My Gigatron build

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.
cde
Posts: 11
Joined: 13 Sep 2020, 08:37

My Gigatron build

Post by cde »

This build is based on the kit from BudgeTronics with the addition of:
- low-profile DIL turned pin sockets for easier replacement of chips and attachment of logic probes
(I noticed afterwards that two chips are 14-pin and not 16-pin. So I had to cut off the legs of two 16-pin sockets to make it work).
- black 40-pin ZIF socket with small pins (ARIES 40-6554-10)
- rubber pads on the underside to increase height (necessary to plug in Pluggy McPlugFace)

I've also bought a TL866II+, EPROM eraser and a few AT27C1024 for easier reprogramming.

The board worked on the first try after powering up which was quite satifying! :-)

20200915_220320.jpg
20200915_220320.jpg (3.67 MiB) Viewed 6792 times
20200915_220302.jpg
20200915_220302.jpg (4.44 MiB) Viewed 6792 times
20200915_220440.jpg
20200915_220440.jpg (2.52 MiB) Viewed 6792 times
Last edited by cde on 15 Sep 2020, 21:17, edited 1 time in total.
bmwtcu
Posts: 145
Joined: 01 Nov 2018, 12:02

Re: My Gigatron build

Post by bmwtcu »

I gotta say, that black PCB looks really sharp!
walter
Site Admin
Posts: 159
Joined: 13 May 2018, 08:00

Re: My Gigatron build

Post by walter »

The first picture I see of a built Budgetronic Gigatron. Thanks for sharing!
cde
Posts: 11
Joined: 13 Sep 2020, 08:37

Re: My Gigatron build

Post by cde »

Thanks Walter! By the way I just tested the Tetronis demo and the music seems really strange, much too high pitched. Then I tried Tetronis in the emulator, and heard the music as it should be. I had a look at the audio DAC with a multimeter and measures 10 KOhm for pins 2 3 4 5 but 5 KOhm for pin 6. Is this to be expected? Please have a look at the following video: https://imgur.com/a/T3ilK2p (note that by default, sound is muted).
Last edited by cde on 16 Sep 2020, 13:27, edited 1 time in total.
walter
Site Admin
Posts: 159
Joined: 13 May 2018, 08:00

Re: My Gigatron build

Post by walter »

I hope you understand, but I cannot give support on Gigatrons bought elsewhere..
cde
Posts: 11
Joined: 13 Sep 2020, 08:37

Re: My Gigatron build

Post by cde »

Right, well anyway Budgetronics messed up and they provided an incorrect part for the DAC. They have provided a 6X-1-103LF, which is a simple resistor network whereas the correct part is the 4606X-R2R-103LF. Interestingly the 4606X-R2R-103LF is pretty rare and out of stock until at least december. Instead I found a 10-pin R2R 10K network on eBay which I believe will work by cutting off the extra 4 pins (7-10).
cde
Posts: 11
Joined: 13 Sep 2020, 08:37

Re: My Gigatron build

Post by cde »

As I suspected it was indeed the DAC at fault. I desoldered the invalid part and replaced it with a resistor ladder I made based on the schematics and now the Tetronis music sounds as it should.

For reference, music with invalid DAC part: https://imgur.com/a/T3ilK2p
Gigatron with proper resistor-ladder DAC: https://imgur.com/a/YXwUHhN
(note that imgur mutes videos by default)

Here's a closeup of the ladder:

ladder.png
ladder.png (975.56 KiB) Viewed 6736 times
bmwtcu
Posts: 145
Joined: 01 Nov 2018, 12:02

Re: My Gigatron build

Post by bmwtcu »

cde wrote: 16 Sep 2020, 13:23 ... I found a 10-pin R2R 10K network on eBay which I believe will work by cutting off the extra 4 pins (7-10).
I suspect that won't work since the last 2 pins are wired differently from the rest of the SIP. I also built one a while back out of discrete SMT resistors because I couldn't think of a better solution at that time.
Attachments
Capturer2r.JPG
Capturer2r.JPG (20.37 KiB) Viewed 6707 times
cde
Posts: 11
Joined: 13 Sep 2020, 08:37

Re: My Gigatron build

Post by cde »

Thanks, you're probably right. Anyway I have contacted Budgetronics and they have found a temporary solution for other Gigatron purchasers: they will provide a ladder based on discrete resistors (in a more compact fashion than mine), until the needed component gets back in stock.
cde
Posts: 11
Joined: 13 Sep 2020, 08:37

Re: My Gigatron build

Post by cde »

bmwtcu wrote: 17 Sep 2020, 10:44
cde wrote: 16 Sep 2020, 13:23 ... I found a 10-pin R2R 10K network on eBay which I believe will work by cutting off the extra 4 pins (7-10).
I suspect that won't work since the last 2 pins are wired differently from the rest of the SIP. I also built one a while back out of discrete SMT resistors because I couldn't think of a better solution at that time.
I've just tested the modified 4310R-R2R-103LF with last 4 legs cut. The last resistor is indeed a bit off (60 Ohm instead of 50), but it nonetheless sounds fine to me: https://imgur.com/a/fEG4gnS

In the video above you can also see the ladder kindly sent by Budgetronics who I thank for their quick response (it is the ladder with yellow plastic and the first pin marked by a black dot).
Post Reply