board.

But I would use what ever cable was to hand, at 190 watt it is not high current.

I agree, but I would something more rigid and able to stay put. Rather than enamelled wire, which there is no need for, I would use a bit of earth wire from a bit of 1.5mm twin and earth, match the original route and tinning it on that bend so there is no chance of movement.

 

[bernardgreen]

Harry's advice is good

 

[Robin0577]

I agree, but I would something more rigid and able to stay put. Rather than enamelled wire, which there is no need for, I would use a bit of earth wire from a bit of 1.5mm twin and earth, match the original route and tinning it on that bend so there is no chance of movement.

Harry's advice is good

Yes, agreed.

Then, if possible, coat the repair with something non conductive. Conformal coating or transformer varnish would be ideal, but pretty much any varnish would probably do the job. (even nail varnish, provided it doesn't contain any metallic sparkly bits)

 

[flameport]

PCB traces are very thin, and even if those ones are what American types call 2oz copper, that's only 70μm, so a 5mm width is about 0.35mm²
Plenty of PCBs are only 1oz or even less.

 

[BS3036]

PCB traces are very thin, and even if those ones are what American types call 2oz copper, that's only 70μm, so a 5mm width is about 0.35mm²
Plenty of PCBs are only 1oz or even less.

True, but bear in mind they have a large surface area to dissipate the heat and so can carry more current than you might expect. There are calculators on-line to show what they can do.

 

[JohnW2]

PCB traces are very thin, and even if those ones are what American types call 2oz copper, that's only 70μm, so a 5mm width is about 0.35mm²

That's true, and interesting, since it surprises me (since I've never thought to do the sums).

As you say, PCB tracks are extremely thin. As a result, I would not intuitively have thought that, even with "2oz copper", the CSA of a 5mm wide track would be anything like as high as 0.35mm². I find it even more counter-intuitive when I realise that it means that a track just over 14mm wide would have a CSA of 1 mm² (a size of circular cross-section conductor we can also visualise).

So, realisation of these figures almost 'reassures' me about some of the PCB tracks I see!

Kind Regards, John

 

[mattylad]

PCB traces are very thin, and even if those ones are what American types call 2oz copper, that's only 70μm, so a 5mm width is about 0.35mm²
Plenty of PCBs are only 1oz or even less.

Um, we in the UK have been calling our copper weight 1 oz, 2 oz for many many years, possibly longer than in the US, we still do.