Noisy signalgenerator

My calibration output is very noisy. I think i might have grounded it! It stopped working for a few days, but is now working again, just with alot of noise.

I have a regular scope, can someone point me to what i should be able to measure “place x and y” to find the faulty component?

EDIT: Forgot to say that my amplitude is very low… Is there any way to see if the U9 (74HC125) is dead?

Hi CS,

Looks very similar to the issue I had. See thread:




i still think it is caused by the ground . maybe you can check with a multimeter to see if it grounded well

the U9 Pin9 is for signal out input to U9, and then out from the U9_Pin8. you can check if the voltage on these 2 pins .if the Pin8 is normal, maybe the problem caused by the signal_generator connector or the wires between the connnector and U9_pin8,
if the U9_pin9 is normal but the U9_pin8 is abnormal, you need to check if the power of U9(Pin4 for 3.6V,pin7 for gnd) is normal, to see if the U9 is in normal state.
if the U9_Pin9 is abnormal , you may need to check the Pin_59 of the MCU is normal, maybe leaded by abnormal solder.

Thanks for your posts…
I think my 74HC125 is dead…

I have attached a picture - If i probe the blue pin, i get a fine squarewave, also at 1 MHz.
If i probe the red it gives a distorted squarewave at 1 KHz. Above 1 KHz the signal gets more distorted, and lower in amplitude!
What do you think? Should i just replace the 74HC125?

i am sorry to reply you so late , it is such a busy week for me.
i can not see your attached picture. but as your say , i suggest you re-solder the U9 , and clear this area carefully.

I would also suggest that a re-solder of ALL pins is in order before chip replacement.