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Digital oscilloscope project/kit

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John Swift:
Hi Roy

just double checking
when you say I can only get the display to indicate DC or ground.

do you mean it does not show "AC" at the bottom of the LCD
or the trace is a straight line

if its not indicating "AC" at the bottom of the LCD then check the voltage at test point TP6  ( switch 1B terminal 6 )
+5V for DC
 +1.2V  for AC
and 0V for GND

if its the trace not responding
check C1 is 0.1uF (marked 104)
if for instance a very small value capacitor that should be C2 , C3 , C5 or C7
virtually non of the AC voltage at the input connector will be passed onto  switch 1A terminal 3

   John

wheeltapper:
Hi John, thanks for the reply.

It is the indicator on the LCD, it doesn't change to AC.

I was going to do some voltage checks as soon as real life gets out of the way. :bang:
I'll get back with the results.

Cheers
Roy.

wheeltapper:
Thar's interesting, I'm getting 3.8v on AC.

I will look further.

Roy.

Will_D:

--- Quote from: RobWilson on January 06, 2016, 05:49:24 PM ---DSO  Manual attached for the pros to cast an eye over .
Hope that helps ,Rob

--- End quote ---
Cheers Rob for posting the manual.

 I must say that is one of the best manuals I've seen in a while for such a cheap kit!.

John Rudd:
3.8v is too high....should be around 1.4v.....it looks like the software isnt switching as a result...

I suspect the resistors are the wrong way round....

You need to check the values of the resistors in the chain......

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