Atari ST first model : Q11, R140 and R141 ?

[sporniket]

Hello,

I am almost done placing the components on the reconstruction of the Atari ST board, and the motherboard I own does not provision a place for those 3 components.

2023-08-15--q11-r140-r141.png (317.73 KiB) Viewed 1038 times

I have a clue that they should be above U41 (in the "shifter cage"), as the scanned pcb in the field manual has some traces there. I guess they are on the later revision of the board.

pcb-trace-top--q11-r140-r141-where.jpg (71.99 KiB) Viewed 1038 times

If someone happens to have a PCB with those components (STM) or just on the silk-screen (without modulator), I would appreciate a picture of this part.

Otherwise, I will try as best as I can to infer their positions and orientation.

Thanks in advance.

[exxos]

Have you looked at the MBs here ? viewforum.php?f=53 a lot you can see the numbers of stuff on anyway.

[sporniket]

I thought that I had, but on second visit, I can find some with Q11... thanks...

[sporniket]

So in the end, up to rev E (e.g. viewtopic.php?f=53&t=504) the layout is the same as mine (rev. C), no Q11.

Rev. H (e.g. viewtopic.php?f=53&t=1303) and Rev. I (e.g. viewtopic.php?f=53&t=2004) have Q11, but this part of the circuit has been heavily reworked anyway, meaning a handful of components numbers does not match my schematic and the original schematic . So I just followed traces and placed components as best as I could.

I am curious to see this part on a rev. F and G.

Anyway, the placement is done, and I will rework the traces that do not match when there will be discrepancies.