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DSO 2250 usb Hardware problem

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Post time 2019-4-4 15:34:04 | Show all posts |Read mode
Repairing an impulse power supply unit, I connected the probe ground to the ground on the hot side of the converter (to  minus of  the rectifier capacitor). After that, a message appeared on the computer screen that the usb port is overloaded. On the board, I found that the D400 diode was shorting the + 5 volts to ground. I removed the diode, checked the voltages at C137 = 3.3V, C140 = 1.2V, C430 = 5V, C401 = 5V. Now there is no overload messagebut  the indicator LED does not glow and the computer does not find an oscilloscope. I ask for help in repairing the oscilloscope.

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 Author| Post time 2019-4-4 18:52:55 | Show all posts
Edited by electronic at 2019-4-4 19:01



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 Author| Post time 2019-4-4 19:04:21 | Show all posts

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 Author| Post time 2019-4-4 19:07:48 | Show all posts

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 Author| Post time 2019-4-5 14:27:52 | Show all posts
Edited by electronic at 2019-4-5 15:54

Dear Support. Can anyone suggest a solution. I need your help.

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 Author| Post time 2019-4-5 15:53:40 | Show all posts



Between pin 20 (VCC) and pin 21 (GND) of the CY7C68013-100AXC microprocessor is 3.3 V.
Between pin 17 (D PLUS USB) and pin GND the   resistance is 75 ohm
Between pin 18 (D MINUS USB) and pin GND the resistance is 73 ohm
Is this normal?

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 Author| Post time Yesterday 16:24 | Show all posts
electronic replied at 2019-4-5 15:53
Between pin 20 (VCC) and pin 21 (GND) of the CY7C68013-100AXC microprocessor is 3.3 V.
Between pi ...

I changed the CY7C68013A-100AXC chip and my oscilloscope started working. But while it is impossible to call  that its  work is  correct. I fed a 50 Hertz 15 volt sine wave to both channels and I see that the sinusoid on the first channel has a dip at the top. Her form is distorted. This is the first. The second problem is that I can not push the sinusoid image apart across the width of the screen, changing the value of Time / div.
When I try to start the calibration with the AVTO button, my horizontal calibration can not complete. Can someone from the support tell me where I should look for faults
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