weaker spring for some keys in model M?

[shallpion]

Hi, this is my first post in the forum so please forgive me if I am asking a dumb question I just received my first IBM model m 1391401 in my life and it has been in overall very good condition. I like it very much. Howver I noticed that there is one key that has a little weaker "ping" sound when pressed compared to the others. This keyboard has been partially bolt modded so I don't think it is a metal board separation issue, plus if were due to a weaker spot on the metal backplate it shouldn't affect only one key at all. I pulled the keycaps of it and compared it to the others nearby and realized that the buckling spring for this key is a little weaker compared to the others. It is not a big issue for me but since this is my first model M I would like to ask whether it is normal for some springs to be a little weaker compared to the others. The sound is only noticeable when you pay special attention to listen to it, and during normal typing it is barely noticeable at all and so far it doesn't seem to affect the feeling on fingers either.

I firstly thought of replacing the spring but then I realized I would probably dissemble then entire backplate to remove the spring and drum, not something I am ready to do given the fact that this is my first M

Thanks for any suggestions!

[Touch_It]

There is something called the chopstick method to replace a spring.  Don't have the time to look it up right now.  Also I have never tried it so do it at your own risk.  My thought would be a slight variation in the barrel plate aligning with the back plate, but if its partially bolt modded, maybe not, and the spring is slightly different.  It would explain why only 1 key is affected.  Honestly if it doesn't bother you, I wouldn't even try to replace it.  If it does bother you, you might want to try the chopstick method as you don't have to open the board to do so.

[chyros]

Each key has different acoustics due to their different locations on the board, so it's normal for all keys to not sound identical. Especially on a bolt-modded board it's to be expected that the tightening on the plate isn't 100% even throughout, either. If the keyfeel isn't affected I wouldn't bother to change it.

Springs shouldn't have a different weighting though. The IBM buckling spring design has surprisingly low tolerance for errors for such a simple-looking design.

[shallpion]

thank you so much for your responses, I just googled the so-called chopstick-of-death and made such a chopstick by myself. I then replaced the spring under that key ("p" to be specific) with key scroll-lock that I would never use. It took me a while to get the feel right. It appears there is a "sweet spot" for the spring to seat perfectly to have the "ping" sound, simply looking tight on the drum may not necessarily have that feeling. But anyway it finally worked and I cannot be happier now

Also thanks to chryos for your explanation as well.  In fact after I swap the spring under "p" key with scroll-lock I noticed that it sounds normal under scroll-lock. Then I got a little nervous that I suspected it was something else's issue about the bolt-mod. But after twisting the spring under "p" for a while they both worked euqally well and I couldn't tell either one being "weak". I guess the original issue was probably b/c the previous owner didn't get the spring under "p" in its' perfect position, or it somehow got loose during years' of use.

I will keep my chopstick for future use of coz! Thank you guys for the suggestion!

[chyros]

thank you so much for your responses, I just googled the so-called chopstick-of-death and made such a chopstick by myself. I then replaced the spring under that key ("p" to be specific) with key scroll-lock that I would never use. It took me a while to get the feel right. It appears there is a "sweet spot" for the spring to seat perfectly to have the "ping" sound, simply looking tight on the drum may not necessarily have that feeling. But anyway it finally worked and I cannot be happier now

Also thanks to chryos for your explanation as well.  In fact after I swap the spring under "p" key with scroll-lock I noticed that it sounds normal under scroll-lock. Then I got a little nervous that I suspected it was something else's issue about the bolt-mod. But after twisting the spring under "p" for a while they both worked euqally well and I couldn't tell either one being "weak". I guess the original issue was probably b/c the previous owner didn't get the spring under "p" in its' perfect position, or it somehow got loose during years' of use.

I will keep my chopstick for future use of coz! Thank you guys for the suggestion!

The spring was probably seated slightly out of place then. Like I said the margin of error on these switches is surprisingly small. Glad you got it fixed!

[shallpion]

Thank you again chyros. 

In case any inexperienced users like me needed to know what the chopstick should look like, I am attaching a picture of the one worked for me. One can make it longer at first then trimmed it down as needed b/c the tip should be neither too long or too short. Also while many said to twist clockwise to tighten spring, I found that one of my springs worked better with counter-clockwise twisting. Springs are not screws so they don't have to be twisted exactly the same way as screws. But no matter how one twists the springs, be gentle at first not to "wrap" it if it shows great resistence.