I took apart a Model M to try find why Ctrl and Shift key weren't working. I found that mylar trace sheet cracked where it bends before plugging into controller board.
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(Attachment Link)
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I've never tried to repair these before and need some guidance.
Searches here bring up copper tape, conductive pens and even windshield heater repair kits.
The copper tape seems to be the way to go, but I have a question. Since the tape has an adhesive on one side, won't the adhesive insulate rather than pass current?
Would this be the correct one to get?
http://www.kaptontape.com/Copper_Conductive_Tapes.php
I'll need to cut it to about 1mm thickness and am wondering if it will stick well enough being so small.
Any suggestions on how to make a pro repair is much appreciated.
There is nowhere to solder a lead to...the mylar will practically evaporate if you put that amount of heat near it.
The only option is something involving a conductive adhesive. I fortunately haven't found myself having to repair one of these guys in a while, but I did have an old container of a conductive glue that worked for repairing small breaks. The problem is if it flexes, the connection breaks or becomes intermittent, and the resistance is somewhat high so you need a lot of surface area to make a reliable connection.
If you do go the route of some kind of adhesive, lightly sand (even just a single pass) the surface of the trace for better adhesion.
My first suggestion would be to confirm that it works 100% by bridging the break with a paperclip or something just to see that there isn't another issue elsewhere. Unlikely, but worth confirming.
Rear window defrost repair products should do it, but remember that those defrost grids are essentially big resistors so I don't know how reliable that fix is. I've definitely heard of it being used before though.
oh... hmm those are the contact sheets.. I see, my mistake.. I thought they were just cables.
If you do go the route of some kind of adhesive, lightly sand (even just a single pass) the surface of the trace for better adhesion.
My first suggestion would be to confirm that it works 100% by bridging the break with a paperclip or something just to see that there isn't another issue elsewhere. Unlikely, but worth confirming.
Replacement membranes are only about $10 from Unicomp. They carry most of the old model membranes.
This http://www.radioshack.com/product/index.jsp?productId=3964901 (http://www.radioshack.com/product/index.jsp?productId=3964901) worked for me. I have completely removed the numpad cluster and rewired this with the circuitwriter to make the poor mans SSK. I also found it is pretty flexible and does not fall off/come off as expected. HOWEVER you have to follow some precautions:
This http://www.radioshack.com/product/index.jsp?productId=3964901 (http://www.radioshack.com/product/index.jsp?productId=3964901) worked for me. I have completely removed the numpad cluster and rewired this with the circuitwriter to make the poor mans SSK. I also found it is pretty flexible and does not fall off/come off as expected. HOWEVER you have to follow some precautions:
Great guide! and good to know Circuit Writer worked.
I used Circuit Works conductive pen (http://www.chemtronics.com/products/product.asp?r=1&m=2&id=7), and it didn't work for me. It was not flexible on curved surface and very brittle after it dried.Show Image(http://i.imgur.com/HapJA.jpg)
In the end I used copper tape to fix traces instead of Circuit Works and it worked. I'll try to use Circuit Writer and follow your guide if I have to do this job again.
Get Circuit Writer, avoid Circuit Works.
This http://www.radioshack.com/product/index.jsp?productId=3964901 (http://www.radioshack.com/product/index.jsp?productId=3964901) worked for me. I have completely removed the numpad cluster and rewired this with the circuitwriter to make the poor mans SSK. I also found it is pretty flexible and does not fall off/come off as expected. HOWEVER you have to follow some precautions:
Great guide! and good to know Circuit Writer worked.
I used Circuit Works conductive pen (http://www.chemtronics.com/products/product.asp?r=1&m=2&id=7), and it didn't work for me. It was not flexible on curved surface and very brittle after it dried.Show Image(http://i.imgur.com/HapJA.jpg)
In the end I used copper tape to fix traces instead of Circuit Works and it worked. I'll try to use Circuit Writer and follow your guide if I have to do this job again.
Get Circuit Writer, avoid Circuit Works.
I have a feeling that I have gone thru the brittle issue. See my notes #3, this is the problem. I suspect the seller sends with a reasonable amount of solvent/acetone base, but when we buy these things and apply to the mylar, amjority of the acetone is evaporated. I found it by mistake... after trying countless types of plastic solvent etc to glue plastic cabinets that they simply dont get the bonding strength not due to the bad glue... but due to a bad/unprepared surface. So you wipe the surface with acetone and it somehow creates a very thin melted surface or something. Now if you glue anything here, it is worse than JB-Weld. I have broken model-M pieces that I had to break as I could not unbond a surface just after 5 minutes of joining with the standard plastic binder.
The other thing is once you use the jewelers loupe you will discover that the conductive material is not uniform enough, and so it possibly needs a second coat. Here is a picture of my SSK track check it out. You cant remove it without a blade. Period. Checkout the below photo. Solid conductivity and bendability. You must prepare the surface before apply.
Unicomp does not carry SSK membranes (sadly). This appears to be one barrier to them continuing production of them.
You may be able to roll up a new membrane to fit in the case.
But the thread that would probably be of interest is :
http://geekhack.org/index.php?topic=29483.0