DSO4254B channel 2 Damaged?!?

amy

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.


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

Rob_ITA

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

Rob_ITA

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:

	Point	Min	Max
ch1	1	-0,08	5,04
ch2	1	-0,08	5,04
ch3	1	-0,08	5,04
ch4	1	-0,08	5,04
ch1	2	-0,08	5,04
ch2	2	-0,08	5,04
ch3	2	-0,08	5,04
ch4	2	-0,08	5,04
ch1	3	3,78	4,38
ch2	3	2,9	4,38
ch3	3	3,04	4,4
ch4	3	2,42	4,4
ch1	4	0	4,88
ch2	4	0,08	4,96
ch3	4	0	4,88
ch4	4	0,08	4,96
ch1	5	1,84	3,32
ch2	5	1,84	3,32
ch3	5	1,84	3,32
ch4	5	1,84	3,32
ch1	6	1,7	2,78
ch2	6	1,7	2,76
ch3	6	1,7	2,76
ch4	6	1,7	2,76
ch1	7	0,46	1,34
ch2	7	0,46	1,34
ch3	7	0,46	1,34
ch4	7	0,46	1,34
ch1	8	0,52	1,4
ch2	8	0,52	1,4
ch3	8	0,5	1,38
ch4	8	0,5	1,38

Rob_ITA

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

amy

Please set the volt/div of the four chanels to 500mV, and compare and test the waveforms of 8 points.

Rob_ITA

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?

Rob_ITA

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?

amy

Please remove these resistors in CH2 area and test their resistance value.

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

The model of U203 is LMH6552SD/NOPB.

Rob_ITA

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?

Rob_ITA

Reset = recover system with f2 after a failure startup