Carbon Contact pad repair

[RileyKA]

I'm a retro game and electronics hobyist. as a retro gamer I like to have original controllers for these consoles.
as you may know often carbon contact pads or carbon traces were used on the PCBs for the button contacts. many of these have worn down over time.

Is there a reliable way to repair these contacts after the carbon has been worn away.

Barring that are there any PCB manufacturers that would still do carbon pads if I were to design a replacement PCB, or do you think the carbon would even be necessary? could the contacts be replace with HASL pads or would gold plating be required?

[doktori]

Hi - what I use is a mix of powdered graphite & glue - you can make it thick or thin.
Powdered graphite is sold as a lock lubricant at auto parts stores.
You must use a non-toxic glue such as Testors "Non-Toxic Cement for Models"  # 3521
Probably find it at a hobby shop. 

The non-toxic glue will be conductive when dried, all other glues I've tried don't work.

Hope this helps.

[tooki]

I'm a retro game and electronics hobyist. as a retro gamer I like to have original controllers for these consoles.
as you may know often carbon contact pads or carbon traces were used on the PCBs for the button contacts. many of these have worn down over time.

Is there a reliable way to repair these contacts after the carbon has been worn away.

Barring that are there any PCB manufacturers that would still do carbon pads if I were to design a replacement PCB, or do you think the carbon would even be necessary? could the contacts be replace with HASL pads or would gold plating be required?

You can absolutely just use exposed HASL or ENIG. Carbon is often used for controllers, remotes, because it can be cheaply screen-printed on, rather than having to etch PCBs.

[TimFox]

Have you tried "Aquadag", a colloidal suspension of graphite particles in water?  It can be applied with a small brush.
Traditionally, this was used to coat the interior of cathode-ray tubes (driving off the water after application).
https://www.palmerholland.com/Assets/User/Documents/Product/45506/7432/MITM09837.pdf

[floobydust]

It's not so much the carbon print that wears out, it's the conductive keypad.
I've tried many fixes, conductive glues, metal foils etc.and best so far is to just buy a "keypad repair kit" from eBay they have an assortment of 1.5-10mm dia. pads that I silicone glue to the old keypad.
The travel is reduced but they work and last.

First I soak the whole thing (remote) in some dish-soap and water and use a toothbrush for clean up. But not too rough to scrape off the carbon print. It's usually food and pop that are in there.

[m3vuv]

what sort of perv poops in remote controls??

[richnormand]

You might look at electron microscope  (SEM) prep colloidal graphite liquid.
It is used to create a conductive glue to mount or glue samples on SEM stubs.

For example I have the Ted Pella 16053 Pelco colloidal graphite in the isopropanol base.
It dries quickly and is nicely conductive.
Cost about $8US for 30g.

https://www.tedpella.com/technote_html/16053%20TN.pdf
http://www.tedpella.com/pdfs_html/Adhesives-Conductive.pdf
https://www.tedpella.com/SEM_html/JEOL-Essentials.aspx

[abdulbadii]

get from extra spare part of a carbon brushed tool, would add help is conductive ink marker, glued after fix is finish to confirm its etching

[Cerebus]

Most, but not all, black India Ink is conductive when dried. The ones that are not reliably conductive are in the minority. Black India Ink is, of course, a variation on the 'powdered carbon in glue/binder' theme, but has the advantage is that you can find it in any art shop.

I've used India Ink successfully in the past to repair carbon tracks on PCBs, repair the pads on conductive buttons (wears faster over time than the original because of flexing), and to make holes conductive for through hole plating.

I think the brand that I've used successfully most recently is "FW", but I can't find which "somewhere safe" I've put it and thus can't conclusively confirm memory that at the moment.

[floobydust]

Modern keypads just have conductive paint on the keypad, good old ones had a conductive silicone rubber button. The paint is shit, Sony remotes died after 2 years. It just wears off fast.
To fix, I tried conductive paints such as discontinued MG Chemicals 8339 - Keypad Repair Kit and found it was just too hard, did not flex and just crumbled and fell off the keypad. Cyanoacrylate glue with the graphite pen was too crunchy. The issue is the conductive paint has to be able to flex .
Adafruit sells $60 circuitworks silver ink pen but I haven't tried it.

I've also tried cutting pieces of conductive plastic Velostat (like ESD bags are made of) but it is polyethylene and extremely hard for glue to stick to it. So that was also a fail.

[RileyKA]

thanks for all the input, I have some good ideas to try now.

[BrokenYugo]

I have no idea if they're any good, but you can get a "rebuild kit" (new rubber domes) for many vintage controllers, many on eBay.

[tooki]

Modern keypads just have conductive paint on the keypad, good old ones had a conductive silicone rubber button. The paint is shit, Sony remotes died after 2 years. It just wears off fast.
To fix, I tried conductive paints such as discontinued MG Chemicals 8339 - Keypad Repair Kit and found it was just too hard, did not flex and just crumbled and fell off the keypad. Cyanoacrylate glue with the graphite pen was too crunchy. The issue is the conductive paint has to be able to flex .
Adafruit sells $60 circuitworks silver ink pen but I haven't tried it.

I've also tried cutting pieces of conductive plastic Velostat (like ESD bags are made of) but it is polyethylene and extremely hard for glue to stick to it. So that was also a fail.

How about cutting little disks of the self-stick, woven nickel tape sold as EMI shielding? It’s very cheap on Ali.

[tooki]

what sort of perv poops in remote controls??

he wrote pop (as in, sweet, non-alcoholic fizzy drink), not poop. 

[floobydust]

Remote controls and video game joysticks are usually full of dirt, hair, food and dried out juice or drinks. I find that's a main reason they are not working, in addition to cracked solder joints or worn out keypads. Soda or pop, kids put them in their mouths... generally yucky.

Best was in the repair shop, a TV remote had almost all solder joints cracked and the case was cracked, the boss told me husband and wife were fighting, he throws the remote at her and she ducks, it hits the brick fireplace. "Can you fix it?" 

The keypad repair kits (pic) with assorted size discs are working great for me. For square pads, I just silicone glue on a larger round pad and use side cutters to carefully trim the shape - without nicking the keypad - to the square or rectangle.
Chemtronics CircuitWorks Rubber Keypad Repair Kit CW2605 looks worth trying but USD $28/CAD $41 is a bit much.
I have not tried nickel tape, as long as it's not too hard or it will trash the carbon print in no time.

Coleco joysticks have (metal) switches in them, I pull a piece of paper through the contacts to wipe off oxide and they are good.

[scopeman]

I use Neolube #2. You can get it from MicroMark. I have fixed dozens of carbon based contacts with it.

Sam
W3OHM