U4 blew

General discussion and support for the Peaberry SDR V1.

U4 blew

Postby dcochran » Sun Mar 24, 2013 1:22 am

I had the peaberry working on a windows 7 machine as a soundcard. I killed power to the peaberry and unplugged the usb cable. I plugged the usb cable into the machine that is going to me its home and powered on the peaberry. I smelt smoke and my computer turned off. I unplugged the peaberry and restarted the computer. the computer came back up and I started checking out the peaberry. U4 looked damaged between the two pins furthest from the USB port I checked voltage to pin4 of U4 and it reads 3.265 volts. None of the other pins show voltage.

When I replace U4 (because it looks cratured between those pins) what other tests should I perform? Everything worked fine from a different machine. any advice? Thanks in advance.
dcochran
 
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Re: U4 blew

Postby AE9RB » Sun Mar 24, 2013 3:05 pm

The only function of U4 is to protect from ESD or transient voltages from entering through the USB jack. The radio will fully function without it.

As a guess, U4 may have been installed rotated 90 or 180 degrees incorrectly. This could have shorted the USB voltage supply. The USB spec has a provision for this situation. Your computer should have shut down power to its USB port when it detected more than 5mA of current. You might want to look into why that happened.

Before you power up the Peaberry again, I'd check your work around R12/R13. Normally, the Peaberry will draw <1mA from the USB power but obviously something cause a short. If it wasn't U4, you'll definitely want to know what it was before you try again.
73 David AE9RB
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Re: U4 blew

Postby dcochran » Mon Mar 25, 2013 11:25 pm

12.50V R1 9.68V
13.27 D1 12.50
12.50V C1
12.50V C2
4.96V C3
3.302V C4
4.96V U1
3.302V U2
4.95V R14
2.205V R15
2.205V R16 .656V
.656V C21 -.001V
.658V and .000V Q3 2.212V
U3 .014V, .034V, 4.96V, -0V, 4.96V, 4.96V
U4 3.264V, -0V, -0V, -0V
.023V R2 .018V
.024V R3 .019V
R12 -.000V
R13 -.000V
R4 -.000V
R5 3.262V
U11 Top Row 0,0,0,0,4.96V
U11 Bot Row 4.63,.030V, 0,0,.030V
U9 Left Side 3.289V,3.289V, 0V
U9 Right Side 3.299V -.001V, 1.627V
U9 Top 3.297V, Bottom 3.297V
3.297V R48 3.3V
3.297V R49 3.3V
2.482V R17 2.477V
2.482V R18 2.477V
2.482V R19 2.476V
2.482V R20 2.475V
2.482V R21 2.487V
2.481V R22 2.485V
2.482V R23 2.487V
2.482V R24 2.489V
2.487V C25 2.481V
2.481V C26 2.486V
2.482V C27 2.488V
2.482V C28 2.489V
2.48V C23 0V
2.487V C29 2.478V
2.485V C30 2.525V
2.485V C31 2.4V
2.488V C32 1.821V
2.390V R25 2.350V
2.549V R26 2.238V
2.96V R27 2.49V
1.809V R28 1.77V
0V C33 2.292V
0V C34 2.211V
0V C35 2.241V
0V C36 1.791V
U6 pad 2 to 14 2.483V

Beyond this it gets into the receiver and transmitter.
Is there anything that you see out of the ordinary here? I dont, but the usb is nolonger responding to any computer. Is there anything else that you would like me to check? I assume that with the usb plugged in, I would see something on R12, R13 and R4. Also, do you know of anywhere that I can find what the voltage range should be for a component in this section of the board? Would there be a way to check u10, u11, u5, u7 and u8? Checking schematic now to see if I can tell which pins should have power. other than that, I dont know what to do at this point. Any advice would be helpful.

Thanks
David
dcochran
 
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Re: U4 blew

Postby AE9RB » Tue Mar 26, 2013 4:40 pm

Indeed, R12/R13 should be dividing the USB +5V. This isn't used to power the device, but simply to know when the USB cable is plugged in. It's possible a trace burned up during the short or the USB jack is damaged. Maybe the original problem was in the jack too.

If you have a USB cable you can cut up it will be easier to do the continuity tests on the jack and PCB.
73 David AE9RB
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Re: U4 blew

Postby dcochran » Tue Mar 26, 2013 5:12 pm

I removed u4 and USB works now. Unplugged until new u4 arrives and then I'll continue testing the sdr. Thanks for the input earlier. This kit is amazing.
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Re: U4 blew

Postby dcochran » Wed Mar 27, 2013 6:36 pm

I had some time to do some testing today. with U4 removed, power and USB plugged in I get the following

R12 - in 4.99V out 4.53V
R13 - in 4.53V out 0.9 mV
R4 - in 3.076V out 3.073V
R5 - in 9.1mV out 8.9mV Changes some. I assume this is because of the Capacitors at C59 and/or C61.

Does this look as expected?

Thanks again for the help.
dcochran
 
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Re: U4 blew

Postby dcochran » Fri Mar 29, 2013 3:43 am

U4 replaced. Also discovered USB was loose. That probably caused the issue. Cleaned it up and seems to be working now. Thanks!!
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