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Digital oscilloscope project/kit

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John Swift:
Hi Roy

the voltages measured will depend in the input current into pin 13 of the micro controller
but this picture shows  what I expect

   John

wheeltapper:
Typical! I get that fixed and now the trace is stuck at the bottom of the screen. :doh: :doh:
It won't any how I try.

Roy.

EDIT
test point V1 is now -1.4V instead of 0.test point V2 has also gone negative.

John Swift:
Hi Roy

what did you re work to fix the original problem ?

with switch 1 grounding the input
pins 1 , 2,  3 , 4 on switch 2 (SEN1) should all be at 0V
 the switch common (pin2) is connected to the input pin 5 of the unity gain buffer U2B
the voltage at TP 2 should be the same

possibly a splash of solder is shorting some thing to the negative supply AV-

  John

PS

how negative is TP2
just noticed U2 negative supply pin 11 is next to pin 10 U2C's input
 which is connected to switch SEN2 's common

wheeltapper:
Yippee.
I think I've fixed it.
the first thing I did was reflow R18, that fixed the AC problem.

I just reflowed pins 1 to 7 on IC U2 and all the voltages are correct now.

PHEW!

thanks for the help.

Roy.

John Rudd:

--- Quote from: wheeltapper on January 07, 2016, 10:49:12 AM ---Yippee.
I think I've fixed it.
the first thing I did was reflow R18, that fixed the AC problem.

I just reflowed pins 1 to 7 on IC U2 and all the voltages are correct now.

PHEW!

thanks for the help.

Roy.

--- End quote ---

Excellent! Glad you fixed it... :zap:

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