Building an OSI 542 Rev C Keyboard

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Jeff
Posts: 244
Joined: Fri Mar 07, 2014 4:44 am
Location: British Columbia, Canada

Building an OSI 542 Rev C Keyboard

Post by Jeff » Tue Oct 30, 2018 4:49 pm

Attached is the component layout and parts list.
Attachments
Parts Layout.pdf
(1.95 MiB) Downloaded 4 times
Keyboard Parts List.pdf
(21.95 KiB) Downloaded 5 times
542C Layout.jpeg
542C Layout.jpeg (1.63 MiB) Viewed 205 times
Last edited by Jeff on Wed Nov 07, 2018 3:43 am, edited 3 times in total.
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Jeff
Posts: 244
Joined: Fri Mar 07, 2014 4:44 am
Location: British Columbia, Canada

Re: Building an OSI 542 Rev C Keyboard

Post by Jeff » Tue Oct 30, 2018 6:55 pm

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gekaufman
Posts: 30
Joined: Mon Nov 23, 2015 12:57 pm

Re: Building an OSI 542 Rev C Keyboard

Post by gekaufman » Mon Nov 05, 2018 3:58 am

Jeff -

Thanks for all of your hard work putting this together.

I think there's a typo on the Parts List. U1A is a SN74LS193N, not a SN74LS139N as listed.

Curious if there is any reason that U1C, U1H really need to be 7475 (instead of 74LS75)?

- Gary

Jeff
Posts: 244
Joined: Fri Mar 07, 2014 4:44 am
Location: British Columbia, Canada

Re: Building an OSI 542 Rev C Keyboard

Post by Jeff » Wed Nov 07, 2018 3:48 am

Hi Gary,

Thanks for double checking my work. I have made the correction of the incorrect U1A chip and attached the revised file to Post # 1.

Regarding the 7475 vs 74LS75... I do not know the answer, I DO KNOW that my original 542C had those different IC's so the original engineer must have had a reason. I also checked the original schematic and they are listed different on it as well.

Thanks again!
/Jeff
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gekaufman
Posts: 30
Joined: Mon Nov 23, 2015 12:57 pm

Re: Building an OSI 542 Rev C Keyboard

Post by gekaufman » Thu Nov 08, 2018 7:54 pm

Jeff -
Thank you, the parts list was a wonderful help. I have literally many hundred thousand military resistors (from a purchase of an electrics supply that was going out of business) but it's nice to have a pick list. Even had the 10M part!

I did have two 7475's left in my bins, so went with the "correct" part.

Finished up the keyboard last night - Hopefully will have time to test this weekend, and anxiously awaiting the Keycaps.

- Gary

dave
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Re: Building an OSI 542 Rev C Keyboard

Post by dave » Fri Nov 09, 2018 5:29 am

For those of you who have built either the klyball 542c replica or the klyball 600D replica:

There's a bit of freedom for the keys to shift and rotate before they are soldered in. What techniques have you used to hold the keys straight and parallel before soldering them in place? Or has that not been a problem?

I have replaced some of the Futaba keys on an original keyboard, and found it difficult to get the replaced keys straight. I could have tried placing the keycap on the switch and using a flat edge--like a ruler--to align the keys before soldering, but didn't think of it at the time.

Thanks,

Dave

Klyball
Posts: 175
Joined: Tue Dec 09, 2014 12:53 am

Re: Building an OSI 542 Rev C Keyboard

Post by Klyball » Sat Nov 10, 2018 6:19 am

Are you using the keys with the 3 plastic pins + the 2 posts , the one I have plug in straight and stiff?
Replica 600 Rev D:8K,CEGMON
Replica 610 Rev B: 24k,MPI B-51 with Custom Data separator D-13
510 on the bench/replica 582 backplane/replica 470a /replica 555/original 570B/2 x Shugart 851
Ongoing : 630 ,620 ,510,542c,custom 590,SA1200,592,594,596,598

gekaufman
Posts: 30
Joined: Mon Nov 23, 2015 12:57 pm

Re: Building an OSI 542 Rev C Keyboard

Post by gekaufman » Sat Nov 10, 2018 1:56 pm

I've ordered cheap (probably counterfeit) Cherry MX switches from AliExpress. They only have a center post and the two solder connectors.
About 1/2 arrived with a small solder tab - a bit more difficult to align. The other 1/2 arrived with a larger stiff post that mounted nicely. Ironically they were mixed in the same bag.

https://www.aliexpress.com/item/10Pcs-3 ... 14611.html

Don't pick Yanwen for shipping, China Post is MUCH quicker.

I did find a source for the locking keyswitch!
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https://cartel.ltd/shop/mx-lock/

They are very nice, $6.00 each and a very reasonable $2.85 shipping. Arrived quickly and well packed.

- Gary

Jeff
Posts: 244
Joined: Fri Mar 07, 2014 4:44 am
Location: British Columbia, Canada

Re: Building an OSI 542 Rev C Keyboard

Post by Jeff » Mon Nov 12, 2018 7:23 pm

dave wrote:
Fri Nov 09, 2018 5:29 am
There's a bit of freedom for the keys to shift and rotate before they are soldered in. What techniques have you used to hold the keys straight and parallel before soldering them in place? Or has that not been a problem?

Thanks,
Dave
Step 1: solder one pin of each key
Step 2: with a helper, have the helper hold each key "square" to the board, while you reflow the solder on the one pin. Then solder the second pin.
Step 3: Provide beer to helper as a reward.

A bit of a brute force solution, but it worked for me.

/Jeff
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