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Seumeneur

Analog Discovery WaveForm Generator Failure

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Hi,

First, The Analog Discovery 2 is a very handy device and i am very pleased with all the functionality it offers.

I got a problem with my device. The channel one of the wave form generator is not working any more. Here is the full the story. i mixed up the scopes for the signal generator and the oscilloscope and i ended up trying to measure a voltage of about 80v with the scope connected to waveform generator. As a result the device disconnected from my laptop. I noticed my mistake, unplugged the scope and tried to reconnect the device. It does show up in the list of available devices with all values of the register, S/N, state... But once i have clicked on 'select', an error pops with 'communication with the device failed'. I connected an external power supply to Analog D and this device can now be connected to Waveform (?!). If I try to set a sinusoidal signal on the channel one of the waveform generator, it shows either a clipped signal or absolutely nothing depending on the Vpp voltage. Also, their is a spurious 3V drop between ground and the output of the channel 1 To finish, the device warms up very quickely.


Does anyone has an idea how to fix that ? To be honnest, i have made an huge mix-take with the device, do you think that someone at Digilent will agree to have look at the device ?

Edit: Waveform indicates a consumption of 800mA / 4.8V on the AUX power supply, the temp is around 50 °C. Also there is a sound emitted by the device when connected, like a whistling.
Best Regards,

Nicolas

Edited by Seumeneur

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Hi Nicolas,

I’m sorry to hear that. Unfortunately, we also don’t have the resources (tools and technicians) to repair the broken boards.

Even if you didn’t make the mistake to connect the wave-gen with the scope and everything was wired up correctly, you would’ve ended burning your device because Analog Discovery 2 is not capable of measuring 80V, its limit being 50V. Since this isn't a manufacturing defect, it is also not covered by warranty so we can't replace it.

I’m sorry we can’t help more.

Best regards,

Bianca

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Yeah, I know it is on me.


But I usually do not give up easily. Here is my trouble shooting.

I have managed to spot a short circuit on the output stage of the AWG1 caused by a fried op amp, i changed it and the consumption is now back to a std level (300mA), the board can now be connected to my laptop without power supply.


The AWG1 generates a wave, but there are two problems.

There is, as already mentioned, an offset and i can not correct it by calibration of the high gain AWG1. Also, the spectral behaviour changed : there is a loss in the generation of the wave, if i select one volt for the peak to peak voltage, the amplitude of the effectively generated wave decreased as the frequency increased, there is a low pass filter somewhere.

I insist : this offset appears only on the High Gain Calibration procedures and also on the scope.

The I/V stage : The Audio works fine! No problem! No loss at high gain frequency. So the generation of the wave is ok nothing bad append to the DAC. The AD8068 is a dual op amp, the figure 19 of the documentation is missing, is the Right Audio circuit and the out circuit of the AWG1 use separate op amp ?

Could you provide me the Figure 19 . This would be priceless for me.

Also :  The offset is provided by a chip AD5645R which also provides voltage for the on board power supply, the latter work well.

Best Regards,

Nicolas

 

 

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Verify the AWG1V2_REF, which should be 1.2V, and the AWG1/2_REF should be 1V
These are located on the bottom of the board.

IC13 is above the right side of connector soldering:

i3.thumb.png.cc5f5fb1c859e0e76f72c9f2390b0e04.png

 

IC42 above IC13:

i4.png.30475f75c89e60508a160ca50e9c42f8.png

 

Verify the +/- 3.3/5.5V

IC15 is on the right side of TxDAC

i2.thumb.png.08412f36feb40e739cb04aae63236216.png

 

IC16 is on the lower edge, under the header, almost in the middle:

i1.thumb.png.a4a4b345085eacb78efcb772f3d62b51.png

 

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Hi @attila,

Thanks for the figure and the typons ! Your are right there is a problem with caching. I will test the voltage you mentioned during the next days. I have checked the output of the Audio on my scope, everything is ok. I think that the Feedback capacitor C163 may have been damaged causing the cut off frequency of the RC cell to have moved. I will check.

 

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Hi attila.

i am trying to troubleshoot on some "broken" AD2's. browsing through all sorts off semi related forums etc. i found this thread. i work at university of Aarhus, Denmark in the department of  electronics engineering and the AD2's are used a lot in our education. but now and then student are "torturing" the devices and my job is to either repair them or to asses if it is a warranty case. 

often the i try to do the calibration wizard to get a hint of what's wrong. and i often i get the same error. when i get to typing in the measured values for wavegen 1 i get stuck with the -5 V measurment because it shows - 0.714 ish volts and the wizard are not able to proceed. that is why i found you test interesting and thought i simple check of reference voltages might reveal something. but when i measure the points in your description i do get all the right voltages except the "AWG1/2_REF should be 1V" (as i understand as two seperate points that should read the same voltage. AWG1_REF and AWG2_REF.) these both read 1.2 volts. Am i understanding this right. that this should be two seperate points? if yes does it tell you something that AWG1/2_REF is 1.2 volts and not 1 volt? 

regards Søren

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Hi @sbrun

The 1.2V for VREF_AWG1/2 (VREF1V2_AWG) is correct. The REFIO (VREF1V_AWG) for the DAC should be 1V.
https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual#awg_reference_and_offset

Probably the output amp is damaged. Here you can see this IC16:
https://reference.digilentinc.com/analog_discovery_2/refmanual#figure_19

image.thumb.png.e91ba93fb52a302711f21c4c7825bde0.png

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