If you have access to a variac, you may want to gradually apply power to th=
e
circuit and observe your readings at lower thresholds before doing an
ultimate smoke test:)

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Josh Koffman
Sent: Saturday, March 01, 2014 1:02 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] IR Reflow Oven Repair

Hi all,

Update time! I am back from a trip, and I had a few minutes to take a coupl=
e
of photos of the transformer. Check them out here:

http://picpaste.com/xformer1-Bn1vWyyU.JPG
http://picpaste.com/xformer2-yZGTifoE.JPG

I am fairly convinced that this is in fact a current sense transformer. The
primary seems to be connected between the input power to the board, and the
triacs. One side of the secondary is grounded, and the other eventually goe=
s
to a pin on the Atmel processor that can be an ADC. I haven't removed it
from the circuit yet, but at the moment it measures roughly 21 Ohms on the
secondary, and 0.25 Ohms on the primary.

There is some definite damage on the board that I have no repaired yet. I
need to clean up a few traces, and I'm going to replace both triacs, optos,
and resistors just to be safe. For the few dollars, why not.

I am not sure what to do about the transformer though. In theory, it might
be fine, but that blackened portion visible in the photos makes me a little
leery of feeding it 120V.

Any suggestions on the best way to proceed? I haven't found anything yet
that matches its physical dimensions, so I am not sure what to try next.

Thanks!

Josh
--
A common mistake that people make when trying to design something completel=
y
foolproof is to underestimate the ingenuity of complete fools.
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