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geekhack Community => Keyboards => Topic started by: dschwarz2 on Mon, 11 May 2020, 22:47:49
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Hi everyone,
I'm waiting out the coronavirus with my family at my wife's childhood home, and I found an old Everex Step keyboard covered in crud under a bed. It cleaned up very nicely with isopropyl alcohol and compressed air. I've taken the keycaps off for cleaning but otherwise have not opened up the keyboard yet.
[attachimg=2] [attachimg=3]
I got a AT DIN5-to-PS2 adapter and plugged the keyboard into a computer. Lights work, keys work - mostly. Some are totally reliable (A, for example) but others are intermittent. For example, B, C, R, and others. I can type at a constant slow speed and moderate pressure, and sometimes the B key will register, sometimes, it will not. Sometimes C will register, sometimes it will not. Then I go back and type C again and it may work.
The attached text file shows my attempt to type the alphabet numerous times at a slow tempo and uniform pressure. You can see that some keys work more reliably than others. Next, my attempt to type the numerals above QUERTY keys at a slow tempo and uniform pressure. Finally, alphabet again, this time with capslock on. [attach=1]
Any idea what's going on here and how to fix it? My thoughts are:
1- Crud in the keyswitches (but I can't see or feel any in the affected keys; they seem the same as the others)
2- Momentary short or some other flaw in the PCB
3- Oxidation
4- Bad or marginal capacitors
I did read this excellent writeup by arapineau https://geekhack.org/index.php?topic=99509.0 (https://geekhack.org/index.php?topic=99509.0) which covers this exact keyboard.
Thanks for your help!
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I'm no expert on Hi-Tek 725, but I always start with what's simple myself. When the slider descends, this allows the contacts to come closer and closer together until they make contact and register a press (A coworker recently brought in an old Atari 800 and I noticed that Hi-Tek's high profile switches make this very easy to see if you remove the caps and depress the slider). If there's literally anything between those contacts that's preventing a good electrical connection, be it debris, or oxidation, I could see that possibly causing the problems you're experiencing. If you were able to carefully disassemble the problem switches and dig whatever gunk may be inside out of them, and make sure the contacts are clean, but see no change, then that eliminates that problem as the cause.
I have even had MX reds start acting up similarly to that if I haven't cleaned my board in a long time.
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Try the simple stuff first. I'd use electronic contact cleaner on the problem switches. The design of those switches is such that you can spray into them easily. I've used this product in keyboard switches many times with no effect on the plastic or any other problems.
https://www.amazon.com/CRC-05103-Electronic-Cleaner-11/dp/B000BXOGNI/ref=sr_1_2?dchild=1&keywords=CRC+05103&qid=1589296165&sr=8-2