On Mon, 14 Jun 2010 04:23:13 -0700 (PDT), powerampfreak
wrote:
But the curiousity took control over me. I cleaned up after the blown
fuse. Put a new one (1.6AT) - connected it to mains - and it works!
All channels and functions seems to operate just fine.
Congrats. I would have used an isolation xformer and variac, but if
you have a supply of fuses, that works.
There are really no sign of flames anywhere. One thing which I haven't
paid any attention yet, is the mains filter which is an integrated
block of some coil and filtercaps encapsulated.
Probably made by Corcom.
http://www.corcom.com
They can be blown by a lightning hit, but not much else.
I will change the Y and X caps to make sure they're ok.
Are there any MOV disks around the AC power jack? If yes, look for a
tiny hole where the flames exited.
I've never seen a shorted secondary side make the mains fuse explode.
Just primary shorts has the power to do this, in my opinion based on
hundreds of smps repairs.
Now that you mention it, you're right. Secondary shorts usually just
cause the switcher to shut down. If there are big fat capacitors on
the output lines (not commonly found on PC switchers), they could
store enough energy to blow the primary. I've seen secondary shorts
blow the primary fuse in "brick" type switching power supplies, but
not resulting in the blackened smoking mess you described. That would
require a short on the primary side.
Anyway, it appears that I've got another nice looking four channel
oscilloscope on my bench! :-)
However, this begs the question of what caused the flames and smoke?
If the fuse was intact, it's unlikely. If it was an AC power line
fault of some sort (lightning hit, lost neutral, hi-v distribution
line falls on power line drop), it would have destroyed other pieces
of test equipment in the lab. Pardon my suspicious nature, but
methinks you should run it with the covers off and keep an eye on this
scope for a while.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558