Sporniket's log on hardware stuff

Blogs & guides and tales of woo by forum members.
User avatar
exxos
Site Admin
Site Admin
Posts: 23496
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Sporniket's log on hardware stuff

Post by exxos »

So how close is the routing to the original STE ? I'm thinking maybe it could be seen exactly how Atari did the grounding around the DMA to CPU areas...
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
sporniket
Posts: 956
Joined: Sat Sep 26, 2020 9:12 pm
Location: France
Contact:

Re: Sporniket's log on hardware stuff

Post by sporniket »

@exxos , for all traces except grounding, I try to keep the same relative position between traces and components. Meaning if trace A goes between B and C on the real mother board, it will be the same on the motherboard, 90% of the time.

A picture to illustrate, here is a close up of the component side around the GSTMCU, and the result of my work :

2021-08-10--spot-the-difference.jpg
2021-08-10--spot-the-difference.jpg (297.86 KiB) Viewed 2960 times

So you will get a rough idea of through which area a signal goes between CPU and DMA, but I don't know if it will be of help to you. I am quite sure that if someone make a build from my PCB, it will be mostly luck that it works. At least there should be no short.

For the grounding I am cheating with 2 inner ground planes. On the real motherboard, I can see that any unoccupied space of the board constitute grounding.
User avatar
exxos
Site Admin
Site Admin
Posts: 23496
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Sporniket's log on hardware stuff

Post by exxos »

No big deal anyway :). Glad you're doing away with those right angles at least :thumbup:
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
sporniket
Posts: 956
Joined: Sat Sep 26, 2020 9:12 pm
Location: France
Contact:

Re: Sporniket's log on hardware stuff

Post by sporniket »

exxos wrote: Tue Aug 10, 2021 7:54 pm Glad you're doing away with those right angles at least :thumbup:
At least one thing that I'm doing right :)
User avatar
sporniket
Posts: 956
Joined: Sat Sep 26, 2020 9:12 pm
Location: France
Contact:

Re: Sporniket's log on hardware stuff

Post by sporniket »

The routes are all done, now I am working on the copper fillings, meaning also the separation of analog parts. There are 2 analog areas, the sound and the video. Like the traces, I loosely follows what I see on my motherboard.

I left some disclaimers on the silkscreen...

2021-08-12--disclaimer.jpg
2021-08-12--disclaimer.jpg (71.74 KiB) Viewed 2928 times

Anyway, the front side is done.

2021-08-12--front-side-is-done.jpg
2021-08-12--front-side-is-done.jpg (390.15 KiB) Viewed 2928 times

I hope to make a new release candidate by next week. Then I plan to add comments about some fixes that would be helpfull and their references ( #mandatoryFixes :D ).

Anyway, doing a complete PCB proved to be a valuable tool to proofread my schematics.

edit : the github repository is up to date, as usual. (see my signature for the repo).
User avatar
DoG
Posts: 1125
Joined: Sat Apr 07, 2018 12:26 pm

Re: Sporniket's log on hardware stuff

Post by DoG »

Well done! Looks really nice.
User avatar
sporniket
Posts: 956
Joined: Sat Sep 26, 2020 9:12 pm
Location: France
Contact:

Re: Sporniket's log on hardware stuff

Post by sporniket »

The back side now.

2021-08-12--back-side-is-done.jpg
2021-08-12--back-side-is-done.jpg (330.05 KiB) Viewed 2896 times

Now it's time to tidying things before release...

2021-08-12--drc-not-so-bad.jpg
2021-08-12--drc-not-so-bad.jpg (171.09 KiB) Viewed 2896 times
User avatar
sporniket
Posts: 956
Joined: Sat Sep 26, 2020 9:12 pm
Location: France
Contact:

Re: Sporniket's log on hardware stuff

Post by sporniket »

Today I am working on the Lynx 2 that is still running, but with a screen too bright and around 7V at C41, and non working off-on, the only way to put-remove batteries.

Before that, I assembled a battery holders for easier testing when the console is opened :

2021-08-13--01.jpg
2021-08-13--01.jpg (51.77 KiB) Viewed 2883 times
2021-08-13--02.jpg
2021-08-13--02.jpg (52.04 KiB) Viewed 2883 times

Now, back on this "still running Lynx", I had noticed a suspicious bodge wire :

2021-08-13--03.jpg
2021-08-13--03.jpg (76.33 KiB) Viewed 2883 times

It turns out that it is a mode using the headphone pins to bypass the voltage regulator circuitry, so I removed it -and reflowed the solder joints-.

Side note : I can now compare non-leaded vs leaded solder handling, and now I understand all the frustration I read here and there regarding non-leaded solder. With leaded solder, I became magically good at soldering, and at using the solder wick. I guess that my faithful 25W-entry-level soldering iron and its pointy tips, while totally suitable for leaded solder, are barely suitable for non-leaded soldering (especially on pads connected to ground or large copper areas...)

2021-08-13--04.jpg
2021-08-13--04.jpg (79.65 KiB) Viewed 2883 times

Then I prepared to for testing...

2021-08-13--05.jpg
2021-08-13--05.jpg (77.5 KiB) Viewed 2883 times

... And nothing happens :( . A close look at the mother board, I can see that it is brownish around Q8, so next time I can make an order to mouser, I will try to replace that transistor.
User avatar
sporniket
Posts: 956
Joined: Sat Sep 26, 2020 9:12 pm
Location: France
Contact:

Re: Sporniket's log on hardware stuff

Post by sporniket »

The last -hopefully- release candidate before the real one.

https://github.com/sporniket/kicad-conv ... /1.0.0.rc4

This release includes :
  • A standalone Kicad project (all custom libraries included and ready to use)
  • A PDF of the schematics
  • A PDF of the silkscreen
  • A small gallery
The schematics seems complete and free of errors, thanks to making the pcb. I also mentionned some hardware fixes (with related urls), only related to the schematics and "easily" doable (changing a soldered PLCC CPU is not "easy" for me) :
  • DMA pull-up on databus (done on the floppy disc controller U301)
  • WD1772 pull-ups (done on U305)
  • LMC audio mix fix (done near U508)
  • RGB Video ghosting fix (done at C411)

07--pcb-raytrace-south-west.jpg
07--pcb-raytrace-south-west.jpg (309.97 KiB) Viewed 2850 times
Post Reply

Return to “MEMBER BLOGS”