Gigatron – Assembly Part 2

After Part 1 of the Gigatron report dealt with the general introduction and the first steps in setting it up, the second part now includes the completion of the circuit board.

Assembly Part 2

It continues with the IC sockets. According to the instructions, sockets are only intended for the RAM and EPROM. But I decided to socket all ICs - then repairs that may be necessary later are easier (I don't like to solder ICs directly).

Here, too, I proceeded step by step - 4-5 sockets at a time. Unfortunately, I didn't have enough 16-pin precision sockets (25 pieces are required), so I added 10 spring sockets. They like to wear out, but if you don't keep changing the ICs, that should work.

After that, the remaining "small parts" - resistors, resistor networks, audio and 9-pin SUB-D socket - came on the line.

The next thing was about 30 diodes. Two of them lying down, the rest mounted upright. Here, too, the instructions describe the correct orientation in detail: the diode is on the left with a black mark on the top, the wire on the right. Here, too, I assembled in several passes, 5-6 diodes each time with enough space between them so that there is still space for the soldering iron.

At the end there was the 15-pin VGA socket.

To be on the safe side, I checked the voltage again on all sockets - OK, 5.25V everywhere on the correct pins (usually GND "bottom left" and 5V "top right"). Then it was time to insert the ICs. I noticed that I unfortunately soldered a socket the wrong way round (*sic*) - it doesn't matter, since all ICs on the board have the same orientation (either pin 1 on the left or pin 1 on top) the risk is low. The notch on the wrongly oriented socket is hardly noticeable anyway ...

Now it was time to program the EPROM - a 27C1024 (a 1MBit chip, 64kx16Bit). I only got 2 pieces of the OTP version in a hurry, so not UV-erasable. So shouldn't so much go wrong with programming ...

The ROM binaries are available on GitHub - I picked the latest version V5a there. However, it is still beta (and will probably remain so for the time being, since one of the project maintainers unfortunately passed away last year). I will then probably program the second EPROM with the V4. I used my TL866II for programming.

The board, which is now fully equipped, is connected to the monitor, voltage is on, and voila: it works!

Unfortunately, due to the lack of a suitable game controller, I cannot continue testing. An ATARI-like controller does not work because a controller with a serial interface is required for this. Quasi a NES controller. Unfortunately this must have a 9-pin SUB-D interface. It is available as a so-called "Famiclone" controller, but unfortunately only from the USA at high prices. I'm trying to convert a standard NES controller - but I have to order first.

The only thing missing now is the adapter for a PS / 2 keyboard. But I'll save that for the next part.

First of all: it didn't work right away - I'm still troubleshooting ...


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