Re: Bad Volume Control on a //c

["Roger Johnstone" <rojaws@mac.com>]

In article <Pine.GSO.4.33.0109241821300.12626-100000@gere.odin.pdx.edu>, 
Aaron Heiss <heiss@deletethis.pdx.edu> wrote:

> I have an Apple //c (my main computer now, actually) that was given to me
> seven years ago by someone who found it in an attic, where it probably sat
> for a good few years prior.  Its volume knob has never worked properly for
> me.  If it is set to anything over about two-thirds maximum, the speaker
> works flawlessly (and it's *loud*!); if it's set in the bottom third of
> its range, no sound is produced at all.  In between it sometimes works and
> sometimes doesn't, but usually can be persuaded to make noise if the knob
> is physically wiggled by pushing it.
>
> I assume the machine's history that this problem is due to dust in the
> potentiometer.  I have taken the machine apart and cleaned it thoroughly
> (something I do with all new computer acquisitions)  to no avail; I have
> tried spraying "canned air" at it when it was apart, and have noticed no
> result from that either.  The only thing that I have not done yet is to
> remove the motherboard from the bottom case half, which might help with
> access with the canned air, but which does not look trivial.
>
> Has anybody else any experience with this sort of problem?  Is there some
> trick to getting dust out of awkwardly placed potentiometers?  Is it
> possible that this is not a dust problem in the first place?  I'd rather
> not have to take out and resolder the knob to clean it properly or to
> replace it (though I could if I had to), so I'm asking here first.  I'd
> appreciate any tips that could be passed my way.
>
> Thanks in advance!
>
>
> Aaron Heiss

Old pots can get a build up of dirt on the track and a tarnished wiper,
blowing air into it probably wont have any effect. The best way to clean it
is with a can of contact cleaner, which should be available from any
electronics shop or electrical trade shop. It's a light oil especially made
for cleaning electrical contacts. We go through a can of it every two months
where I work! Just spray it liberally into the pot, most of it will
evaporate but it will leave a thin film behind, so avoid getting it on
anything else. Wiggle the control back and forth for a minute and it should
come right. If it doesn't work then the pot is probably worn out and would
need replaced.

--
Roger Johnstone, Invercargill, New Zealand

Apple II - Future Cop:LAPD - iMac Voodoo2 - Warcraft II
http://homepage.mac.com/rojaws
______________________________________________________________________

My software never has bugs. It just develops random features.