Another Gigatron TTL in Finland

A place to eternalise your Gigatron build photos. From box to BASIC.
Forum rules
Use this forum to show off your build photos. For build issues, please consult the directions in the sticky post on top instead.
veekoo
Posts: 121
Joined: 07 Jun 2021, 07:07

Re: Another Gigatron TTL in Finland

Post by veekoo »

The non-working project. I have put good effort try to fix this, but no function yet. Last try will be use troubleshooting.xlsx to find where faults occur.
Attachments
90D72EFE-2489-4AA2-BD10-EA0639DE876D.jpeg
90D72EFE-2489-4AA2-BD10-EA0639DE876D.jpeg (4.67 MiB) Viewed 3926 times
veekoo
Posts: 121
Joined: 07 Jun 2021, 07:07

Re: Another Gigatron TTL in Finland

Post by veekoo »

New case for Gigatron TTL from acrylic
Attachments
128BC030-4635-47E9-9E1E-7DD0E3E0CB9C.jpeg
128BC030-4635-47E9-9E1E-7DD0E3E0CB9C.jpeg (4.07 MiB) Viewed 3913 times
veekoo
Posts: 121
Joined: 07 Jun 2021, 07:07

Re: Another Gigatron TTL in Finland

Post by veekoo »

I had troubles with the usb power connector. The cable tends to bend the connector and after a while it became loose. Now it flickers the power and is not useable. Some soldering fixed it.
Sugarplum
Posts: 94
Joined: 30 Sep 2020, 22:19

Re: Another Gigatron TTL in Finland

Post by Sugarplum »

veekoo wrote: 17 Jul 2021, 16:36 I had to try to make a DIY kit from budgetronics. Lack of skills probably didn't get it all working so ended up using it as spare.

I ordered second one "Fully Assembled Gigatron TTL" from ebay and got it at reasonable price. When it arrived it was missing U39 serial input IC and another mail was coming with 74HCT595 later on.

Well I had the spare parts and took SN74HC595N, I was able to get blinkenlights, power on led, startup sound and main screen booting.

Long story short I had 3 keyboards at what 2 seemed compatible with PS/2 standard and I tried them but nothing happend. No signal lights at keyboard otherwise system seemed ready to accept commands.

Seller said it seemed normal operation because of missing the right IC chip and my chip needed 1N60P diodes and the board had BAT42 instead. Actually diodes looked pretty much the same as in my failed pcb.

Probably in question is some signal level matching or timings what I understood. Seller seemed sure of things so I have meen mostly waiting customs to send me my letter.
The BAT42 diodes are fine, only faster. It is possible that the resistor packs near the diodes are lower in values too. The diodes (and resistors) shouldn't affect the keyboard. The keyboard not working shouldn't be normal since you did indeed replace the missing shift register. So maybe you weren't getting enough power, or maybe the shift register you got from the first machine was bad.

One possible thing to check would be the phone charger you are using. If the assembled Gigatron has been modified to be able to run at a higher speed, it would require more power. So 100 mA or so more than what you have might make a difference.

Edit: Okay, so you fixed the issue on the mostly working one, and it sounds like a subtle incompatibility with the shift register. Glad you were able to get it to work. The "dead pixels" could be the ROM version.
veekoo
Posts: 121
Joined: 07 Jun 2021, 07:07

Re: Another Gigatron TTL in Finland

Post by veekoo »

I waited for couple of months before changing to solid ROMv6. Found empty desk where to put retro gear

I also went to GLCC 2.3 and compiled all my C-programs to it. Everything seems to be working as usual.
Attachments
IMG_1282.jpg
IMG_1282.jpg (2.74 MiB) Viewed 2305 times
IMG_1280.jpg
IMG_1280.jpg (2.59 MiB) Viewed 2305 times
monsonite
Posts: 101
Joined: 17 May 2018, 07:17

Re: Another Gigatron TTL in Finland

Post by monsonite »

Good Work!

I like the purple PCB.

With a bit of work a Gigatron can be pushed to 10MHz clock, or 12.5MHz with swapping some of the ICs for 74F (fast) series).

Whilst I personally have little need for low resolution colour graphics and sound,the Gigatron is a remarkably versatile and fast CPU, capable of emulating many of the classic 8-bit cpus from the 1970s, or providing a reasonably quick 16-bit virtual machine.
Post Reply