Electronics > Repair

FY6900 chopped signal other issues

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Swake:
Good find. Let's hope it broke 'for no reason' and nothing else made it fail.

alonsojar:
Hi cdpar2000,
I have the same 'beauty' with the same V2.1 board level: Mine is unmodified except the front BNC connectors that I replaced by equivalent amphenol ones because center contact was failing.
By now it works as expected, so if replacing the U13 chip doesn't solve your problem and you want to investigate more, I can test in my board following your instructions (I have no idea of how this thing really works  ;D), so feel free to ask here or PM me.
Alonso

cdpar2000:
Good news!    U13 SL6KG or SGM3204 was bad.  It didn't convert +5 volts to -5 volts.  Using QuickChip I was able to remove U13.  Using very fine solder and a fine soldering iron tip I was able to replace this small component. 

I'll calibrate following some good YouTube procedures.

However, I still have one problem.  The FY6900 will not produce a signal above 5 volts.  My FY6900 60M model has a 5 volt power supply.  I assume there must be some kind of buck converter chip that increases the voltage.  I don't know what chip that is, but I hope those smarter than me can help identify that chip. 

again, thanks all for the great feedback!
Chuck P.

Swake:
Progress !!

About the output signal a manual of 2019 says this:

--- Code: ---Amplitude Vpp
Frequency≤5MHz: 1mVpp~24Vpp;
5MHz<Frequency≤10MHz: 1mVpp~20Vpp;
10MHz<Frequency≤20MHz: 1mVpp~10Vpp;
Frequency>20MHz: 1mVpp~5Vpp;

--- End code ---

I don't know for sure if this applies to your version or not, but let's assume it does.

Have you tried with a low frequency sine signal of let's say 100 Hz?
Did that signal show up on your scope as expected, no more distortion?
What is the output Vpp setting on the generator? What is the measured value on the scope? If it is not the same please experiment a bit a try to find the limits or a correlation between the 2.

alonsojar:
Hi,
Maybe chip U11 RY1303A is the one you're looking for, but is so tiny that even test it with a multimeter probe is difficult at risk to touch two pins and create a short.

https://www.rychip.com/en/pd.jsp?fromColId=130&id=510#fai_14_top&pfc=&_pp=130_509

I see they are selling in aliexpress but unsoldering and soldering can be a challenge and will require a hot air gun and some experience IMO.

Good luck!

Edit:I've found the RY1303 datasheet and it's a step down buck converter, so probably not part of your problem.
https://www.lcsc.com/datasheet/lcsc_datasheet_2410121523_RYCHIP-Semiconductor-Inc--RY1303_C370881.pdf

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