Raspberry Pi Forums

I've went through R-Pi Troubleshooting page but didn't find answer.

My problem occurred probably when I've connected serial port USB adaptor to my Pi. I think I must have short-circuited something by mistake... it just switched off at some point.
Now, my Pi doesn't boot, as if it died. The only thing that indicates it might be still alive is a faint PWR light (not fully bright, as if 50% of its original brightness) and the CPU/GPU RAM is getting hotter and hotter as I keep the power source in the micro USB. I don't think the power source is the problem, as I've been using it for some time now, the same with two RPis.
Is it possible that the F3 polyfuse is "blown", or did my Pi die compeletly?

The PWR LED just comes from one of the voltage regulators.

1. That it is dim is a bad sign because it means at least one rail is abnormally low.

2. It never indicates that any of the CPU/GPU is actually working.

That the CPU/GPU/RAM is getting hot is another bad sign.

If the F3 polyfuse was 'blown' it wouldn't be able to supply enough current for the CPU/GPU/RAM to get hot.

I think your RPi is effectively dead (ie beyond your ability to repair). The GPIO pins are relatively 'fragile' in the electrical sense. Abusing them can be fatal.

well it might not help things that you've placed a bare pi on a slightly electrically conductive material such as an anti-static bag... just saying

It's certainly possible that the fuse is "blown" do you have a multimeter that you can use to check it with? While you're at it you might also want to check the voltage at TP1 and TP2.

Did this happen after you connected a specific device on the serial end or as soon as you plugged in the USB->Serial adapter?

drgeoff wrote:I think your RPi is effectively dead (ie beyond your ability to repair). The GPIO pins are relatively 'fragile' in the electrical sense. Abusing them can be fatal.

Oh, I had thought he meant he plugged in a usb->serial device into the Pi's USB port.

OP, can you clarify if you plugged in a USB->serial cable into the Pi's USB port, or if you attached a USB->Serial cable to the pi's GPIO pins?

abishur wrote:It's certainly possible that the fuse is "blown" do you have a multimeter that you can use to check it with? While you're at it you might also want to check the voltage at TP1 and TP2.

Unfortunately I haven't got a multimeter to check the voltage, so I cannot check it by myself.

abishur wrote:Did this happen after you connected a specific device on the serial end or as soon as you plugged in the USB->Serial adapter?

I think it happened (as I'm not fully sure) as I've plugged the serial adapter to my PC.

bubbl wrote:I think it happened (as I'm not fully sure) as I've plugged the serial adapter to my PC.

So this was connecting from a computer's USB port to the Pi's GPIO?

abishur wrote:So this was connecting from a computer's USB port to the Pi's GPIO?

Yes. I think I've done a bad thing, connecting GND to TXD by mistake on the Pi GPIO pins...

drgeoff wrote:I think your RPi is effectively dead (ie beyond your ability to repair). The GPIO pins are relatively 'fragile' in the electrical sense. Abusing them can be fatal.

ahhh... I'm afraid it is... time to get a new one...

bubbl wrote:

abishur wrote:So this was connecting from a computer's USB port to the Pi's GPIO?

Yes. I think I've done a bad thing, connecting GND to TXD by mistake on the Pi GPIO pins...

Yes, you've done a bad thing, I'm sorry (I'm so, so sorry)(Good ol' #10). The issue might have actually been that the serial adapter you have, uses 5V logic. You have to specifically purchase a serial device that operates at 3v3 logic to match what the GPIO pins can handle as the 5v serial adapters will blow your pi up.

abishur wrote:

bubbl wrote:

abishur wrote:So this was connecting from a computer's USB port to the Pi's GPIO?

Yes. I think I've done a bad thing, connecting GND to TXD by mistake on the Pi GPIO pins...

Yes, you've done a bad thing, I'm sorry (I'm so, so sorry)(Good ol' #10). The issue might have actually been that the serial adapter you have, uses 5V logic. You have to specifically purchase a serial device that operates at 3v3 logic to match what the GPIO pins can handle as the 5v serial adapters will blow your pi up.

it does have 3.3V logic as well as 5V. might have been faulty one..
now i've noticed the F3 and D17 near mini USB are heating up as well. after some time the Pi switches off automatically.

bubbl wrote:now i've noticed the F3 and D17 near mini USB are heating up as well. after some time the Pi switches off automatically.

If the PSU is within spec (never goes above 5.25 volts) then D17 should NEVER conduct ANY current even if every other component on the board is totally fried. A component cannot generate heat if no current is passing though it. Are you sure it isn't the regulator RG2 on the other side of the board which is getting hot?

drgeoff wrote: Are you sure it isn't the regulator RG2 on the other side of the board which is getting hot?

I'm not sure. Everything there gets hot. The other side with RG2 as well. If it's RG2, might the Pi be rescued?

bubbl wrote:

drgeoff wrote: Are you sure it isn't the regulator RG2 on the other side of the board which is getting hot?

I'm not sure. Everything there gets hot. The other side with RG2 as well. If it's RG2, might the Pi be rescued?

No, RG2 gets hot when it is asked to deliver too much current .... usually by a fried SoC.

drgeoff wrote:No, RG2 gets hot when it is asked to deliver too much current .... usually by a fried SoC.

Thanks for the reply. next time I'll be more careful...