068 works ok but displays noise on screen.

[ajaxoz]

Hi I have a noise problem. Looks like the clock is bleeding into the scope circuit. Still get on the trace with switch in gnd position.
All multiplier settings have same noise level. AC, DC & GND. On test signal the noise seem to hug the square wave.
So obviously the noise is there AFTER the amp circuit.
Anybody out there got any ideas?

Cheers!
Jack

[jye1]

Please check analog power supplies with another scope if you have.

[BastienL]

Hi,

I experience the same problem. When powered by USB I got a lot of noise, i can see the test waveform but it's very noisy. And when powered by 3.7V battery, I still got noise but less than with USB. Since i don't have another oscilloscope to test the analog power supply, it's complicated to debug, did you find anything useful ajaxoz?

Thanks
Bastien

[jye1]

Can you post photos showing how the noises look like?

[BastienL]

This is when I connect the probe to the test output:

Here with a 3.7V battery

And here powered by USB

[jye1]

Thank you for the photos. Not sure where the noise came from by the photos. Please verify this way. Set the couple switch to GND. If the noise disappears the noise is from outside. If the noise is still there the noise is from inside the oscilloscope. Most common source of noises are from power supplies. The scope uses switching voltage converter to generator +5V (AV+) and AV-. These converters generate high frequency signals which must be removed. L1, L4 , C27 - C29 are filters to remove the noises. Please check these parts to see if they are all normal. Other poor connections or bad components could also be noise sources.

[jye1]

Please set time base higher to see how the noise look like. For 1KHz test signal 20ms time base is too slow.

[BastienL]

Hi, I cheked L1/L4/C27/C29 and they seems good, when the oscilloscope is on gnd i still get noise on the screen.
I don't know where i should look now.

I took better photos, here battery powered
and here with usb power
Test signal is 1000Hz.

[jye1]

This could be caused by problem in the power supply modules (BOB4 and BOB5). Please contact JYE Tech at jyetech@163.com for replacement of these boards to test out.

[BastienL]

Hi!

Yes i had forgot, but some time after finishing the building, the chip on BOB5 fall off, so i soldered it back and since i never soldered smd components, i may have damage it, that strange though cause it shows 5v at the input and -5V at the output, so it seems to work fine. BOB4 has 4.4V at the input and 5V at the output, don't know if it works right or not. I'll email you to see if I can replace them.

Thanks!