FG085 - Static Waveform Output

FG085 - Static Waveform Output

Postby pheff » Tue Feb 02, 2016 3:18 pm

I just finished building my FG085 and carefully followed the instructions and double checked solder connections and polarity.

Initially upon powering up with included power supply I got only a blinking LCD backlight - no text or functionality from the device. After reading some of the threads I tried a different power source and got the FG085 to boot up and appear to have functionality - all the buttons work and the display works.

However, it is only outputting a static 80Khz sawtooth/triangle wave. None of the settings affect the output - waveform, frequency, Amplitude, offset - all give the same output.

Any suggestions or is the unit dead?

Thanks,

Paul
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Re: FG085 - Static Waveform Output

Postby jye1 » Wed Feb 03, 2016 1:30 am

At which point did you check the output? Did you try probe directly at the output connector on the back of PCB? And what was the amplitude of the 80KHz singal?
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Re: FG085 - Static Waveform Output

Postby pheff » Wed Feb 03, 2016 8:48 pm

I tested the FG085 via the BNC connector on the front panel. I used a BNC-BNC cable directly connected between the FG and the scope.
I don't recall the amplitude but was using .1 V/ div - if that helps at all. I don't always have immediate access to an Oscilloscope.
Thanks,
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Re: FG085 - Static Waveform Output

Postby jye1 » Thu Feb 04, 2016 2:50 am

If possible please probe at back on the PCB. Just to rule out it was not a cable connection problem.
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Re: FG085 - Static Waveform Output

Postby pheff » Thu Feb 04, 2016 2:58 pm

Thanks I will check that in the next couple of days and respond.

Paul
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Re: FG085 - Static Waveform Output

Postby pheff » Tue Feb 09, 2016 3:05 pm

OK, I was working with my professor and a scope yesterday checking various circuits against the schematic. We took the output signal directly off the board with no change.

Tracing back the circuits the problem appears to be with either U3 or U13. The FG was set to a 10Khz Sine Wave and the input to U3 was a perfect 10khz Sine wave. However the output of U3 and U13 is showing a cross of 40mhz sawtooth/sine wave. The power supply is providing a steady +/- 12 volts.

Any suggestions?
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Re: FG085 - Static Waveform Output

Postby jye1 » Wed Feb 10, 2016 3:16 am

Can you do a careful visual inspection about the soldering? Just to check for bad solder joints. If you find something please re-touch it with an iron and see if the problem gets fixed. Otherwise, please contact JYE Tech at jyetech@163.com for a replacement. We do not suggest to do further troubleshooting since most components are SMD and it could take a lot of time.
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Re: FG085 - Static Waveform Output

Postby pheff » Mon Feb 22, 2016 4:25 pm

I did a visual inspection under magnification of the board and did not find any issues.
I did complete the DSO-038 Oscilliscope kit and again tested the output of the FG with a square wave - I have attached an image of the results.

DSC_0501 (2).JPG
DSO038 Reading of FG


I think I need a replacement - please let me know how we swap out the function generator.

Thanks,

Paul
Attachments
DSC_0502.JPG
Operating FG
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