Saturday, November 24, 2012

MKHBC-8-R1 - half way through soldering expansion bus.

Last weekend I did not finish (as I hoped) soldering of the I/O expansion bus. Today I did some work though and I am half way through it. It did not come out pretty, but it is OK. I hope there will be not too many shorts or no-contacts to correct. See the pictures below.

Bottom of the main board - full view.
The area I worked on today.

All the power, ground and 8 address lines (A0..A7 - a total used in expansion bus) are connected. Remaining connections are data lines, CPU signals and I/O selection signals.

Thanks for accidentally finding and reading this blog 

Marek Karcz

Saturday, November 17, 2012

MKHBC-8-R1 - soldering I/O Expansion Bus.

I advanced the project a bit last night and hope to finish this part over the weekend. The bus will have 4 expansion slots made of IDE sockets. I little more than a half of the pins are used for signals (8 address pins, 8 data pins, CPU bus signals), the rest are ground and one is +5V. I am thinking of changing one of the ground pins to be a 12V pin in case any expansion card needs higher than 5V voltage. The pictures below show the progress I made since last time:

Bottom of the board. The area I work on now is in the middle and on the left. The big mess of wires to the right is the CPU Bus. It looks like that because I had to lift up all excess wire to be able to work on the I/O Expansion Bus. Once I start soldering these wires to the I/O part, the mess will clean up.
Full view of the bottom of the board.
Top of the board - IC and slots layout.

Thanks for looking.

Marek Karcz

Friday, November 16, 2012

MKHBC-8-R1 - preparing to solder I/O Expansion Bus

Just finished, fresh from the oven, schematic for I/O Expansion Bus. I am going to start soldering it into my main board and I hope to finish this weekend. Once I have it, I can assemble CPU board, RAM board and RS-232 card and have a basic computer running.

Marek Karcz

Thursday, November 15, 2012

MKHBC-8-R1 - CPU bus completed.

After a long break (as usual), I did some work on MKHBC-8-R1 again. The progress is slow, project definitely lost a lot of momentum, but don't worry I did not abandon it. In fact, I am about to give it some more time in hope to have some working parts before the end of year.

Today I sort of finished soldering the CPU bus by wiring the remaining +12V line and 8 I/O lines from I/O decoder. About 25% of the back plane or mother board is finished. Remaining (To Do) mother board sections are: I/O Expansion Bus, Prioritized IRQ Controller, Power Supply and Front/Control Panel. And of course the cards that will go into CPU bus and I/O bus sockets. I will start with CPU, RAM and RS-232 cards.

Here is how the mother board looks like now:

The section I soldered today (lower right corner, blue wire).
Quality of connections needs some improvement. My age, crappy soldering iron and lack of soldering rosin (rock) do not help.
View on the entire CPU bus section (down side of the board).
Top of the board (currently still almost empty).
Just another view of the down side of the board.
I can not wait for it to be ready. I have so many plans and ideas for expansions. After CPU/ROM/RAM and RS-232 cards I think I am going to do some sort of mass storage device (CF and/or SD card based) before I proceed to keyboard and Video Controller. BTW - yesterday I purchased on e-bay an unused TI99-4A keyboard. This will be great for my system's console. Mass storage and console (keyboard and video card) are absolute priority - I want MKHBC-8-R1 to be a completely standalone system.

That's it for today. Thanks for reading.

Marek Karcz