Building an OSI 502B CPU Board

Jeff
Posts: 330
Joined: Fri Mar 07, 2014 4:44 am
Location: British Columbia, Canada

Building an OSI 502B CPU Board

Post by Jeff » Tue Apr 02, 2019 3:08 am

Aa part of my C4P Replica, I am building up a 502 CPU board.

Does anyone know how to configure the Monitor Rom Selects at U15? I have searched for documentation and cannot find any.
Monitor Rom Selects.png
Monitor Rom Selects.png (1.29 MiB) Viewed 1906 times

EDIT: Found my answer in an earlier post: viewtopic.php?t=327

/Jeff
Last edited by Jeff on Thu Apr 04, 2019 5:11 pm, edited 1 time in total.
Image

Jeff
Posts: 330
Joined: Fri Mar 07, 2014 4:44 am
Location: British Columbia, Canada

Re: Building an OSI 502B CPU Board

Post by Jeff » Tue Apr 02, 2019 4:05 am

Here is a layout I have created.
502 Layout small.jpg
502 Layout small.jpg (1.44 MiB) Viewed 344 times
[REVISED to show R74, missing trace, and needed mods and jumpers.]

/Jeff
Last edited by Jeff on Tue Sep 03, 2019 3:37 pm, edited 2 times in total.
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waltermixxx
Posts: 118
Joined: Sun Feb 03, 2019 10:31 pm

Re: Building an OSI 502B CPU Board

Post by waltermixxx » Tue Apr 02, 2019 10:51 am

Damn I soldered in my 24 pin sockets last night before this post, what are the mods with the little x and gray wires?
Turning into quite an OSI Junkie (HTFDTH?) Superboard II REV B-40K, 9600b, HC-05 Bluetooth, Superboard II Rev D, C4P rebuild- 502, 542c, 540B. :)

Jeff
Posts: 330
Joined: Fri Mar 07, 2014 4:44 am
Location: British Columbia, Canada

Re: Building an OSI 502B CPU Board

Post by Jeff » Tue Apr 02, 2019 2:36 pm

To use 2716's in 502 board

U6
1 cut trace between U6-18 and U6-21 topside
2 connect U6-18 to U5-18 on bottomside

Above U7
3 cut bridge at W4 topside
4 connect center of W4 to other position (gnd)

Above U9
3 cut bridge at W8A topside
4 connect U9-18 to U8-18 on bottomside

U17
6 remove U17 (74LS04)
7 add jumpers on U17 socket
3-4, 5-6, 8-9, 10-11, 12-13

Layout:
502 Board 2716 Mod.jpeg
502 Board 2716 Mod.jpeg (1.05 MiB) Viewed 1893 times
Instructions:
502 Use 2716 Eproms.pdf
(30.56 KiB) Downloaded 100 times

An earlier post on this topic: viewtopic.php?t=111

/Jeff
Last edited by Jeff on Thu Apr 04, 2019 5:10 pm, edited 1 time in total.
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waltermixxx
Posts: 118
Joined: Sun Feb 03, 2019 10:31 pm

Re: Building an OSI 502B CPU Board

Post by waltermixxx » Tue Apr 02, 2019 10:31 pm

Thank you for the added details on it, very much appreciated. :) (and the PDF)
Looks like I will either have to take my board to my buddies place who has a vacuum type desoldering station and try and remove the 24 pin socket, or drill a hole in the Augot socket, over the cut, and cut the exposed (hopefully) track. (the 24 pin socket is one of those solid sockets.)

I'm worried about the de-soldering station, as the machined pins will be making contact with the top of the pad it rests on, so I dont think the socket will pop off. grummble grumble. :)
Turning into quite an OSI Junkie (HTFDTH?) Superboard II REV B-40K, 9600b, HC-05 Bluetooth, Superboard II Rev D, C4P rebuild- 502, 542c, 540B. :)

Jeff
Posts: 330
Joined: Fri Mar 07, 2014 4:44 am
Location: British Columbia, Canada

Re: Building an OSI 502B CPU Board

Post by Jeff » Tue Apr 02, 2019 11:56 pm

You could lift the leg of pin 18 out of the socket and tack a jumper to it.

Or build a socket adapter: Plug the eprom into the adaptor, and the adaptor into the U6 socket.
2716 Adaptor1.png
2716 Adaptor1.png (1.55 MiB) Viewed 1882 times
2716 Adaptor2.png
2716 Adaptor2.png (432.09 KiB) Viewed 1882 times
/Jeff
Image

Jeff
Posts: 330
Joined: Fri Mar 07, 2014 4:44 am
Location: British Columbia, Canada

Re: Building an OSI 502B CPU Board

Post by Jeff » Wed Apr 03, 2019 2:11 am

My progress so far.
C488A37A-C4D9-4384-B0A1-A7D33ABB81BE.jpeg
C488A37A-C4D9-4384-B0A1-A7D33ABB81BE.jpeg (617.92 KiB) Viewed 1877 times
/Jeff
Image

waltermixxx
Posts: 118
Joined: Sun Feb 03, 2019 10:31 pm

Re: Building an OSI 502B CPU Board

Post by waltermixxx » Thu Apr 04, 2019 3:38 am

here is my progress thus far, i was able to cut the track under the socket by dremeling out an oval,
and cutting the track. It's not too pretty, but you wont see it with the roms on board. :)

if you prefer I start my own thread on the 502 I can :) sorry to but in, let me know and I will delete this post
:)


IMG_0236.jpeg
IMG_0236.jpeg (1.35 MiB) Viewed 1870 times
IMG_0235.jpeg
IMG_0235.jpeg (770.92 KiB) Viewed 1870 times
Turning into quite an OSI Junkie (HTFDTH?) Superboard II REV B-40K, 9600b, HC-05 Bluetooth, Superboard II Rev D, C4P rebuild- 502, 542c, 540B. :)

Jeff
Posts: 330
Joined: Fri Mar 07, 2014 4:44 am
Location: British Columbia, Canada

Re: Building an OSI 502B CPU Board

Post by Jeff » Thu Apr 04, 2019 5:25 am

It’s all good Walter, feel free to post 😀😃. Makes a more complete story 👍🏻

Well done on the cut trace. Just needs a band-aid now.

/Jeff
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waltermixxx
Posts: 118
Joined: Sun Feb 03, 2019 10:31 pm

Re: Building an OSI 502B CPU Board

Post by waltermixxx » Thu Apr 04, 2019 5:35 pm

As a dentist, i should fill that hole.

But alas I am not a dentist....

perhaps I will even out the hole a bit and then3d print a plug or "filling".

if I do, I will post pics. :)
Turning into quite an OSI Junkie (HTFDTH?) Superboard II REV B-40K, 9600b, HC-05 Bluetooth, Superboard II Rev D, C4P rebuild- 502, 542c, 540B. :)

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