Bolt-modding Model M with glued membrane

[EDI]

So I'm trying to bolt mod a old 1390120 from 86, but the problem is that the membrane seems to be glued in to the backplate.

Should I try to remove the membrane from the backplate or is it possible to do the bolt mod without removing it?

I've done multiple bolt mods before, but never seen glued-in membrane before.

[E TwentyNine]

I don't see any reason why having the membrane glued to the backplate would interfere with a bolt mod.

[fohat.digs]

Are you talking about the rubber mat or the mylar sheets with the circuitry?

Unicomp refers to the rubber as the "blanket" and it does not serve any electrical purpose beyond padding and insulation. If that is what is stuck, I would soak it in water. Chances are, it was a sugar drink spill that got in there and hardened.

If you mean the clear layers with traces, you will have to be much more careful.

And, I agree, you should be able to do a bolt mod anyway. I have never encountered that and always took them apart and cleaned everything, but you could do it in place.

If you give up and just scrape it off, buy a new "blanket" from Unicomp for $10. It is thin white latex instead of the thicker black rubber, and I think it is better.

[EDI]

Are you talking about the rubber mat or the mylar sheets with the circuitry?

Unicomp refers to the rubber as the "blanket" and it does not serve any electrical purpose beyond padding and insulation. If that is what is stuck, I would soak it in water. Chances are, it was a sugar drink spill that got in there and hardened.

If you mean the clear layers with traces, you will have to be much more careful.

And, I agree, you should be able to do a bolt mod anyway. I have never encountered that and always took them apart and cleaned everything, but you could do it in place.

If you give up and just scrape it off, buy a new "blanket" from Unicomp for $10. It is thin white latex instead of the thicker black rubber, and I think it is better.

Fortunately it's not the rubber mat which is stuck. Just the nylon sheets and they have been glued in place.
It was probably some old practice since this Model M was manufactured in Feb 86

[fohat.digs]

Fortunately it's not the rubber mat which is stuck. Just the nylon sheets and they have been glued in place.
It was probably some old practice since this Model M was manufactured in Feb 86

I am curious, I have had at least 3 Ms from 1986 and none had this problem.

Are the 3 clear sheets glued together, and/or are they glued to the plastic barrel frame (aka chimneys in Unicomp-speak)?

I would be a bit concerned about getting tiny plastic shavings between these sheets where they could interfere with electrical contact.

[E TwentyNine]

Fortunately it's not the rubber mat which is stuck. Just the nylon sheets and they have been glued in place.
It was probably some old practice since this Model M was manufactured in Feb 86

I originally thought you meant only the lower sheet was glued.

This was never a practice for manufacturing.  There's no reason to and lots of reasons not to.

Are you sure that the keyboard didn't get some liquid inside it, maybe completely submerged, and the membranes are just stuck together due to that?

Got pics?

[EDI]

Here are some pics:

[fohat.digs]

I must be losing my mind. I thought that the rubber mat went against the plate.

[EDI]

I must be losing my mind. I thought that the rubber mat went against the plate.

Yeah but should I force the membrane off or just leave it be?

[E TwentyNine]

Was the keyboard working before you disassembled it?

[EDI]

Was the keyboard working before you disassembled it?

Yes it was fully functional except few numpad keys, which were working badly because of rivet loss in that area.

[E TwentyNine]

Looks clean inside.

If it was mostly working as it was, and you're fairly certain it was a rivet problem and not a trace problem, I'd leave well enough alone and do the mod.

Worse case scenario there's a problem in the membrane and you'll have to open it back up.

[E TwentyNine]

Also, do you have a picture of the bottom sticker on the keyboard case?

[EDI]

Also, do you have a picture of the bottom sticker on the keyboard case?

Here is picture of the rear label if you meant that.

[E TwentyNine]

Also, do you have a picture of the bottom sticker on the keyboard case?

Here is picture of the rear label if you meant that.

Show Image

Yep.  Should have said "label".   Nice board.

