Assembling an Apple-1 computer – Part 3

It’s Alive!

My Apple-1 is up and running. I’m still short one of the transformers so I used one of my triple output bench power supplies to provide the +10VDC and +/-16VDC by tying directly to the filter caps.

I built out the video cable per the original Apple-1 manual and plugged it into the 30+ year old monitor I have.

I stuffed out the parts required to drive the video stream, checked the parts several times and hit the power. I had video, the ‘@’s are blinking as expected. When jumping the ‘Clear’ input to +5VDC the screen clears with a single ‘@’ blinking in the upper left corner.

Next I stuffed out the parts for the CPU group, placing a solder bridge on the jumper points for 6502, no DMA, and the chip selects for the 4K DRAM. Again I checked every part for orientation, bent pins, correct part in the socket etc.

I powered up and again got the random start up screen with the ‘@’s blinking. I jumped ‘Clear’ and the screen cleared. I then jumped ‘Reset’ to VSS and the CPU group reset. The video acted correctly when reset with an active CPU displaying:

 

\
@

The fact that the ‘@’ sign is below the ‘\’ and not along side it is the indication the CPU group is running, this is how subtle these old machines are.

“It’s Alive” was exclaimed loudly as I sat back and smiled.

I still have a lot of work left to finish this project.

• Install the additional 4K of DRAM so I can run Apple Basic
• Jumper the board for the additional 4K
• Create an adapter for the parallel ASCII keyboard I have
• Build out the cassette interface so I can save/load programs
• Build some kind of case for it

The project list grows…….

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