I got an Amiga 1200 off ebay and it works great, board looks perfect, no leakage, no bad traces, nothing, and yet I have this mysterious mod I've never seen before. Does anyone know what it is?

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I believe it is to clean the weak CCK clock signal coming from Alice to Budgie.

PCB rev 1.d4 and 2b should have this.

It is on the R2 schematic (http://www.amigawiki.de/dnl/schematics/A1200_R2.pdf) - search for "BUDGIE BLUES" and check pin 36 (CCK).

I think U37 ("TI 231 JFA HC08" in your photo) is a quad positive-or (74F32 / SN74S32) which is serving as the buffer.

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    Are you able to explain what that's for? in other words why should a clock be cleaned
    – OmarL
    Jun 8 '19 at 19:51
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    @Wilson because the clock signal was marginal due to poor layout, high fanout, incorrectly specced / manufactured driver, etc. Clock buffering is a standard part of digital design, this after-the-fact rework was needed because the required buffer here was overlooked / omittted during initial design. Jun 8 '19 at 20:18

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