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From: Andrew Roughan <no_email@invalid.invalid>
Newsgroups: comp.sys.apple2
Subject: Re: Magic smoke!
Date: Tue, 3 Sep 2024 23:32:20 -0000 (UTC)
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Scott Alfter <scott@alfter.diespammersdie.us> wrote:
> In article <dog_cow-1725052556@macgui.com>,
> D Finnigan  <dog_cow@macgui.com> wrote:
>> phigan wrote:
>>> On 2024-08-26, D Finnigan <dog_cow@macgui.com> wrote:
>>>> 
>>>> if I have an extra capacitor. I think the last machine I had to replace was
>>>> a Mac 512K. I may have ordered an extra then. 
>>> 
>>> Are there some known people or places that one can send Apple2 and
>>> classic Macintosh units to for re-capping?
>> 
>> The Apple II isn't notorious for failing capacitors (except for this one in
>> the power supply!), so I don't know of any services for this kind of work.
>> I have heard of places for older Macintosh models, but I haven't used any of
>> them. There were some people selling capacitor kits for Macs too, which
>> could save some time as long as you did the work yourself.
> 
> I can think of only two classes of devices where recapping is likely to fix
> a problem:
> 
> 1) Computer equipment (and maybe other electronics more generally) of a
>    certain age that was built with counterfeit electrolytic capacitors
>    that tended to bulge, leak, and fail:
> 
>    https://en.wikipedia.org/wiki/Capacitor_plague
> 
>    Apple IIs (and 68K Macs, while we're at it) predate this issue by several 
>    years.
> 
> 2) Really old devices (mostly running on vacuum tubes instead of solid-state
>    devices) that used wax- or plastic-covered paper capacitors in which
>    failure of the wax covering would cause the paper dielectric to absorb
>    moisture, altering its properties.
> 

The Wikipedia article you cited acknowledges there are other causes for
capacitors to fail than counterfeit electrolyte.
One being that they can dry out over time.

I stored a IIgs keyboard in my roof space (which gets hot in summer) and it
didn’t work after several years. After a lot of troubleshooting and getting
nowhere the caps were replaced as a what-if and it now works.

Regards
Andrew