Title: [SOLVED!!] DSO4072C Both channels BAD. [Print this page] Author: X-Blade Time: 2018-7-11 19:10 Title: [SOLVED!!] DSO4072C Both channels BAD. Edited by X-Blade at 2018-8-26 06:24
Hello.
I bought an hantek DSO4072C from a seller from ebay.
It was working good but after few days both channels went bad.
Seller dont answer my messages and left me alone with the scope.
When I press Autoset button both channels turn on with a lot of noise, specially the CH2.
I can solder and replace components, just tell me what to replace and part numbers, if you can.
Can anybody help me, please?
Thank you.
Author: Newbee Time: 2018-7-13 08:08
Hello you can try this :Remove the probe Press Utility button----Self Calibration---Confirm then wait for a monent, Restart the machine. Good luck for you.
Sorry for my bad English Author: X-Blade Time: 2018-7-14 05:35
Thank you for your help Newbee.
Unfortunately I tried it but if hangs on 13/38 forever.
I will try to send it to somebody who represents Hantek.
This cheap chineese oscilloscopes are more a toy than a tool.
My hitachi V212 analog one resists to ervery abuse I subject it. Author: amy Time: 2018-7-19 09:07
X-Blade replied at 2018-7-14 05:35
Thank you for your help Newbee.
Unfortunately I tried it but if hangs on 13/38 forever.
I will try t ...
Sir, in your picture, did you input any signal to the channel? Author: X-Blade Time: 2018-7-20 05:16
Hello amy.
Yes is connected to the internal 1khz output on the panel.
It acts like there is no ground connected.
Very strange.
It started to do this after i was measuring an inductor SRF without caution or some problem related to the common ground. Author: X-Blade Time: 2018-8-1 02:45 Edited by X-Blade at 2018-8-1 03:12
Hello friends.
Thank you for all your support.
I was searching another forum and I found the schematic (not official / Reverse-engineered) of the both Channel inputs:
In another thread I saw someone reporting a similar problem , so I replaced all the 5 sot-23 components of each channel:
BAV99 (marked A7), MMBTH10 (marked 3EM), MMBF4393 (Marked 6G) and the 2 x BC846B (marked 1B)
Now both channels are working but still not working correctly but exactly in the same way:
I connected the probe to the front calibration output (5v @ 1KHZ), probe at 1X and channel with 1x setting:
Looks good and accurate, but when I try to change the vertical position the amplitude of the waveform decreases and signal get distorted:
Interesting thing: I AM NOT ABLE TO BRING THE WAVEFORM BELOW THE CENTER HORIZONTAL LINE FROM THE GRID BUT ABOVE IT MOVES CORRECTLY, expept the variation on the amplitude.
Both channels behave the same.
I have another oscilloscope (analog) I can perform some measurements.
Any suggestion?
I found that -5V rail from 79M05 is putting out -7,4V (-5V Testpoint) . It looks like the regulator is gone, I will try to get a new one, replace and retest.
Cheers. Author: X-Blade Time: 2018-8-26 06:23
FINALLY it was solved.