[vivalarevolución]

I just bolt modded a 1390120 and it had the same issue with the circuit sheets stuck to the backplate.  I thought they manufactured it this way.  After the bolt mod, everything works fine.  And everything worked fine before the bolt mod.

[E TwentyNine]

I just bolt modded a 1390120 and it had the same issue with the circuit sheets stuck to the backplate.  I thought they manufactured it this way.  After the bolt mod, everything works fine.  And everything worked fine before the bolt mod.

OK, this just got a little more interesting.  Never heard of this but I'm far from the knowledgebase of Model M factoids.

Are the individual sheets completely glued to each other except for the pad points?  Or are they only secured in certain spots?

[EDI]

I just bolt modded a 1390120 and it had the same issue with the circuit sheets stuck to the backplate.  I thought they manufactured it this way.  After the bolt mod, everything works fine.  And everything worked fine before the bolt mod.

Even though many people seems to disagree, I think the sheets are glued to the plate.
 

[E TwentyNine]

Even though many people seems to disagree, I think the sheets are glued to the plate.

I was one of the doubters.  I now believe you're completely correct.  Now I'm curious how the individual sheets are attached to each other.

[fohat.digs]

Even though many people seems to disagree, I think the sheets are glued to the plate.

Seeing is believing. That looks like a factory application.

[vivalarevolución]

I just bolt modded a 1390120 and it had the same issue with the circuit sheets stuck to the backplate.  I thought they manufactured it this way.  After the bolt mod, everything works fine.  And everything worked fine before the bolt mod.

OK, this just got a little more interesting.  Never heard of this but I'm far from the knowledgebase of Model M factoids.

Are the individual sheets completely glued to each other except for the pad points?  Or are they only secured in certain spots?

I cannot say if they are completely glued to each other.  I tried to pull them apart at one corner, and then I said, eh, that's enough.

[EDI]

I just bolt modded a 1390120 and it had the same issue with the circuit sheets stuck to the backplate.  I thought they manufactured it this way.  After the bolt mod, everything works fine.  And everything worked fine before the bolt mod.

OK, this just got a little more interesting.  Never heard of this but I'm far from the knowledgebase of Model M factoids.

Are the individual sheets completely glued to each other except for the pad points?  Or are they only secured in certain spots?

I cannot say if they are completely glued to each other.  I tried to pull them apart at one corner, and then I said, eh, that's enough.

Could you take a picture of the rear label in your Model M?

[pr0ximity]

Bumping this because I think it's an interesting change in the way some early M's were made, and I'd like to add another data point. My 1390120 from May 1986 also had its membrane glued. Here's the rear label:



From a different plant than EDI's.  I'm curious as to how common these glued membranes actually are, they're rarely referenced. Additionally, this reddit user's 1390120 from Jan 1987 did not have its membrane glued.

I am curious, I have had at least 3 Ms from 1986 and none had this problem.

fohat, do you have pictures of the rear labels for those boards? Were they 1390120's as well?

[fohat.digs]

Bumping this because I think it's an interesting change in the way some early M's were made, and I'd like to add another data point. My 1390120 from May 1986 also had its membrane glued. Here's the rear label:

Show Image

From a different plant than EDI's.  I'm curious as to how common these glued membranes actually are, they're rarely referenced. Additionally, this reddit user's 1390120 from Jan 1987 did not have its membrane glued.

I am curious, I have had at least 3 Ms from 1986 and none had this problem.

fohat, do you have pictures of the rear labels for those boards? Were they 1390120's as well?

Oh, how I love those old-school labels!

I have never had a 1390120 because I wanted LEDs, but my 1390131s were never glued.

[pr0ximity]

The plot thickens. My theory is that 1986 1390120's were the only M's with glued membranes.

Agreed on the label, I don't type on the board all that much, but I could never sell it because everything about it oozes sex.

[dorkvader]

I believe mine (march 3 1986) has a glued sheet as well. I suspect it is common on ones of a certain age..?

Maybe they changed over when they quit adding the mandolin crystal to the controller!