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Subject: 
RE: External Power Port Problem..?
Newsgroups: 
lugnet.robotics
Date: 
Thu, 2 Dec 1999 00:18:51 GMT
Original-From: 
Jim Thomas <jim.thomas@trw.!IHateSpam!com>
Viewed: 
576 times
  
Yeah, they'll replace them just this once...  You send them your 1.0 bricks
and they will replace them with 1.5 bricks.  Problem solved -- no more
battery packs for you.  Those Lego wall warts are current limited to less
than 1A (IIRC).  Your battery pack will probably deliver 10x that!  My
suggestion is that if you insist on using battery packs instead of the wall
wart then put a fuse on the line.  If you find yourself blowing the fuses
then you'll know why.

Good luck,

JT

-----Original Message-----
From: Tilman Sporkert [mailto:tilman@activesw.com]
Sent: Wednesday, December 01, 1999 4:07 PM
To: lego-robotics@crynwr.com
Subject: RE: External Power Port Problem..?


Although I didn't see an "Use only Lego approved power
supplies with the
external power connector" in the manual, I believe Lego has
no obligation to
fix your RCX brick. The connector is for an external AC power
pack, not a
custom Lithium Ion DC battery pack. That they replace it for
you is a nice
gesture. They won't have this problem with new RCX bricks
anymore, as they
don't have an external power connector. If you get one of
those, you're
screwed.

I suspect that a diode in the AC input rectifier circuit blew up. Your
Lithium Ion battery pack can probably deliver much higher
currents than the
official Lego AC power pack. That can make a difference if
you have all
motors at full power and stalled or heavily loaded. And
because your battery
pack delivers DC, all the power goes through one pair of
diodes. With AC, it
alternates between two pairs, so each diode carries only half
the power. If
the diodes aren't dimensioned for this kind of usage, they
will get warm,
then hot, and eventually fail. I recall a message with a
similar problem on
this list some time ago. If that's the case, then you will be
blowing up
your replacement bricks sooner or later, too.

Good luck!

Tilman






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