1200XL Keyboard Issues

[Tempest]

I pulled my 1200XL out of storage this week and discovered that some of the keys didn't work. After hitting them several times I got them to start working again (except for the J key), but they're intermittent at times. Is there an easy way to fix this (cleaning contacts or something of that nature) or is this a bigger issue like the Mylar keyboard issue that haunts the later XL systems?

[flashjazzcat]

You need to follow this guide:

 

http://www.retrobits.net/atari/keyboard.shtml

[Tempest]

Where can you get that silver paint? Is it 100% necessary or can you just clean those contacts? Is there a cheaper version of it?

[flashjazzcat]

I got the paint on eBay. I think some people have used car defogger paint. In any case: it's necessary, since the contacts where the perished glue has been removed are always damaged.

[Tempest]

Ok. What is the technical name of this product? Silver Paint isn't going to cut it as I just get results for paint that is silver. I'm assuming it's something like 'trace paint' or something of that nature.

[flashjazzcat]

Try "conducive paint" or "silver conductive compound".

[Tempest]

Would a conductive paste work or does it have to be paint? I have some Arctic Silver left over from when I was making my computer.

 

I also found this pen on Amazon. Seems like it should work: http://www.amazon.com/MG-Chemicals-841-P-Conductive-Resistivity/dp/B00DEEGYMM

[flashjazzcat]

Yeah that should work. Definitely don't use paste. You're aiming to build nice neat, permanent tracks.

[+bob1200xl]

I haven't tried it yet, but people say that the Bare conductive paint works well. You can get it from Jameco or RadioShack.

 

Some keyboards can be fixed by re-positioning the mylar, some require paint.

 

Bob

[Tempest]

I haven't tried it yet, but people say that the Bare conductive paint works well. You can get it from Jameco or RadioShack.

 

Some keyboards can be fixed by re-positioning the mylar, some require paint.

 

Bob

If that's true then that would be infinity cheaper. The Bare Conductive Paint is only $10 and available at the RS in the next building over from me.

 

What's the difference between the Bare Conductive paint and the Silver paint?

[+bob1200xl]

I would guess that the silver paint has a higher current capacity.

 

Bare paint is water based so allow for a reasonable drying time.

 

It looks thick. Don't apply too much.

 

Bob

[Tempest]

I would guess that the silver paint has a higher current capacity.

 

Bare paint is water based so allow for a reasonable drying time.

 

It looks thick. Don't apply too much.

 

Bob

I would imagine that there isn't much current going through a 1200xl keyboard. I'm guessing it will work just fine.

[ACML]

I haven't tried it yet, but people say that the Bare conductive paint works well. You can get it from Jameco or RadioShack.

 

Some keyboards can be fixed by re-positioning the mylar, some require paint.

 

Bob

I can vouch for Bare Conductive paint. I have used it to fix 2 800 and three 1200XL Mitsumi keyboards. The Craig Circuit Writer also works well, but is twice the price. As you have mentioned, the Bare is considerably thicker and I've found the best way to apply it is with a toothpick. Apply only a thin layer, making sure it is dry before you recombine the mylar, silicon spacer and PCB. You may find out that you have shorted two terminals or cracked a trace on the mylar when you disassembled it. Remember, it has a resistance so a simple continuity check with multi-meter may show an "open" (i.e. no beep), but it will still work. The resistance is enough to not satisfy the multi-meter. I apply, let air dry for a few hours, then test.

Edited May 23, 2014 by ACML

[willyvmm]

So. that guide was wroten over 10 years ago... At this moment almost averything has changed.

The biggest problem is to separate the 2 mylar(?) layers. Sometimes it is necessary to use hobby knive blade to separate them. Just put it flat on the mylar, and try to separate layers. A Beer od two will be very usefull. Try to do not separate the main connector, and do not cut traces !!

After you separate the 2 layers foil, use just standard cotton swab and firmly clean all contacts.

put it togeter ...and pray for better contact for next 10 years

Edited May 24, 2014 by willyvmm

[flashjazzcat]

I never yet saw a 1200XL keyboard with two mylar layers. If yours has a single membrane on the PCB, I can vouch for the use of a hairdryer to warm things up prior to peeling off the membrane. Loosens the glue and avoids tearing the silicone.

[Tempest]

Ok I started to follow the instructions, but as I'm trying to peel the mylar from the board it's tearing around the screw holes. I'm afraid to do any more as I don't want to damage it further. What am I doing wrong? Do I need to take the whole thing off if I'm only going to paint the connector fingers anyway?

