White screen, lm1117 is heating

[jye1]

We'll be happy to send you replacement chip. Please contact us at jyetech@163.com.

Can you check the voltage at the input pin of LM1117? Just to make sure it is the chip's problem.

[rickseiden]

With the three pins pointing down, and the one big pin facing up, numbering the pins from 1 to 3 from left to right, I get 3v across 1 & 2 and 8v across 1 & 3. I get about 9v out of the power jack.

Code: Select all

  ____
 |    |
+-------+
|LM1117 |
+-------+
 |  |  |
 1  2  3

[jye1]

These results are good. But you said you got 2.25V at +3.3V test point. The test point was actually the same node as pin 2 of LM1117. Either one is incorrect. Can you double check?

[rickseiden]

I guess I should have let it heat up before taking the readings. I'm getting 2.4v between 1 and 2 and 3.5v between 1 and 3 after it heats up.

Also, I noticed that the two 3.3v spots on J3 and J5 are .1v lower than pin 2 when measured from pin 1. So pin 1 to 3v3 on J3 is .1v lower than pin 1 to pin 2. But the test point near the LM1117 is directly connected and equal to pin 2.

Rick

[rickseiden]

Should R30 be unpopulated? I was just looking at my board, and R30, right near the 1117, is unpopulated.

Rick

[r0ck]

Should R30 be unpopulated? I was just looking at my board, and R30, right near the 1117, is unpopulated.

Rick

Yes. Its Step 1.7 on the first page of the User Manual.

[rickseiden]

I had forgotten that step 1.7 had us remove that resistor. So it is normal for there to be nothing there.
Rick

[rickseiden]

bump

I guess I should have let it heat up before taking the readings. I'm getting 2.4v between 1 and 2 and 3.5v between 1 and 3 after it heats up.

Also, I noticed that the two 3.3v spots on J3 and J5 are .1v lower than pin 2 when measured from pin 1. So pin 1 to 3v3 on J3 is .1v lower than pin 1 to pin 2. But the test point near the LM1117 is directly connected and equal to pin 2.

Rick

[rickseiden]

Since I wasn't getting anywhere with support, I went ahead and bought my own AMS1117 3v3 chip and replaced it on my DSO. The new chip is doing exactly the same thing. Heating to the point where you can't touch it. The screen stays white the whole time.

Can someone at JYE Tech please help with this? I have a useless brick right now.

[jye1]

Hi Rick, did U1 get hot too? If U1 was hot it might have been damaged. Please contact us at jyetech@163.com for a board replacement.