Stubborn Rust on a Motherboard

[tecknerd]

Hi everyone.  I purchased a Sears Video Arcade II a while back and opened it up to find a lot of rust on the RF shield and the areas where it touches the motherboard.  I ended up soaking the RF shield in vinegar and painting it to try and give it some life back, at least until I can find a replacement.  It was pretty bad and there was no way it would keep the factory shine after removing the rust in any way.  I've been cleaning up the areas on the motherboard that I mentioned with 91% alcohol and switching between using a toothbrush, a Q-tip, and those blue shop paper towels soaked in the alcohol, but there is some rust that is being stubborn to come off.  I wanted to get some advice on how to get the remainder of the rust off, or if you all think it won't be possible.  I've included some pics to show what I'm dealing with.  Thank you in advance for all your help and input.  

[+Andrew Davie]

I have no idea what it would do to a circuit board, but stuff called CLR does wonders for rust stains. I guess you could be extra-careful and dab a bit on an area at a time with a cotton-tip and clean it of with isopropyl alcohol immediately after the rust has been "neutralised". Use at your own risk. In other words, in a court of law I'll restate my exact advice, which is "don't do this". Let me know how it goes...

[Keatah]

In the past I've used a small wire-brush or simply scraped it away. You can even use a small screwdriver or pin. There's always the option of reflowing it to refinish the surface.

 

I also see some rust stains on the green part of the board, more specifically the copper plane with green resist/insulation where nothing was etched at the factory. Hopefully none of the rust got between anything and it will come off with rubbing, but DO NOT scrape there or you will cause the green insulation to flake. then you're gonna pissed.

Edited February 19, 2020 by Keatah

[tecknerd]

Thanks for the advice guys, I really appreciate it.  Also thanks for pointing out the additional rust, I hadn't noticed it.  

 

22 hours ago, Keatah said:

In the past I've used a small wire-brush or simply scraped it away. You can even use a small screwdriver or pin. There's always the option of reflowing it to refinish the surface.

 

I also see some rust stains on the green part of the board, more specifically the copper plane with green resist/insulation where nothing was etched at the factory. Hopefully none of the rust got between anything and it will come off with rubbing, but DO NOT scrape there or you will cause the green insulation to flake. then you're gonna pissed.

Keatah, do you have any suggestions on how to reflow the area?  Thanks again.

[Keatah]

Well, one way might be to use a large capacity soldering iron, not necessarily a high-wattage one. And use it as a shovel to push a piece of copper braid around. With some flux. This is the equivalent of mopping the floor so to speak. Probably the safest. It reflows the immediate area underneath the braid and will absorb some the rust.

 

But, you know what, it doesn't have to be perfect. These larger area ground planes are usually purely functional.

Edited February 20, 2020 by Keatah

[Voxel]

What Keatah, said above, reflow!

 

It's worked for me in the past.

[christo930]

On 2/17/2020 at 4:01 AM, tecknerd said:

Hi everyone.  I purchased a Sears Video Arcade II a while back and opened it up to find a lot of rust on the RF shield and the areas where it touches the motherboard.  I ended up soaking the RF shield in vinegar and painting it to try and give it some life back, at least until I can find a replacement.  It was pretty bad and there was no way it would keep the factory shine after removing the rust in any way.  I've been cleaning up the areas on the motherboard that I mentioned with 91% alcohol and switching between using a toothbrush, a Q-tip, and those blue shop paper towels soaked in the alcohol, but there is some rust that is being stubborn to come off.  I wanted to get some advice on how to get the remainder of the rust off, or if you all think it won't be possible.  I've included some pics to show what I'm dealing with.  Thank you in advance for all your help and input.  

If it ain't broke, don't "fix" it!

If you makes you feel any better, paint the areas with a conductive pen.

 

Seriously. Leave it alone. Certainly don't go putting chemicals on it, especially if it already works.  It's going to be nice and shiny inside of the screwed together case.  It's not like there is a clear plastic case.

[tecknerd]

Thanks everyone for your suggestions and inputs.  I'm going to look more into each method and see which one I do.  I'm still new at trying to fix and restore consoles so your experiences and advice are really appreciate.  

[+Stephen Moss]

On 2/20/2020 at 7:42 AM, Keatah said:

Well, one way might be to use a large capacity soldering iron, not necessarily a high-wattage one. And use it as a shovel to push a piece of copper braid around. With some flux. This is the equivalent of mopping the floor so to speak. Probably the safest. It reflows the immediate area underneath the braid and will absorb some the rust.

What would it be re-flowing? Standard PCB is a copper track that is tin plated to prevent verdigris, as far as I know the tin plating will not re-flow when heated using a soldering iron otherwise it would flow off the component legs during soldering. 

 

At one time there used to be erasers with two ends, a standard pink rubber end and a grey more abrasive end, if you can still get them perhaps the abrasive end would get it off or try rubbing with a little wet & dry sand paper. You might also remove a little of the surrounding tin plating but you can replace it by going over it with a conductive pen, the conductive pen may not look quite the same as the original tin plating but with the case on you won't see it anyway. 

[Keatah]

1 hour ago, Stephen Moss said:

What would it be re-flowing? Standard PCB is a copper track that is tin plated to prevent verdigris, as far as I know the tin plating will not re-flow when heated using a soldering iron otherwise it would flow off the component legs during soldering.

That's right. Forgot to mention using some solder if none is present.

 

An eraser sounds basic and good, I'm opposed to sandpaper unless its real fine. It will leave debris that is more annoying to clean than an eraser.