Building up a 540B video board

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

Building up a 540B video board

Post by Jeff » Tue Mar 12, 2019 12:17 am

Hi All,

I am planning on building a Replica 540 rev B video card.

Does anyone know where I can get the 2 crystals?

X1 is listed as 12.08 Mhz and X2 is listed at 5.579545 Mhz.

/Jeff
Last edited by Jeff on Wed Sep 04, 2019 1:55 am, edited 1 time in total.
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waltermixxx
Posts: 118
Joined: Sun Feb 03, 2019 10:31 pm

Re: Building up a 540 rev B

Post by waltermixxx » Sat Mar 23, 2019 2:30 pm

I'm building one too. :)
so if anyone knows...

pass it on....

actually that might be a typo, i think it should b e 3.579xxx standard colour burst crystal.....
those are available pretty much everywhere.... I wonder if a good old fasioned 12 mhz crystal will work...

this is from the C4P service manual:
crystal parts list.png
crystal parts list.png (202.08 KiB) Viewed 1839 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 up a 540 rev B

Post by Jeff » Wed Apr 03, 2019 2:13 am

The character generator will need to be a 2716 EPROM, so a trace cut and a jumper will be needed.

I created a layout that illustrates the needed mod.
540B 2716 Chargen Mod.png
540B 2716 Chargen Mod.png (440.98 KiB) Viewed 1751 times

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

Re: Building up a 540 rev B

Post by waltermixxx » Thu Apr 04, 2019 5:39 pm

Thank you :)
this will be very very helpful :)

Cheers.
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 up a 540 rev B

Post by Jeff » Fri Apr 26, 2019 10:14 pm

Progress so far...
540B.jpg
540B.jpg (485.79 KiB) Viewed 1517 times
/Jeff
Image

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

Re: Building up a 540 rev B

Post by Jeff » Fri Aug 23, 2019 12:07 am

Finally all the IC's arrived from China and I had some time to populate it.
540.jpg
540.jpg (1.36 MiB) Viewed 698 times
/Jeff
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Jeff
Posts: 330
Joined: Fri Mar 07, 2014 4:44 am
Location: British Columbia, Canada

Re: Building up a 540 rev B

Post by Jeff » Mon Aug 26, 2019 12:25 am

While getting the board to operate, I discovered that R22 (10K Pot) should not be installed, and simply jumpered.

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

Re: Building up a 540 rev B

Post by waltermixxx » Mon Aug 26, 2019 8:09 pm

you got video?
can we see? he he :) (just excited not dubious)

I will have to start working on this board once we complete the colour board Steve Gray is working on.
we have yet to meet up and play :) we are going to do it together, Steve, Josh and I. :)

Cheers. :)
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 up a 540 rev B

Post by Jeff » Fri Aug 30, 2019 11:03 pm

I have a screen full of random characters.

The board is not yet responding to instructions from the 502 CPU board.

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

Re: Building up a 540 rev B

Post by Jeff » Tue Sep 03, 2019 9:13 pm

The board is now displaying characters from the 502 board, (as opposed to garbage). The video is shaky and color isn't working yet, but at least *most* of it is working.

There were several changes needed to make the board match the schematic. All these changes apply to the original OSI PCB... and the replica faithfully reproduced them, so they need to be applied.
1: Missing trace: Just below C20, on bottom, add small jumper (just above pin 1 of U4H)
2: Missing trace: Add jumper from U4J pin 1 to U4J pin 4
3: Wrong trace: On the top of the board, cut the trace that leads to U4H pin 5. (This cut removes /02VMA signal from the pin, which should be S1)
4: Missing trace: Add jumper on bottom from U4H pin 5 to U4J pin 3 (use VIA next to U4I pin 5) This adds the S1 signal to that pin.

Here is a diagram of those fixes.
Required Mods.png
Required Mods.png (451.18 KiB) Viewed 328 times
I tracked down the issue of it not working at all to a missing resistor on the 502 board. Read this topic for details. viewtopic.php?f=3&t=503
VMA Schematics.png
VMA Schematics.png (1.6 MiB) Viewed 328 times
I am in the process of documenting my adventure and I will post it here when done.

/Jeff
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