+3.3v not simple

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viewu
Posts: 13
Joined: Tue Feb 20, 2018 7:51 am

+3.3v not simple

Post by viewu »

My DSO138 has a problem I found was not simple. The +3.3v is short to ground. I first tried fix it by replacing U3. This did not fix the problem. So I removed other part in the area and test them with my meter. Parts tested good. I wanted to test U1 for the short, I had no way of doing this. Can anyone see throw this problem?
rfredel
Posts: 5
Joined: Wed Jul 11, 2018 8:50 pm
Location: 53117 Bonn; Estermannstr.124; Germany
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Re: +3.3v not simple

Post by rfredel »

Hello viewu.

I think it's the same problem as mine. Does the screen only show a white screen?
Open jumper J4 and measure at TP22. There must be the 3.3V. In the event of a short circuit, U5 and U3 become very hot. Also U1 (MCU) is still too warm
The 3.3V supply only the MCU. This has a direct short to ground on my device, so it is defective.
Unfortunately, I have no better news.

Best regards
Rainer

written with Google translator
viewu
Posts: 13
Joined: Tue Feb 20, 2018 7:51 am

Re: +3.3v not simple

Post by viewu »

Rainer I believe your diagnosis is on the QT. I open J4 and tested U1 pin9 : D3 anode: JP4 the right point; J6 pin1, all were shorted. So now what can be done? I can not see though the replacement of U1. Can you? If you can, how? Viewv
rfredel
Posts: 5
Joined: Wed Jul 11, 2018 8:50 pm
Location: 53117 Bonn; Estermannstr.124; Germany
Contact:

Re: +3.3v not simple

Post by rfredel »

Hello viewu,
changing U1 is not easy. You have to have a lot of practice in replacing SMD components.
The IC you can possibly get at st.com as a sample without payment. The name is STM32F103C9T6.
Here in Germany I can buy the IC, but it is more expensive than the whole kit.

After installation, you have to install the firmware. You can download these from the JYE website. There is also the guide how to do it.
I have not done this repair because of time constraints.

Best regards
Rainer

written with google translator
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