Defective generator, problem Nano V2

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gtr
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Defective generator, problem Nano V2

Post by gtr » Wed Apr 04, 2012 1:15 am

Hello world,

I have not used my Nano for 2 days. It remained in its cases and this morning I wanted to make a demonstration of my DSO Nano V2 with a friend. By connecting the generator and the probe (I did not connect the mass together like BenF says it) to visualize the square waves, here now what I have

http://www.casimages.com/img.php?i=1204 ... 702707.jpg

I reloaded it and that does not change anything. What occurs? The remainder functions correctly. If I connect the generator with high speakers, I hear the sound of the frequencies when I pass from one frequency to the other. But as you can see on the image, there is a problem.

http://www.casimages.com/img.php?i=1204 ... 702707.jpg

I hope that it is not already broken!

Thank's!

motopasscode
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Re: Defective generator, problem Nano V2

Post by motopasscode » Wed Apr 04, 2012 1:24 pm

Try changing VD to 1v/Div and TD to 500us/Div.

And try Push and Hold OK button.

gtr
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Re: Defective generator, problem Nano V2

Post by gtr » Wed Apr 04, 2012 6:25 pm

Here the result:

Thank's!

motopasscode
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Re: Defective generator, problem Nano V2

Post by motopasscode » Wed Apr 04, 2012 11:33 pm

Yah something is not right. It's not getting a good signal. If you have a multi meter test the resistance of the probes and gen leads. Maybe generator leads went bad, shorted or brocken.

Other than that I can't think of anything else. I hope others will shine in with advice.

gtr
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Re: Defective generator, problem Nano V2

Post by gtr » Thu Apr 05, 2012 10:36 pm

Hello,

R25 resistance posts on my ohmmeter “14.09K or 8.59K” and R26 posts “13.07K or 44.13K”. The value changes by reversing the probes of my ohmmeter. Obviously there is a problem with these resistances.

Thank's.

motopasscode
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Re: Defective generator, problem Nano V2

Post by motopasscode » Fri Apr 06, 2012 3:28 pm

Are you measuring resistors on the board in circuit? Most times you have to remove resistors, caps, transistors even diodes to accurately measure them because they interfere with one another while in circuit.

What I was saying in previous post is take the probes out from nano and see the resistance of probes.

gtr
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Re: Defective generator, problem Nano V2

Post by gtr » Tue Apr 10, 2012 7:58 pm

Sorry to answer also tardily.

The probes are OK, they posts 4ohm with my ohmmeter. I also compared with other probes similar, and I always obtain 4ohm. My voltmeter posts 87mV on the output of generator, it does not matter the probe used.

I as noticed as the battery discharges more quickly than front.

I cannot unsolder resistances because it is of micro component then impossible to change.

I am disappointed to note the brittleness of this oscilloscope.

Thank you.

motopasscode
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Re: Defective generator, problem Nano V2

Post by motopasscode » Wed Apr 11, 2012 12:31 pm

Hi. First grab the v2 schematic http://code.google.com/p/dsonano/downlo ... Scheme.pdf
And datasheet http://pdf1.alldatasheet.com/datasheet- ... HC125.html

What board version of V2 do you have?

You should forget about R25, R26. These are related to USB not Func Generator.

Lets make sure your 74HC125 has VCC on pin 14. Should be close to Battery voltage. Mine has 3.7v

And pin 8 about half of Battery voltage. Mine has 1.9v.

Attached pics of my Nano 2.5. I placed Ground Volt meter probe on USB shield and Red to VCC of 74HC125 pin 14 then 8.

Be careful.

gtr
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Re: Defective generator, problem Nano V2

Post by gtr » Thu Apr 12, 2012 8:14 pm

Hello,

My board version: DSO201V2.5

I placed Ground Volt meter probe on USB shield and Red to VCC of 74HC125 pin 14 then 8

Fuction Gen Out=0.8v

74HC125:
Pin 8=0.8v
Pin 14=3.7v

Thank's for help me.

motopasscode
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Re: Defective generator, problem Nano V2

Post by motopasscode » Fri Apr 13, 2012 3:41 am

Ok lets check more points.

With my battery at 3.7v I get these readings in attached pic. My DVM Ground is on USB Shield as before.

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