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Title: DSO4254B channel 2 Damaged?!? [Print this page]
Author: amy    Time: 2021-1-5 16:17
Title: DSO4254B channel 2 Damaged?!?

Customer Consultation

Hi, I bought the DSO4254B and I think there is a problem with channel 2.
When I press the AutoScale button it gives me an incorrect value (about 100V). On the other channels it works correctly.
Product purchased on November 29, 2020 from aliExpress.


[attach]4141[/attach]

Author: amy    Time: 2021-1-5 16:21
Reply

Do you swap probes to test ch1 and CH2? Does the oscilloscope still show CH2 abnormality?

Please warm up for half an hour and perform self calibration. Do not connect any test line or probe during self calibration. Then test again.

Author: Rob_ITA    Time: 2021-1-5 16:43
same probe(x1) on both channel 1(yellow) & 2(blue)...

Author: Rob_ITA    Time: 2021-1-5 16:49
see the trigger level on ch2.
I pushed 50% and DSO set to 6.2v. Why?
Label on probe comparator connector shows 1Khz 2Vp~p

Is there something inside ch2 that I can check? I've also another Hantek DSO (DSO5102P)
Author: Rob_ITA    Time: 2021-1-5 17:03
See also this...
ch2 with x1 and 5v arduino...

Author: Rob_ITA    Time: 2021-1-5 17:51
More than 30 minutes have passed since it was turned on. I disconnected all the probes from the channels and performed a series of self-calibration.
I get always different errors.

Self Calibration 1
[all 4ch]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV
2mVBW  1mVBW 500uVBW then error 52102

Self Calibration 2
[all 4ch]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV
2mVBW then error 52126

Self Calibration 3
[all 4ch]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV
2mVBW  then error 52122

Self Calibration 4
[all 4ch]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV
2mVBW  1mVBW 500uVBW
[1&2]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV
2mVBW  1mVBW 500uVBW
[3&4]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV
2mVBW  1mVBW 500uVBW then error 51201

Self Calibration 5
[all 4ch]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV then error 52131

Self Calibration 6
[all 4ch]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV
2mVBW  1mVBW 500uVBW
[1&2]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV
2mVBW  1mVBW 500uVBW
[3&4]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV
2mVBW  1mVBW 500uVBW
[1]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV
2mVBW  1mVBW 500uVBW
[2]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV
2mVBW  1mVBW 500uVBW then error 50100

Self Calibration 7
[all 4ch]
10V 5V  2V 1V 500mV 200mV 100mV 50mV 20mV 10mV 5mV then error 52132
Author: Rob_ITA    Time: 2021-1-5 18:59
After further calibrations, the procedure was completed successfully. Now I get a ground shift on channel 2.
Both channel have x10 attenuation on probe.




Author: Rob_ITA    Time: 2021-1-5 19:12
Only on ch2 ground is shifted...

Author: Rob_ITA    Time: 2021-1-5 21:30
...and in the last screen with all 4 probes connected at 1Khz, 2Vpp only the waveform on channel 2 floats up / down on the screen. The other 3 are stable ...
Author: Rob_ITA    Time: 2021-1-6 19:17
amy replied at 2021-1-5 16:21
Reply

Do you swap probes to test ch1 and CH2? Does the oscilloscope still show CH2 abnormality?

can I send you some videos to caiyijun@hantek.com in order to study the problem?
Author: amy    Time: 2021-1-7 15:02
Judging from the problem, it should be a hardware failure. Let's do some hardware tests. If you can solder, please follow these steps.

1. Open all channels, switch the volt/div between 200mV and 500mV, and check whether there is relay sound.
2. Input 1kHz/10Vpp square to four channels at the same time, their voltdiv is set to 100mV, their probe ratio is consistent. Compare and test the waveforms of several points marked in the figure below.
[attach]4148[/attach]

If you can't weld, please contact the seller for repair.

Author: Rob_ITA    Time: 2021-1-7 16:22
Can I use 1Khz/5Vpp probe compensator from my other Hantek DSO5102P or must be 10Vpp?
With "their probe ratio is consistent" you mean the same (all 4ch x1 or x10)?

