Page 1 of 1

Pravetz KBD-8A

Posted: 28 Jan 2014, 19:17
by BlueBär
1.jpg
1.jpg (226.21 KiB) Viewed 3589 times
So I recently got this keyboard from Ebay after somebody posted it here. The keyboard stems from a Pravetz 8A computer, which is from what I understand the Bulgarian counterpart of the Apple IIe. The 8A was build between '86 and '88. If you want more information about it here's what I have found: http://www.pravetz.info/pravetz-8a.html

When it arrived it was extremly dirty and the keycaps were in a disgusting condition. For those who never bought an old keyboard, the first step is usually to put the keycaps in some warm water with dental tablets. They didn't really help this time and I had scrub each keycap - in hindisght that was a good decision since the legends are engraved. The keycaps are not doubleshot and probably ABS. They have a slightly spherical profile and feel very solid.
2.jpg
2.jpg (241.96 KiB) Viewed 3589 times
The keyboard features some cross-stem switches (not MX compatible), most of them with black housings, but with some brown and beige housings as well. The switch on the spacebar has a grey stem and feels heavier, but I couldn't feel a difference between the different housing colors, I don't think they make a difference. I don't know what exactly that is on top of the grey stem but it didn't come off. The enter key is the only key that uses two switches.
5.jpg
5.jpg (289.21 KiB) Viewed 3589 times
Now to the switches. As you can see the switches are secured with some screws on the PCB. I don't think there's an option to plate mount these switches.
10.jpg
10.jpg (328.56 KiB) Viewed 3589 times
From the outside you can already see the most important part of the switch, the reed switch. Opening a switch is not as easy as you would think, there's a part of the housing molten so that it doesn't open without scraping a bit of the molten part away. Hard to explain, but worse than glue. There's also an additional tiny copper pin that goes through a tiny hole to prevent opening it as well. If you noticed, one of the legs to fix the switch on the PCB broke off :?
12.jpg
12.jpg (260.25 KiB) Viewed 3589 times
13.jpg
13.jpg (233.41 KiB) Viewed 3589 times
The switch inside is quite simple, a magnet is attached to the slider and goes next to the reed switch when the key is pressed. A reed switch works with two very small metal plates that connect when a magnet is brought nearby. The slider itself only hits the bottom of the housing, it's not really clear on the photos.
15.jpg
15.jpg (397.31 KiB) Viewed 3589 times
16.jpg
16.jpg (287.26 KiB) Viewed 3589 times
18.jpg
18.jpg (233.04 KiB) Viewed 3589 times
19.jpg
19.jpg (296.08 KiB) Viewed 3589 times
And that's it! Here, have a typing video:
There's a few more photos in my thread on Geekhack and I can take some more if needed ;)

Posted: 28 Jan 2014, 20:48
by HaaTa
Yay, now I don't have to worry as much taking pics of this one :P

Yours also looks in better condition :D

Posted: 28 Jan 2014, 20:56
by kint
Very atmospheric video. I like the sparkling keycaps and the mellow movement of the shaddows on the left. Did you type on it while lying on the floor? :D Nice keyboard too. :)

Posted: 28 Jan 2014, 21:04
by Muirium
For engraved caps, they look pretty damn good. Better than those crazy bandy-legged LEDs! Sounds quite nice too in the video. The space bar stabiliser is refreshingly quiet compared to many 80s boards. Could still use a little lube, though.

Posted: 28 Jan 2014, 23:36
by nourathar
great pictures and video, and that board looks good too ! would love to try reed switches one day..

Posted: 28 Jan 2014, 23:45
by mr_a500
Yes, I like the lighting in that video. I wonder if those keycaps were originally white and the plastic yellowed or if "butter yellow" was the intended colour (doesn't look as bad as most yellowing). I didn't think they still did engraved keycaps in the late 80's. Eastern European countries were obviously slower to modernize. (which is certainly good for keyboards)

Posted: 29 Jan 2014, 00:19
by BlueBär
HaaTa wrote:Yay, now I don't have to worry as much taking pics of this one :P
:lol:
kint wrote:Very atmospheric video. I like the sparkling keycaps and the mellow movement of the shaddows on the left. Did you type on it while lying on the floor? :D Nice keyboard too. :)
The sparkling was actually not intended and I just noticed it when I cut the video :)
The keyboard lies on the floor with me kneeling in front of it.
Muirium wrote:For engraved caps, they look pretty damn good. Better than those crazy bandy-legged LEDs! Sounds quite nice too in the video. The space bar stabiliser is refreshingly quiet compared to many 80s boards. Could still use a little lube, though.
The caps have a long long cleaning session behind them, they were disgustingly dirty (this picture is still harmless, especially in comparison to what amount of dirt was on the switches) when they arrived.
The stabilizer definately needs lube, but I'll do that when I decide the fate of the board ;)
I kind of want to replace the springs with new ones but don't know where I could find some that will fit.
mr_a500 wrote:Yes, I like the lighting in that video. I wonder if those keycaps were originally white and the plastic yellowed or if "butter yellow" was the intended colour (doesn't look as bad as most yellowing). I didn't think they still did engraved keycaps in the late 80's. Eastern European countries were obviously slower to modernize. (which is certainly good for keyboards)
I think they were always a bit cream colored but not as much as they are now. I don't mind, the current color is quite pleasant and the yellowing is even.

Posted: 29 Jan 2014, 01:28
by dorkvader
Hmm, the keycaps look like they might have been doubleshot as blanks and the legends then engraved. It's not too uncommon to see, especially for boards with really funky legends. Care to check?

Anyway: thanks very much for posting this keyboard and such good pictures! I rather like reed switches, and these look to be rather nice. Good find!

Posted: 29 Jan 2014, 01:49
by BlueBär
dorkvader wrote:Hmm, the keycaps look like they might have been doubleshot as blanks and the legends then engraved. It's not too uncommon to see, especially for boards with really funky legends. Care to check?
Nope, caps aren't doubleshot. Also quick thickness comparison with Triumph-Adler caps (should be the same as thick Cherry/GMK/BSP). Sorry just Nexus 4 quality but I think it will do :)
IMG_20140129_013908.jpg
IMG_20140129_013908.jpg (573.86 KiB) Viewed 3513 times
dorkvader wrote:Anyway: thanks very much for posting this keyboard and such good pictures! I rather like reed switches, and these look to be rather nice. Good find!
Thanks!

Posted: 29 Jan 2014, 14:43
by woody
Yup, reed switches were the norm for most of the Pravetz-8 series: 82, 8M, but not 8C. Not sure about 8A, 8E, because they're too rare. Not sure about 8D, at least later versions weren't reed switches.

They have this very pleasant faint "click" upon closing the contact. I had to replace a reed switch or two because of chatter, which could've just been a faulty/marginal debouncing in the keyboard controller, too.

Posted: 03 Feb 2014, 19:13
by phosphorglow
What a fantastic looking board - I love the engraved caps. Super neat switch mechanism. (Neat looking machine too - the texture on the case looks cool).