Sporniket's log on hardware stuff

[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...

[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

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.

[exxos]

No big deal anyway :). Glad you're doing away with those right angles at least :thumbup:

[sporniket]

Glad you're doing away with those right angles at least :thumbup:

At least one thing that I'm doing right :)

[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

Anyway, the front side is done.

2021-08-12--front-side-is-done.jpg

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).

[DoG]

Well done! Looks really nice.

[sporniket]

Yes, it is very satisfying in itself :)

[sporniket]

The back side now.

2021-08-12--back-side-is-done.jpg

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

2021-08-12--drc-not-so-bad.jpg

[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--02.jpg

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

2021-08-13--03.jpg

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

Then I prepared to for testing...

2021-08-13--05.jpg

... 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.

[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)

kicad-conversions--atari-ste-motherboard--c300780-001--v1.0.0.rc4-F_SilkS.pdf

kicad-conversions--atari-ste-motherboard--c300780-001--v1.0.0.rc4.pdf

07--pcb-raytrace-south-west.jpg