Editing Atari 520ST (section)

== PCB Schematics & Service Guide ==
Motherboard families and identifying service references commonly seen on 520ST/520STM:
{| class="wikitable"
! Assembly / PBA !! Typical models !! Revisions seen !! Notable identifiers / notes
|-
| C070115 || 260/520ST (very early) || Rev. 2 || Earliest 520ST board reported; footprints for 2‑ROM boot TOS and 6‑ROM 192 KB TOS; minimal EMI chokes.<ref>{{cite web |url=https://forums.atariage.com/topic/319794-almost-unknown-atari-st-schematics/ |title=(Almost) Unknown Atari ST schematics |publisher=AtariAge Forums |date=2021-04-27 |access-date=2025-08-13}}</ref>
|-
| C070231 || 260/520ST || — || Factory schematics drawing C070112 (Atari Japan); full community KiCad reconstruction available for repair work.<ref>{{cite web |url=https://archive.org/details/Atari_520ST_Schematic_1985 |title=Atari 520ST Schematic (1985), drawing set |publisher=Internet Archive |access-date=2025-08-13}}</ref><ref>{{cite web |url=https://forums.atariage.com/topic/367081-conversion-of-the-schematics-of-the-atari-260520st-motherboard-into-kicad/ |title=KiCad conversion of Atari 260/520ST C070231 |publisher=AtariAge Forums |date=2024-05-25 |access-date=2025-08-13}}</ref>
|-
| C070243 || 520ST/520STM || Rev. C, H, I || Later short‑case boards; added numerous EMI chokes vs. C070115; common target for 1–4 MB RAM mods.<ref>{{cite web |url=https://retrocomputing.stackexchange.com/questions/21618/why-do-some-atari-st-motherboards-include-many-inductors |title=Why do some Atari ST motherboards include many inductors? |publisher=Retrocomputing StackExchange |access-date=2025-08-13}}</ref><ref>{{cite web |url=https://wiki.console5.com/wiki/Atari_ST |title=Atari ST recap notes by board (C070243 Rev C/H) |publisher=Console5 TechWiki |access-date=2025-08-13}}</ref>
|}
Service/schematic references
* Early factory schematics: “Atari (Japan) Corporation” drawing C070112 (1985) covering 260/520ST main logic; scans circulate online.<ref>{{cite web |url=https://archive.org/details/Atari_520ST_Schematic_1985 |title=Atari 520ST Schematic (1985) |publisher=Internet Archive |access-date=2025-08-13}}</ref>
* [[Atari 520STE/1040STE Field Service Manual|520/1040STE Field Service Manual]] (C302481‑001 Rev A, Aug 1991) includes many circuits compatible in concept (MFP, YM2149, DMA, WD1772) and is frequently referenced for troubleshooting I/O sections shared with ST family.<ref>{{cite web |url=https://www.manualslib.com/manual/2170364/Atari-520ste.html |title=Atari STe 520/1040 Field Service Manual, C302481‑001 |publisher=ManualsLib |date=1991 |access-date=2025-08-13}}</ref>