Just blew two 3.3v regulators SOLVED

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5wUBA5wa
 
Posts: 12
Joined: Sun Jun 29, 2008 5:44 pm

Just blew two 3.3v regulators SOLVED

Post by 5wUBA5wa »

EDIT: Misplaced a couple resistors. Problem solved. Now to burn the fuses..

Was working on the main board at home and didn't have a PS to test the voltages of each rail as done by ladyada in the make section so I went ahead and finished the entire power supply. So I went to school, hooked my TinyISP AVR controller to my computer, and then to the board to see if I could program the microcontroller. Immediately IC1 (the 3.3v regulator) started smoking, and turned brown. Darn.

I looked closely over everything I had done, resoldered a few parts, cleared off some resin. I then reattached the second regulator I happened to have, and decided to test the voltages like I should have back in the PS section. So I steal one from upstairs at the school, and attach the leads (4.0v), and the 3.3v regular burns up again. WTF??

First question: All the parts, sans the LED because I am not sure of the polarity, are connected and the soldering is good (I've checked it many times). What could cause this? What am I doing wrong?

Second question: While I figure out the answer for the first question, while waiting for a replacement for IC1, should I go ahead and start finishing up the other parts?

Bleh.

Thanks yall
Last edited by 5wUBA5wa on Thu Mar 25, 2010 8:24 pm, edited 1 time in total.
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c.b.
 
Posts: 15
Joined: Thu Oct 15, 2009 3:39 pm

Re: Just blew two 3.3v regulators

Post by c.b. »

was by any chance jumper JP3 at your tiny usb closed? This jumper puts 5V on your Wavebubble's 3V3 rail. When programming 3V3 targets, the jumper has to be open and the target device has to provide its own supply.
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5wUBA5wa
 
Posts: 12
Joined: Sun Jun 29, 2008 5:44 pm

Re: Just blew two 3.3v regulators

Post by 5wUBA5wa »

Thanks for the reply.

Yes, it was closed, but again I tried powering with ~4v on its own with an external DC power supply and the same thing happened.

I'll try to get ahold of a camera and up some pics of my PCB, might take a day or two. Does anybody have an answer to my second question?
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