ThankYou. I will test as soon as I can
Author: Rob_ITA    Time: 2021-1-8 04:40
Edited by Rob_ITA at 2021-1-8 05:29

I've used 5Vpp/1Khz of DSO5102p.
1. Yes, I've relay sound when switching between 200mV/500mV.


2. These are the results all 4ch with x1:

PointMinMax
ch11-0,085,04
ch21-0,085,04
ch31-0,085,04
ch41-0,085,04
ch12-0,085,04
ch22-0,085,04
ch32-0,085,04
ch42-0,085,04
ch133,784,38
ch232,94,38
ch333,044,4
ch432,424,4
ch1404,88
ch240,084,96
ch3404,88
ch440,084,96
ch151,843,32
ch251,843,32
ch351,843,32
ch451,843,32
ch161,72,78
ch261,72,76
ch361,72,76
ch461,72,76
ch170,461,34
ch270,461,34
ch370,461,34
ch470,461,34
ch180,521,4
ch280,521,4
ch380,51,38
ch480,51,38





Author: Rob_ITA    Time: 2021-1-8 05:41
I see on p3 differences between channels, does it mean something?

CH1 0,6 Pk-Pk
CH2 1,48 Pk-Pk
CH3 1,36 Pk-Pk
CH4 1,98 Pk-Pk
Author: amy    Time: 2021-1-8 16:39
Please set the volt/div of the four chanels to 500mV, and compare and test the waveforms of 8 points.
Author: Rob_ITA    Time: 2021-1-9 05:13
I've discovered this interesting behaviour.
I've set 500mV/div and 5Vpp/1kHz in all 4 channel. All 4 probe are x1.
If I test p7 on channel 1 and p7 on channel 2 I see a difference (violet waveform = ch yellow 1 - ch blue 2) in amplitude.
If I test p7 on channel 1 and p7 on channel 3 there's no difference (violet waveform is flat).
Also no difference in amplitude between p7 on channel 3 and p7 on channel 4.

The same behaviour when I test p8 between channels.

Could be the IC [U203] below p7 and p8?

Author: Rob_ITA    Time: 2021-1-10 18:40
When performing the calibration I notice that for each channel a line is positioned in the center, top and bottom of the screen for each volt/div in testing.

The blue line [channel 2] always reaches the others with difficulty and after a certain number of attempts it goes into error. I always get different errors depending on the vol / div it is calibrating. If I connect to the serial interface, can I get other useful information?

Author: amy    Time: 2021-1-11 12:02
Please remove these resistors in CH2 area and test their resistance value. [attach]4170[/attach]

If the resistance values are OK, then can probably judge that U203 is broken.

The model of U203 is LMH6552SD/NOPB.

Author: Rob_ITA    Time: 2021-1-11 14:49
Waiting for your answer, I inverted U203 between ch2 and ch3.  The problem remained on ch2.  I'll try to see the resistance values.  I later tried to do a reset and at the end I can only choose between French and German.  Could you tell me how to make English appear again?
Author: Rob_ITA    Time: 2021-1-11 14:51
Reset = recover system with f2 after a failure startup
Author: Rob_ITA    Time: 2021-1-12 04:48
I measured the resistance values and they are correct.

Since in point 3 of channel 2 (AD8510 U201 output) the waveform is not stable compared to the other channels I could try to invert it with channel 3. If the problem moves to channel 3 then I have found the faulty component. You say it could be a valid test?
Author: amy    Time: 2021-1-14 15:03
Rob_ITA replied at 2021-1-12 04:48
I measured the resistance values and they are correct.

Since in point 3 of channel 2 (AD8510 U201  ...

Yes. It can be tested like this.

It is suggested to exchange 8370 of the two channels to try first.
Author: Rob_ITA    Time: 2021-1-15 19:40
I did another 2 tests.

I first inverted between channel 2 and 3 AD8510 and the waveform remained unstable on channel 2. Then I inverted between channel 2 and 3 AD8370 and the unstable waveform is always on channel 2.
I can try to swap the 3 transistors (marked 3EM) between channels 2 and 3 to see if anything changes.
They all look the same and could they be MMBTH10?


