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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 🫤
Posted by: DJ68K on 2026-06-06 05:51:44
A bit of new news on this: I have another Performa 520 that's been sitting for several years that I got at VCFMW 2023 without drives or logic board as part of a deal I made with a seller in the parking lot. I figured I'd take it apart, look things over, and decide whether to recap the analog board and have it as a "parts" thing, or perhaps just sell it and the CRT. After I pulled the CRT, I wanted to look at its microphone. To my surprise, there was absolutely zero leakage or corrosion from its capacitors, and the labels on top were different from my previous Performa other than the 4.7.

Since there was no leakage, I easily pulled the caps and measured them in my meter: If they're 4.7uf these are quite out of spec and the ESR/Vloss are terrible. They're definitely on their way out! But given the age and the lousy components used back then, this kind of drift is inevitable. I'm still still not sure of the voltage but given the old parts' small size (higher V parts = larger physical size) and my uneducated assumption there's not much more than 12v going through any part of that circuit, I'll say anything 25v or higher is safe here and they're definitely 4.7uf.

Side note: I wish VCFMW would do a "rebrand" like macOS/iOS/etcOS did recently and forward-date their events by 5 so this year's event would be officially called "VCFMW 26." Or maybe they can host two a year until they catch up? Ah well.
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