Ping after foam replacement in IBM XT keyboard

[Hypersphere]

After doing a foam replacement in an IBM XT keyboard, I noticed that many of the keys now have a loud pinging noise -- a high-pitched reverberation that is separate from the actuation click. This keyboard did not have a noticeable ping before the foam replacement. I used 1/8" silicone foam, which is probably too thick (it required considerable force to slide the plates into position, even using a bar clamp and holding the plates together with spring clamps). Has anyone else noticed an increased ping after doing a foam layer replacement in an XT and/or other Model F keyboard? I am wondering if there is too much pressure within the plates; I suppose there is an optimal pressure.

[Muirium]

Strong ping is a positive indicator of the overall condition of a Model F, in my limited experience. The least pingy Fs I've seen are a couple of AT's and a heavily used XT that aren't as good as my XT or Kishsaver anyway. I've been lucky with my own.

But I've never used a new Model F, so this could be nothing…

[scottc]

I find this interesting. My AT is quite pingy, but it still feels great. Then again, it's the only F that I'm familiar with.

[Muirium]

Ping is probably a measure of tension in the plates. Worn buckling spring keyboards tend to show it with loose plates (especially Ms with their broken rivets). So Hyper's aptly excessive ping is a logical consequence of his super tightened plates.

Besides the sound, what's it feel like when typing, compared to before?

[Hypersphere]

Ping is probably a measure of tension in the plates. Worn buckling spring keyboards tend to show it with loose plates (especially Ms with their broken rivets). So Hyper's aptly excessive ping is a logical consequence of his super tightened plates.

Besides the sound, what's it feel like when typing, compared to before?

Yes, I suppose this is yet another example of the Three Bears lesson that things need to be "just right". If the plates are too loose or too tight, there can be negative consequences. I would have thought that with all the new padding from 1/8" silicone foam that metallic pinging would have been dampened, but such is not the case.

As for feel, it is difficult to assess because the pinging is so pronounced. I find it more pleasant to type on my other XT, which has not been modified other than a good cleaning and replacing keycaps to match the remapping; it has no noticeable ping -- just an agreeable strong click with each keystroke. BTW, the other XT does not have a Teensy; I am using a Hagstrom converter box, which works very well.

An interesting difference between my two XTs is that whereas they are both extremely solid with no flex or creaking of the case, if I do a percussion exam of the case (like a physician tapping on the chest or abdomen during a physical exam), there are no points at which the sound is hollow on the modded XT. In contrast, although the unmodded XT sounds solid over most of its surface, around the top center of the case there is some hollowness upon percussion.

[Muirium]

Okay, here's a couple of recordings I made last year. See how these sound in comparison:

SSK:

Kishsaver:

I include the SSK as an example of a fellow buckling spring but without the ping of Model F. My Kishsaver's got a nice load of it, although I was much slower typing on it back then before I fixed it up and installed Xwhatsit's epic creation. These days I'm as confident on both.

If you're interested in adding sound analysis to your repertoire, this is the (shiny metal) mic I use and recommend as a convenient USB condenser:

http://www.samsontech.com/samson/produc ... /meteormic

[Hypersphere]

Okay, here's a couple of recordings I made last year. See how these sound in comparison:

SSK:

Kishsaver:

I include the SSK as an example of a fellow buckling spring but without the ping of Model F. My Kishsaver's got a nice load of it, although I was much slower typing on it back then before I fixed it up and installed Xwhatsit's epic creation. These days I'm as confident on both.

If you're interested in adding sound analysis to your repertoire, this is the (shiny metal) mic I use and recommend as a convenient USB condenser:

http://www.samsontech.com/samson/produc ... /meteormic

Thanks for posting the recordings. Perhaps my sound system does not reproduce the sounds very well, but I do not notice the ringing/pinging from your KS. However, my modified XT rings and pings like mad. In fact, I can get the ringing by simply touching the keys lightly without actuating them.

Perhaps I could devise a way to tune the plates or cases on these keyboards akin to the tuning of a violin by moving the soundpost inside the body of the instrument.

Thanks also for the microphone recommendation. A colleague here has also recommended this particular mic.

[Hypersphere]

Update: I tried loosening the screws a bit on the back of the case, and this reduced the pinging somewhat. Thus, the acoustic properties of the keyboard are indeed affected by the overall tension in the plates and case. The XT case is held together by just two screws, which apply tension to the bottom steel panel, which in turn applies force to the back metal plate.

In addition, I tried the floss mod on some of the twangiest keys, and I found that this definitely works as advertised. I used Oral B Superfloss cut into approximately 14 mm pieces and inserted into the spring under each keycap. This results in a rather dead sound for the flossed keys. I haven't decided yet if I like it or if I would prefer the rather intense pinging and ringing.

[FergoTheGreat]

The metallic ping is the reason I use an XT over a Model M.

[Hypersphere]

The metallic ping is the reason I use an XT over a Model M.

Yes, I, also. I quite enjoy the metallic click and some level of ping that I have in my first XT. However, the second XT that I have refurbished with a new foam layer has a magnified ping beyond anything I have experienced before. I would not want to remove its character, but just to make it a bit more subdued. Perhaps I must reap what I sow: Hyperping for Hypersphere.

[Hypersphere]

I've been curious about the "floss mod" since first seeing posts about it. My hyperpinging XT seemed a good candidate, and today I completed the floss mod on it. I used ~14 mm segments of the fluffy section cut from Oral B Super Floss, inserted one each into the springs and replaced the keycaps. The only key that did not get flossed was the spacebar -- I didn't want to take the plates apart again in order to remove and replace the stabilizer wire. The spacebar had no noticeable ping anyway.

The floss mod does indeed work as advertised. The click is still there, but there is no trace of the former ping. After becoming somewhat accustomed to the ping, the sound after the floss mod seems a bit dead. I am not yet sure if I like it or not.

I am reminded of the song that Duke Ellington and Ella Fitzgerald made famous, which I now quote with a modification:

"It don't mean a thing if it ain't got that [ping] (doo-ah, doo-ah, doo-ah, doo-ah, doo-ah, doo-ah, doo-ah, doo-ah)."

On the other hand, the board still feels and sounds as solid as a steel brick -- perhaps even more so after removing the ping. If it turns out that I do not like the new pingless sound, it is always possible to remove the floss from each of the springs.