The logic board of the iMac (27-inch, Late 2009), model A1312, 2009, 27-inch, Core 2 Duo. Known faults are being collected.
No guided tree is live for this board yet. The profile, the viewer and manual entry are there on the free plan, and the first sessions on it build the tree.
Checked on 2026-10-29 against 2 sources: verified. iFixit answer and an eBay.de listing (both seen in search results) identify 820-2507-A as the Late 2009 27-inch A1312 Core 2 Duo 3.06 GHz board (EMC 2309); EveryMac gives that configuration as iMac10,1 (MB952LL/A). The Late 2009 27-inch Core i5/i7 uses a different board, 820-2733 (iMac11,1). Consistency review: variant extended from '27-inch' to '27-inch, Core 2 Duo' (taken from the notes above) so this row is distinguishable from 820-2733, which carries the same model name, A-number and year but is the Core i5/i7 machine (iMac11,1). Revision A is a placeholder until Studio records the real revisions.
Open the board in NextProbe, answer the symptom questions and follow the lit point. The free plan includes three guided sessions a month. Your own boardview and schematic stay on your machine.