Bun's Lab – Telegram
Bun's Lab
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Electronics projects, vintæg computing, programming and repairs. A minimalist blog of sorts.
@BunsGarden @BunsNook
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Look at that jank. It's a miracle this place hasn't burnt down yet.
The difference a 287 makes
15 min repair: llämp. Power transistors were fine, so were the diodes and the driver transistor. In the end it was a broken primary on the output transformer, luckily right at the connection.
If you know you know.

These are in Macintosh II, leak and destroy those computers. This particular one destroyed a IIfx.
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Ok I'm bummed out now. My 286 broke. This one:
Three out of three dead octek boards with Headland chipset. Although I think on this it's a mechanical issue. It broke after handling it to try the 287.
Bun's Lab
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HT12.pdf
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I don't believe it. There is actually a datasheet for this chipset.
I found out what killed the 286. A floating protective earth. Same issue as in the kitchen
Lovely
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Next thing on the bench: another 286 board.
I've already replaced a bunch of 74F244 buffers and 74F245 bi-directional bus transcievers because they had wonky looking outputs or even inputs