[Tempest]

I'm a bit lost at what I'm looking at. I see the set of contacts on the left (the brown ones) in Figure 3, but not the ones on the right (the white ones). I also don't understand what figure 4 is supposed to be as I don't see two sets of contacts above each other. What one earth am I supposed to be painting? Maybe I need to send this out to someone?

 

Maybe I'm not understanding what 'mylar' and 'silicone' are. Is the silicone gasket the white stuff and the Mylar the clear plastic? If so, are you supposed to pull them both off the circuit board? The white stuff seems to want to tear where the screws were, can that cause serious damage? I just don't want to cause permeant damage to the keyboard.

[ACML]

Where can you get that silver paint? Is it 100% necessary or can you just clean those contacts? Is there a cheaper version of it?

I have fixed several 1200XL keyboards using BARE conductive paint. You can get it at Radio Shack for $10.

[ACML]

I'm a bit lost at what I'm looking at. I see the set of contacts on the left (the brown ones) in Figure 3, but not the ones on the right (the white ones). I also don't understand what figure 4 is supposed to be as I don't see two sets of contacts above each other. What one earth am I supposed to be painting? Maybe I need to send this out to someone?

 

Maybe I'm not understanding what 'mylar' and 'silicone' are. Is the silicone gasket the white stuff and the Mylar the clear plastic? If so, are you supposed to pull them both off the circuit board? The white stuff seems to want to tear where the screws were, can that cause serious damage? I just don't want to cause permeant damage to the keyboard.

You want to completely remove the Mylar with silicon gasket attached (yes, the white stuff is the silicon "spacer"). It's OK if it tears, just be gentle and use an exacto of toothpick to pry it free. As long as you can lay it back down is the same place, tears are OK.

1) Once you've removed the mylar with silicon gasket still attached to the mylar, you will see that the terminal connectors back on the PCB have a piece of tape about 1/4" x 1.5" (see lower right quadrant of firgure 3 - Retrobits.net).

2) That piece of tape attached to the PCB has 8 or 9 gaps with conductive material. You want to remove the skinny piece of tape and discard it. Underneath will be, should be, nice gold contacts.

3) Take a cotton ball with some 90% alcohol and clean up those PCB contacts and all the pad contacts on the PCB (not the mylar with silicon gasket).

4) Where do you apply the conductive paint? Look at figure 3 on the Retrobits article. On the right side just above the 16 pin reverse/side soldered in chip, there is the mylar spacer with the alternating dark brown and white stripe thin rectangle (on the mylar). Fat white, eight skinny white and another fat white little silicon stripes. In between the white spaces 9 dark brown stripes. That's what you are going to paint over with conductive paint.

5) But first you need to make sure you didn't break any of the dark conductive traces when you removed it from the PCB. Take a multimeter and set is for continuity (short gets a beep and open is silence. Trace one at a time the 9 dark brown terminal pads to each key spot on the mylar. Verify continuity. If you have an open, the trace somewhere between the two points you are touching has a break. You may have to peel a little white silicon to find it. Hopefully you won't find any breaks.

6) Using a toothpick carefully apply the BARE conductive paint on those 9 dark brown stripes on the mylar. These are the mylar terminal connections that will make contact with the gold terminal stripes on the PCB. These 9 stripes are 90%+ reason for flaky 1200XL keyboard.

7) IMPORTANT. Be patient and let dry. It will take a few hours (3-4).

Once dry, lay the mlyar with spacer back onto the PCB. I next use blue painters tape to hold it in alignment for a quick test. Install in 1200XL and try out the keyboard in self test (HELP MENU). All keys should register except the BREAK key. The BREAK key uses a special interrupt and does not register on the HELP TEST. Yuo may need to apply a little pressure on the contact point where you painted.

9) If it checks out, remove the blue painter's tape if you want and reassemble keyboard.

 

BARE conductive paint is graphite based and dries hard. The Criag CircuitWriter pen used suspended silver I think. Both will work and I used both with success. The reason you want it to dry before testing is that if it does not work or you accidentally shorted two of the 9 terminals with paint, the paint will be dry and wont stick to the PCB. Hope this helps!

Edited June 19, 2014 by ACML

[Tempest]

That helps a bunch! Thank you. I just wanted to make sure I was doing this the right way and not destroying the keyboard. I'll give this a shot tonight.

[Tempest]

It's working!