--- On Fri, 5/21/10, oz390gta <[email protected]> wrote:
> While setting up my newly acquired LC
> it was all running fine with
> sound and then I started hearing a crackly through the
> speakers and
> now there is no sound. Not even a startup sound. I have
> done a PRAM
> reset and even then there is no sound. I installed a new
> system, still
> no sound, I think it is a hardware issue, any ideas?
Either dirty contacts on the speaker or some capacitors gone bad in the audio
output circuit.
An easy test is to try external speakers or headphones. If that doesn't work
then it's likely the logic board needs some fixing.
Bad capacitors are usually easy to spot. They're small can-shaped components,
wrapped in various colors of plastic. The top end has an X or K stamped in.
That makes weak lines to rupture so the capacitor doesn't explode if hit with
too much voltage or the electrolyte goes bad.
If the top is bulged up like a dome or has some brown stuff oozing out, the
capacitor is bad. Many of the capacitors Apple used in the 1990's were poorly
made and tend to leak around their bases, getting the electrolyte onto the
circuit board.
That can cause weird problems due to small amounts of electricity going where
it shouldn't or in extreme cases it'll corrode traces and break them.
Capacitors ruptured on top will cause problems because their values change. The
worst that can happen is if the rolled up foil inside shorts out. Then it's
like the capacitor has replaced itself with a wire.
"Magic Smoke" (what really makes electronics work ;-) gets released, components
go BANG, the computer Ceases To Function and becomes difficult or impossible to
repair.
--
-----
You received this message because you are a member of the Vintage Macs group.
The list FAQ is at http://lowendmac.com/lists/vintagemacs.shtml and our
netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml
To post to this group, send email to [email protected]
To leave this group, send email to [email protected]
For more options, visit this group at
http://groups.google.com/group/vintage-macs
Support for older Macs: http://lowendmac.com/services/
