1200XL few keys still don't work after keyboard mylar fix

[nilla]

Hello again. I'm back with an update on my recently acquired 1200XL.

 

I finally got around to attempting the keyboard mylar fix, as shown in FJC's video. However, I am unable to get three keys to work: left shift, right shift, and control. All other keys seem to be working fine. Is this a known problem? I tried cleaning the silicone pads of these keys with some IPA (I've done this when cleaning the silicone button membranes on Gameboy Colors), but still no dice. Below are some images to hopefully help solve the issue.

Edited January 26 by nilla

[Beeblebrox]

@nillaThat's great. Only 3 keys is great progress.

 

So it will likely just be testing with the continuity function on a multimeter where any possible break(s) in the mylar tracks are for this on the matrix that connects them.

 

The shift keys will probably be connected to each other. 

 

There will probably be a break in continuity along a few of the mylar tracks that you might be able to see if you shine a bright light source behind, along with testing with the multimeter. Also make sure the traces on the pcb are ok and there aren't any microcracks.

 

Are you happy all of the fingers connecting the mylar to the pcb are 100% ?

Tbh I'd expect more keys along matrix to not function if it was issues with the latter, so check the mylar traces using the methods I mentioned.

 

 

Edited January 26 by Beeblebrox

[+kheller2]

I'm going to first ask how you are testing that they don't work.

those keys won't fire alone in the self-test, you need to press them with another.  In addition, i think they run on PIN 1 of the connector right to pokey.  Shift, CTRL and BREAK.

[ACML]

By looking at the PCB traces, I think your BREAK key might also be an issue.  The BREAK, CTRL and SHFT keys have a common trace.  You can test the CTRL and SHFT keys using the HELP keyboard function, but not BREAK.  To test BREAK, pop in a BASIC cartridge and at the READY prompt, press BREAK, the cursor should drop down one line.  If it doesn't respond, it too is affected.  If that is the case, you either have a broken trace in the mylar as Beeblebrox mentions above or if that one trace corresponds to one of the nine fingers that meet at the PCB, you may have not built up the carbon trace to the same height as the other 8 fingers and that no is not making contact. 

 

If BREAK does not work, the issue is on the green PCB side and likely not the mylar side.

 

 

 

 

Edited January 26 by ACML

[nilla]

2 minutes ago, Beeblebrox said:

@nillaThat's great. Only 3 keys is great progress.

 

So it will likely just be testing with the continuity function on a multimeter where the break in the mylar tracks are for this on the matrix that connects them.

 

The shift keys will probably be connected.

 

There will probably be a break in continuity along a few of the mylar tracks that you might be able to see if you shine a bright light source behind, along with testing with the multimeter. Also make sure the traces on the pcb are ok and there aren't any microcracks.

 

Are you happy all of the fingers connecting the mylar to the pcb are 100% ?

Tbh I'd expect more keys along matrix to not function if it was issues with the latter, so check the mylar traces using the methods I mentioned.

 

 

Hey @Beeblebrox. I went ahead and applied some more conductive paint to the fingers -- currently looking at the traces.

 

10 minutes ago, kheller2 said:

I'm going to first ask how you are testing that they don't work.

 

I'm using the self-test function keyboard test along with the atari basic cartridge.

[nilla]

Quote

those keys won't fire alone in the self-test, you need to press them with another.

@kheller2 I didn't know this. Bringing up the keyboard test and pressing SHIFT + a letter shows that both are indeed working! Along with that, BREAK works in the basic cartridge, as @ACML stated. CTRL works too:)

 

Thanks all! I think it's all working now.

[+kheller2]

http://www.atarimania.com/documents/atari_1200xl_owners_guide.pdf

 

Page 8.

 

Also, there is some other information in there useful for new folks.

[Beeblebrox]

50 minutes ago, nilla said:

@kheller2 I didn't know this. Bringing up the keyboard test and pressing SHIFT + a letter shows that both are indeed working! Along with that, BREAK works in the basic cartridge, as @ACML stated. CTRL works too:)

 

Thanks all! I think it's all working now.

Great. Sorry, I made the assumption you knew these keys only work in conjunction with others. 

Glad working. It's a fantastic keyboard. 

[nilla]

8 minutes ago, Beeblebrox said:

Great. Sorry, I made the assumption you knew these keys only work in conjunction with others. 

Glad working. It's a fantastic keyboard. 

No worries. This is my first time working on an Atari, let alone owning one. I wasn't around when Ataris were ahahaha

Edited January 26 by nilla

[Paul Westphal]

FYI -If a new mylar doesn't work, check the the two 4051's, Pokey and Pia.