17 May
2010
17 May
'10
5:42 p.m.
Date: Mon, 17 May 2010 11:02:56 -0500
From: Mark Tapley <mtapley at swri.edu>
First pass, no sound out. Not speaker, not headphone
connector. Wait, if you hold your ear right up against it, you hear a
*little* bit. Hm.
This is a (uhm) classic symptom of leaking caps on the Classic, and
Classic II, and SE/30, and IIci, etc.
We regularly discuss this issue (these days we usually just reference old
threads) over on 68kmla.net. A search on "tantalum" is probably best, as
the typical replacements we use are tantalums of the proper size and
values.
gunge, and they were centered on the three groups of
what look like
my favorite nemesis .... capacitors!
<gnashing of teeth>
Many q-tips and much isopropanol later, it boots, but it's
still quiet - too quiet - and I have a bad feeling about how long
it'll keep running before I have to clean it again. There's a bit of
corrosion on one lead of the sound chip, but I can still hear a very
very faint edition of the sound it's supposed to make.
2) If (sigh. When) I have to pull those things off, I will need a
hot-air soldering station, correct? My thought is, cut up an aluminum
can to make an air dam isolating the cap. from the rest of the board,
then blast it with hot air until it flies off or vaporizes. Is that
close to right?
Use two pencils simultaneously. Radio Shack sells a 15 watt grounded
pencil with a fine tip for less than $10. If you use two pencils you're
much less likely to lift a pad by prying on a cap while heating one side,
and after the other side has already cooled.
If you were to use hot air, I find that modeling clay works conveniently
and well to protect other components on the board.
The simple procedure is:
1) Remove the old caps and remove the solder on the pads.
2) Clean the board thoroughly.
3) Replace the capacitors.
To replace the caps, tin one pad. Place the cap carefully and hold it
down with something like a small flat screwdriver. Heat the tinned pad
until the caps sinks down to the pad. Remove the heat. Wait a few
moments. Remove the pressing tool. Now solder the other pad/terminal.
3) How do I get replacements, and how do I slap those
back down on
the board? Is the code on the top all I need to order more?
See, having me in your Spacecraft Design class all those years ago is
coming in useful after all. Count the caps and the markings, and email
me. I've got the replacements.
Jeff Walther