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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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