DIY audio scope - cheap

[flat5]

I have more tweezers now. Still have not found the previous order of 6 from Banggood.
I like the one you have with the sliding thing. You could use less solder on the resistors but it does not matter.
How did you take that photo? Do you have four arms and hands? Oh...I guess you might have used a tripod.

 

[debe]

Finaly worked it out. Has any one else found theres a lot of noise on the waveforms? Is it the op amp creating the noise?

 

[Nigel Goodwin]

Finaly worked it out. Has any one else found theres a lot of noise on the waveforms? Is it the op amp creating the noise?

I commented on it when I build mine, not had time to look in to it yet though (or upgrade the software)

 

[debe]

This is the switch CPL in GND position, so the noise definitely is internal. Might have to investigate it.

 

[Nigel Goodwin]

This is the switch CPL in GND position, so the noise definitely is internal. Might have to investigate it.

I was planning sticking my Rigol scope on the output of the opamp to see what noise was coming out of there.

I seem to recall I had the shift problem as well, and it was cured by following the setting up procedure?.

 

[flat5]

The setting up procedure did not help me after removing power. The problem returned on next power up.

 

[debe]

My base line stays in the center of the screen & stays there when re powered. Guess il just have to get the Kenwood CRO out & see where this noise is comeing from when I get some spare time.

 

[flat5]

You have a later version of the firmware. I don't get the data you show on screen such as frequency.
I suspect there are some bug fixes too. One is documented.

 

[flat5]

MCU88, re post #46
Yes, the shipping had one great feature. Every article had it's own zip lock bag with computer printed descriptive labels! Not someone scribbling as fast as they can with a dried out pen on a heat sealed packet.

otoh, they packed a bag of 20 IR leds with an aluminum project box without enclosing the box with packing foam.
Two or three leds were crushed. I know two are destroyed. Arrived in three weeks.

 

[debe]

On screen Data is obtained by holding down the OK button longer than 2 seconds to display it or remove it. They should be about the same units as I purchased mine about the same time as yours flat5.

 

[flat5]

You are correct, debe.
Remember the animated TV show, Dr. Katz, Professional Therapist?
Somehow this scope reminds me of it

 

[Nigel Goodwin]

On screen Data is obtained by holding down the OK button longer than 2 seconds to display it or remove it. They should be about the same units as I purchased mine about the same time as yours flat5.

I'll have to try that

 

[debe]

Did a little investigating today. CRO settings were probe 1:1, Time 10uS,Vert 1mV. The sawtooth was taken at TP25 V-. The other one is the probe just held near & betwean Q1 & Q2, to me there seems quite a lot of radiated energy from the switching side of the negative 5V supply

 

[flat5]

Could you kill that circuit and inject -5v?

 

[debe]

Think il just wait at this stage, till the one ive ordered from a seller in Hong Kong that is supposed to be fully assembled. And see how that one works.

 

[debe]

Well got it today but, its not fully assembled. It does have all the surface mounted components fitted. Im quite happy to pay the $8 more for this kit. At least for us older folk that have trouble with surface mount components that's ok. Now need to find the time to assemble the rest of it.

 

[flat5]

Please let me know if you ever find a good case for it.
Not to tell you what to do, but it might be informative if you do not complete the -5v part so you can test to see if that is the noise source.

 

[Tony Stewart]

But with only 200kHz BW, when you get RF problems or ns or μs glitches, it wont help.

All digital is Analog and most Analog gets interference from or generates RF.
So all logic depends on RF principles and problem avoidance to work.

How's that for logic?

 

[flat5]

So we're screwed?
debe thinks the -5v supple may be producing lots of noise. This is possible.
If it can be replaced by a bench supply for a test it may prove fruitful.
Gotta know which circuit to blame. Hopefully one circuit.

 

[Tony Stewart]

They cheated you with std quality caps instead of low ESR polymers for C24,25
https://www.digikey.com/product-search/en?pv13=128&pv63=489&FV=fff40002,fff80532&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

That should improve things a decade or two