Electronics > Repair

34461A white screen cannot start

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Hello everyone, I have a 34461A that needs to be repaired. At first, its fault was a white screen, but later it turned into a black screen. After reading the forum and maintenance manual, I found that the FPGA power supply voltage was very low, and the DS200 on the motherboard kept flashing. I suspect it may be due to the power overcurrent protection caused by a short circuit in SPEAR320S-2.

We replaced the SPEAR320S-2 with a brand new one, but it turned on with a white screen and the FPGA indicator lights turned on normally. The DS200 only turned on the left half of the yellow LED.

Now, I have found that there is a CR327 capacitor behind the MCU motherboard that is short circuited. I think it is not a capacitor short circuited. I want to know where one end of the capacitor is connected to GND and the other end is connected to? If you can help me, thank you very much!

It would be nice to see how this one ends ups.  :popcorn:

Take your meter in ohms mode and go over each and every single one of caps. Whatever looks __ off __ blow off with air and check again with LCR meter.

once again 

sad to see this problem  ...   

Does the mcu have busted  because it was getting too hot ?

Voltage lines problems,  spikes  etc ...

or the bga's / solder balls are not fully soldered ??  but you said  there is some shorted caps ????

I applied 1.4V/1A to both ends of the short-circuit capacitor, and the results obtained from thermal imaging showed that the line from tps65070 to the short-circuit capacitor was heating up, about 30 degrees Celsius. As the voltage and current I applied were not significant, I was worried about burning the line. Upon inspection, it was found that 44/45/46 (AD_IN2/3/4) of tps65070 was connected to GND, which should be the foot position of the touch screen. However, all three outputs of tps65070 are very normal, with 1.2V/1.8V/3.3V being normal.

Thank you very much. I think I will try blowing off tps65070 when I am at a loss. I am worried that too many things will be dismantled, leading to the expansion of the malfunction. I am still a novice in the hot air gun.

you have low temp  chipquick solder paste in a syringe

just need to order a stencil .... or not ??


yeah expensive ...


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