DSO4254B channel 2 Damaged?!?

Rob_ITA

Rob_ITA replied at 2021-1-11 14:49
Waiting for your answer, I inverted U203 between ch2 and ch3.  The problem remained on ch2.  I'll tr ...

Language problem solved editing /config/root/system.inf and restarting.
Changed the value of Lans in 163190. Now I can select between ENG, ITA, etc...

Rob_ITA

When I touch L1302 waveform on ch2 goes up.

Where does the other side of the inductor go?
It ends in a VIA but I don't know where it comes out.

Rob_ITA

Rob_ITA replied at 2021-1-18 02:43
disconnected the "cuttingResistor" for ch2 and ch3.
Same values as post #27.
I think that the probl ...

Maybe I need to lower voltage on p1 to slide down waveform on ch2, but how?
Do you agree?

amy

Please heat the scope for 30 minutes, then short circuit the signal terminal of CH2 to the ground (connect the core of BNC to the metal ring, like the picture), and then perform the calibration. Is it possible to pass the calibration?

Rob_ITA

I did as you asked. Left on for 1 hour but it goes into error.
I read do_cal_bias:Try zero ch1 for 7 times.
I think  that at software level the channels are numbered starting from 0 and ch1 is my physical channel 2.
From the serial interface I understand that it is unable to calibrate the gnd on channel 2.

Rob_ITA

And can you explain what does it mean these rows?

get_avg_pkpk_value:-223318,-58, 2, -57, -59
get_avg_pkpk_value:-27043,-7, 2, -6, -8
get_avg_pkpk_value:-219489,-57, 2, -56, -58
get_avg_pkpk_value:-207685,-53, 2, -53, -55
get_avg_pkpk_value:411965,107, 2, 108, 106
get_avg_pkpk_value:488950,127, 0, 127, 127

Maybe

get_avg_pkpk_value: sampleValue,num1, num2, num3, num4

num1 = quantized value on channel 1
num2 = quantized value on channel 2
num3 = quantized value on channel 3
num4 = quantized value on channel 4

??

Rob_ITA

Rob_ITA replied at 2021-1-19 19:15
When I touch L1302 waveform on ch2 goes up.

Where does the other side of the inductor go?

when I apply a voltage to the resistor [01c = 10k] indicated by the blue arrow the square waveform on channel 2 goes down.
Maybe the problem is here.
This is the output of Hex Inverter. Input is coming from fpga U55(maybe).

amy

Please setting the four channels to 500mV/div, and use a scope to view the voltage curve of these four points CH1/CH2/CH3/CH4 on above picture. Is the voltage at CH2 changing?

In addition, without inputting any signal, check whether the line can be seen in all volt/div of CH2, or whether the line can be seen when move CH2 up and down.

Rob_ITA

In doing what you asked me, I noticed an important anomaly.
By measuring the resistance value indicated by the yellow arrow I noticed that:
ch1: 170K
ch2: 180K
ch3: 170K
ch4: 170K
I try to measure it after removing it to verify that it is not damaged. The code shows 88D = 806K

Rob_ITA

I finally found the solution !!
I reversed this feedback resistor between channel 2 and 3.
Channel 2 now has a stable signal with no oscillations. The resistors, after unsoldering them, were the same (~ 806k).
I think the problem was due to a dirty weld.

Performed a correct calibration without errors (now the signal on channel 2 during the calibration was easily aligned with the other 3 channels).

Thanks for the advice and support!