New notes on boltmodding a model M

[xiphmont]

Partly for my own faulty memory, and partly for others to find (and discuss)...

I took some 'me' time this weekend and boltmodded a few of the model Ms in a pile in my basement (as well as my daily driver on my workstation)

I worked from the excellent boltmodding tutorials here and at deskthority.  After doing several, I noticed a few truths the FAQs don't mention.

1) the oldest model Ms appear to have the membrane bonded to the back plate.  Don't try to remove it unless you have a replacement handy :-)

2) I found one faq that mentioned 'the bolts should be at most finger-tight'. 
     2a) 'finger tight' for a 4mm bolt is probably a tad too loose, especially in the middle rows
     2b) and easy 'the bolt is too tight' test: when the keyboard barrel plate, membrame, hammers, rubber damper and backplate are reassembled, rock the assembly forward and backward.  The hammer springs should all fall forward and backward freely as the board is rocked.  Any spring that doesn't fall forward and backward freely is a problem
     2c) Overtightening a neighboring bolt is the most likely reason the spring won't move freely, but not the only possibility; a sagging rubber damper or a damaged hammer will casue the same symptom (and the same dead-feeling key(s)).
     2d) Seriously, use some threadlock.

3) The rubber damper that sits between the hammers and membrane should be perfectly flat.  Many old ones are not; they've bulged up between the key rows.
     3a) Adhesive transfer tape (eg, "Killer red Tape") can be used to hold a 'puffing' damper slightly stretched and perfectly flat for assembly.  Run a 1/8" strip just under each row's circular membrane contacts.
     3b) KRT will not harm the feel, and can renew 'dead' keys caused by a bluging rubber damper.

4) DO NOT BOLT THE FRONT ROW
     4a) Many FAQs mention it's not very important to bolt the very front row (in front of the spacebar), but i submit that doing so is actively harmful
     4b) The bolts will not clear the rivet cutouts in the keyboard base
     4c) the extra torque/levering needed to seat the key assembly into the case when the bolts are too deep exerts enough pressure on the lower row of keys to noticeably hurt the action of the lowest row.
     4d) The feel of the lower row (especially the lower arrow keys) will be similar to what happens when you accidentally remove the 'half-moons'; the travel is too short, the spring buckles too soon, and the 'ping' of the key is too shallow and indecisive.  They key feels 'dead'.
     4e) The lower row of plastic rivets/bolts isn't even needed-- once the keyboard is in its frame.  The frame will hold the assembly front together (check out a model M with all rivets in tact--- the lowest row of rivets are slightly loose!)

Cheers!

[fohat.digs]

Maybe my fingers are stronger than most people's, but finger tight has proven plenty tight for me. After all, the original is melted plastic that is often broken anyway. Tighter bolts make for stiffer key press, in my experience.

At the front, I have had much better success with small "self-tapping" screws so that I don't have to mess with removing material to make a place for the nut. Again, just snug but not tight. I have not always used them, they are a nuisance and expensive (10 of them cost more than 100 of the bolts), but I like everything connected, even if a bit loose.

I have had a couple of 131s from as early as mid-1986, and never experienced that thing with the rubber mat. (On the other hand, the majority of my Model Fs have their mats (admittedly a different material) partly or totally disintegrated.) Maybe yours were kept in an environment that caused it to deteriorate and stick. All my Model M mats have come off in pretty good shape.

[xiphmont]

I have had a couple of 131s from as early as mid-1986, and never experienced that thing with the rubber mat. (On the other hand, the majority of my Model Fs have their mats (admittedly a different material) partly or totally disintegrated.) Maybe yours were kept in an environment that caused it to deteriorate and stick. All my Model M mats have come off in pretty good shape.

The mats didn't stick to anything, just non-flat/puffed out a bit everywhere that they were't sandwiched between the barrel plate and membrane... as if the keyboard was stored upside down and it just sagged.  I hadn't seen it before either.  It still feels perfectly normal, but I guess it lost some stretch.  Or these keyboards were assembled differently... or it's just a materials defect...

But given what you said about Model Fs with disintegrated mats, I think I'll replace these rather than relying on the 'repair' holding.

[I had put off contacting Unicomp to see if they had parts given all the complaints about how slow they are to respond...  Decided to try, and in ten minutes, I have replacement mats on the way.  Hooray!]

[dorkvader]

[I had put off contacting Unicomp to see if they had parts given all the complaints about how slow they are to respond...  Decided to try, and in ten minutes, I have replacement mats on the way.  Hooray!]

Sweet! How much are they? I am wondering if they will sell me one that'll work on my F-122. I suspect they can, as they do make 122-key keyboards still.

Just another thing to add to my order when the Red/blue dyesubs come out.
RGB kits, keycap set, green keycaps, mats, USB controller, etc.

[xiphmont]

Sweet! How much are they?

For the 101 key M they charged $10.  But I think their minimum shipping is also like $10, so that's pretty pricey.  I got some extra stuff at the same time to even it out some.

Still pricey though--- almost better off getting a cheapy busted M off eBay.

[fohat.digs]

The rubber mats are completely different between the F and the M, and serve a different purpose.

Dorkvader, you need to make a new mat for your F. I got a sheet of foam at an art supply store and a 5/8" hole punch. I used spray paint and the metal plate to mark the holes, since I was painting my plate anyway. It worked great and was easy.

The Model F mat is basically foam, at least a couple of mm thick (at least when new!) with a rubbery skin on one side. The barrels actually rest, or "bed" might be a better term, into the mat, and the mat deforms deeply around them. Also, since the plate is a "front" plate, and the mat, and everything else, is behind the plate, and it needs that thickness and resilience to keep everything snug.

The Model M mat is a flat sheet of thin rubber, and probably serves mostly to shield the plastic membranes from the metal "back" plate, which is at the very bottom of the stack. I don't think it serves much mechanical purpose, and is probably far less critical than the F mat.