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Hi Phil, Definitely, if you can convert the board you already made into DXF, I can turn it into a set of gerbers and have it made. For new efforts, I was hoping there might be a way to automate the process; for example, use photoshop to accentuate the traces, then turn into a black & white image, to...

Looks like I was writing my last post while you were writing yours. Actually, So the problem is in the timing chain. The stuck low CLR line is a problem. That will inhibit the whole column timing counter chain. The END_BLANK signal develops as part of that chain, so it's likely a symptom but not the...

Hi Philip, I do agree that from the diagram, there should be pulsed waveforms at the base and collector of that transistor, if the base is going from 0 to 1V or so. Perhaps that is a problem. I have not worked on the 540B cards, but I think they're pretty similar to the 540A B&W cards. From my exper...

Thanks for the advice in the Xtal. I went to replace the Xtal today and realized that I had left the machine on for the past 10 hours or so. Unfortunately there is nothing to indicate wether it's on or off except for the position of the switch. Anyway, the video bored now displays nothing, were as ...

You must be pretty decent at circuits. You seem quite comfortable jumping in and repairing these old machines. I hope the logic is sound :-) I didn't really change the logic, so hopefully it will work out. Since I was unable to break out the machine to test it on, I am relying somewhat on faith. How...

One last question. Unfortunately the cable with the 40 pin headers coming off the 505 bored was removed before shipping the computer, and the headers were crushed in transit, with legs falling off and is totally unusable. Does anyone know where I can get a replacement cable? I recently ordered some...

Latest cleanups and routing posted here . Out of laziness, I used two ground planes, laid the 5V circuit, connected up the floppy connectors, and then invoked the auto router, which did did get 100% routing, but REALLY ugly. Many of the tracks were acceptable, if convoluted, so I cleaned up the rest...

12MHz should work fine. CRT's are pretty forgiving on slight timing differences. I have two 540B cards, with 11.765 and 12.0 MHz crystals. Good luck with the restoration. Please continue to keep us posted. If you have some pics, feel free to post them here in the thread!

Best regards,

Dave

That's very cool. I've never seen one of those boards, other than on Mark's web site. It would be awesome if you posted some pics in this thread before and after, if you decide to add the extra sockets.

Whoops, 0 for 2 on the Uploads last week. Fixed.