68kMLA Classic Interface

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Performa 5xx Microphone Capacitors
Posted by: DJ68K on 2026-05-15 10:52:55
I'm working through a full restoration of a Performa 550 w/ Apple IIe card and it has this microphone board (820-0388) with two leaky capacitors. I'm not sure if these are 33u or 4.7u capacitors (tempted to believe they're 4.7u and the 33 is the series or something like that). I can try to desolder and measure them but I don't have much luck desoldering corroded SMD caps off the board; I prefer the twist-off method. I searched through here a bit and didn't find a thread where someone was asking about them.

photo_2026-05-15_12-46-16.jpg
Posted by: obsolete on 2026-05-15 10:55:19
Yikes, that's crusty! I agree that those are likely 4.7uF.
Posted by: DJ68K on 2026-05-15 12:09:12
Sounds good to me! Decapped, cleaned, neutralized, recapped, and coated. Time to get the rest of it cleaned up & reassembled. Thanks!photo_2026-05-15_14-07-44.jpg
Posted by: obsolete on 2026-05-15 13:13:58
Nice work! I wonder whether the reason that nobody else has posted about these caps is that the vast majority of 5xx owners are afraid to disassemble their fragile, brittle machine far enough to reach this board 🫤
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