Author: Rob_ITA    Time: 2021-1-15 23:38
Edited by Rob_ITA at 2021-1-16 02:03

I swapped the 3 transistors but nothing has changed (between ch2 and ch3).
I reversed the 2 mosfets (w6g) and nothing has changed (between ch2 and ch3).
Every time I do the calibration the blue line (channel 2) has difficulty in reaching the others and goes into error. What else could I reverse? The switching diode marked A7?

Author: Rob_ITA    Time: 2021-1-16 00:49
Can I verify anything in this area?

This should be the offsets for the 4 channels (pin2 of the AD8510s of each channel).
With a 5Vpp / 1Khz input signal on ch1, ch2, ch3 and ch4 and setting 500mV / div here I measure with a DC voltmeter:

Ch1: -2.37V
Ch2: -2.29V
Ch3: -2.37V
Ch4: -2.37V


Author: amy    Time: 2021-1-17 14:51
Rob_ITA replied at 2021-1-16 00:49
Can I verify anything in this area?

This should be the offsets for the 4 channels (pin2 of the AD8 ...

Please do not input any signal to the four channels, and put the four channels in the middle of the vertical direction.And then test the voltage of the four points marked in your diagram and the corresponding points of the four channels marked in my diagram.


[attach]4177[/attach]




Author: Rob_ITA    Time: 2021-1-17 19:39
No input signal (probes disconnected).

500mV/div and GND symbol in the middle of the screen for all 4 channels.

md = my Diagram
yd = your Diagram

ch1 -2,37v(md) , -2,37v(yd)
ch2 -2,29v(md) , -2,29v(yd)
ch3 -2,36v(md) , -2,36v(yd)
ch4 -2,36v(md) , -2,36v(yd)

Did you think there was some signal loss in the tracks?


Author: Rob_ITA    Time: 2021-1-17 19:54
I was thinking of something. If I remove this resistor can I isolate the AD8510 pin2 input?
If yes, I could do this for all 4 channels I could isolate the 4 points of my diagram.
If there is still voltage difference there then the anomaly could be in the area of my diagram.


Author: Rob_ITA    Time: 2021-1-18 02:43
Edited by Rob_ITA at 2021-1-18 03:01

disconnected the "cuttingResistor" for ch2 and ch3.
Same values as post #27.
I think that the problem is the area of my diagram.

On hex Inverter U33(?!?) :
I=input, O=output

p1 2,39v I
p2 1,41v O -->ch2
p3 2,35v I
p4 1,46v O -->ch1
p5 0,94v I
p6 4,97v O
p7 gnd
p8 0v O
p9 4,97v I
p10 1,46v O -->ch3
p11 2,35v I
p12 1,45v O -->ch4
p13 2,36v I
p14 4,97v (vcc)


Author: Rob_ITA    Time: 2021-1-19 00:29
Edited by Rob_ITA at 2021-1-19 00:33

I've reconnected the 2 resistor.
This is the serial output from some calibration (ended with errors).
(Remove zip extension and open with notepad.)




Author: Rob_ITA    Time: 2021-1-19 01:27
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...
Author: Rob_ITA    Time: 2021-1-19 19:15
Edited by Rob_ITA at 2021-1-19 19:27

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.



Author: Rob_ITA    Time: 2021-1-21 01:15
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?
Author: amy    Time: 2021-1-21 16:43
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?

[attach]4188[/attach]


Author: Rob_ITA    Time: 2021-1-22 01:41
Edited by Rob_ITA at 2021-1-22 01:47

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.




Author: Rob_ITA    Time: 2021-1-22 01:57
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

??
Author: Rob_ITA    Time: 2021-1-25 00:18
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).

Author: amy    Time: 2021-1-26 15:20
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.


Author: Rob_ITA    Time: 2021-1-27 18:29
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


Author: Rob_ITA    Time: 2021-1-28 05:01
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!



Author: amy    Time: 2021-1-28 16:20
That's great. You're awesome. we didn't help much.




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