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MeisterKN
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Re: LEDs

Sun Mar 27, 2016 5:44 pm

Anyone notice number 13342 on top of USBs in the pictures. What does this number mean? What is the drawing next to it. I have seen these additional codes that PC Technicians use when refurbishing a computer or providing any sort of final checks in post production. Just wandering.
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MeisterKN
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Re: LEDs

Sun Mar 27, 2016 5:53 pm

See the number 13342 on top of USBs plus a drawing. Anyone has an idea what these two represent. I have googled and there is a post in this forum with an address viewtopic.php?t=1470&p=13342
How to fix broken software
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Re: LEDs

Mon Mar 28, 2016 2:42 am

MeisterKN wrote:See the number 13342 on top of USBs plus a drawing. Anyone has an idea what these two represent. I have googled and there is a post in this forum with an address viewtopic.php?t=1470&p=13342
How to fix broken software
I have 13263 on one of my B+ USBs, probably a batch number.

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Re: LEDs

Mon Mar 28, 2016 7:06 am

by Rassilon216 » Sat Jun 08, 2013 4:27 pm
My raspberry pi is overheating extremely fast after startup. I notice that yesterday when I was trying to figure out the GPIO pin stuff, I looked and the pi was extremely hot and had shut down. Within half a minute of booting, the pi overheats to 140ºF and shuts down. Any ideas?

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viewtopic.php?f=28&t=46521
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Re: LEDs

Mon Mar 28, 2016 7:08 am

"within half a minute....(it) shuts down"
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rurwin
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Re: LEDs

Mon Mar 28, 2016 9:54 am

I was trying to figure out the GPIO pin stuff, I looked and the pi was extremely hot and had shut down. Within half a minute of booting, the pi overheats to 140ºF and shuts down.
That must have been one of the first threads that showed that shorting out GPIO pins while the Pi was switched on could cause a thermal cascade and break the whole thing.

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Re: LEDs

Tue Mar 29, 2016 4:37 am

This morning I unplugged all peripherals and connected the Pi to power. After 7 seconds the CPU/GPU/RAM CHIP started quickly heating up to have had reached temperature very hot to touch (basically you have to remove your hand away: I do not have anything to measure temp but this was very hot) within another 10 seconds. Quickly the whole left half of the board (starting from around power-in) became as hot as the CPU. So CPU first, than the whole left side of the board. The red light turned off after about 35 seconds.

After the light turned off, the board became quickly colder. This means there is a switch which turns off the Pi when there is an increase in temperature and NOT knowing if there is a short, otherwise it would turn off the device after 1-2 seconds, or it wouldn't start it at all. However this also means the Pi is not dead, it only heats up too much.

Are we 100% certain this is caused by a short and not some other problem in Pi like a CPU failure (knowing it is the one that heats up first) ?????!!!!!?????!!!!!!!

To look for shorts with a multimeter might be a tedious process, as even the conducting thin golden lines have to be measured. Any voltage would indicate OK I guess. However, I only have 30 seconds to measure. I guess you cannot look for a short without power supply??!!! Can I?

Here is a link that many have used to fix circuits.
http://www.circuitrework.com/guides/guides.shtml
I will read it throughout the day. A question so far (I am sure I will have many as I read through this valuable reading and guaranteed for accurateness) : Is Raspberry Pi :

Class 1 General Electronic Products
Class 2 Dedicated Service Electronic Products
Class 3 High Performance Electronic Products

It is not printed on the board which class...

Second, there is a shortsniffer hardware unit (costs around 200 USD)
Check out the site.
http://www.testecvw.com/
I guess it would be useful to have this toy in my profession (Comp Technician ++++++ IT and computer science ++++++ Programming++++++Web design) as you do get supposedly dead motherboards and "cards" which might only have a short. In 1996, we used to take a card and re-solder all soldered parts, as an exercise I thought was silly and couldn't even today find 100% clear explanation in my head as to why we did this with the service having around 20 computers ready for repair.

NOW, How do you fix a short on a circuit such as Raspberry Pi?
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Re: LEDs

Tue Mar 29, 2016 5:06 am

MeisterKN wrote:Are we 100% certain this is caused by a short and not some other problem in Pi like a CPU failure (knowing it is the one that heats up first) ?????!!!!!?????!!!!!!!
I think you missed the point.

A brief short of a GPIO pin can cause the SoC (CPU/GPU chip) to fail internally. This will cause it to overcurrent and over heat. After a while the fuse will blow, thus cutting off the power and the LED going out. After some time switched off, the fuse will recover. The SoC won't.

There is no point in looking for a short on the board, because there probably isn't one now. Also you wouldn't be able to test all the layers of the board anyway.

Your Pi is dead.

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Re: LEDs

Tue Mar 29, 2016 3:44 pm

You are right. I did not understand that the short was brief and thought it might have caused a permanent "break" in current flow.
However if the CPU overheats again and again as I connect power, it can not be dead or as you say "...it will not recover...".

Basic logic will tell you that if something overheats it IS NOT DEAD, electronically speaking, and probably does not have any failure AT ALL. The overheating being explained as something allowing more current to it (or some other problem).

Something else is dead..., COLD dead! This could be a shortage.
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Re: LEDs

Tue Mar 29, 2016 4:00 pm

OK, it's not dead, but it's dying and there's nothing you can do to keep it alive.

As far as we understand, not being privy to the wafer design, the process goes like this:
  1. Some GPIO pin is exposed to 5V. This breaks something in the circuitry of the port.
  2. Because of the broken bit, the port takes too much current and overheats.
  3. Because of the localised heating, more stuff breaks.
  4. More stuff takes more current, leading to more heating over an expanded area of the die.
  5. More heating leads to more breakage.
  6. More breakage leads to more heating,
  7. Repeat until death.
During that process the SoC continues to work. Or at least those parts that are not broken do. But the increased heating causes it to shutdown and that happens more quickly the further the fault spreads.

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Re: LEDs

Tue Mar 29, 2016 5:18 pm

The RPi 2 has a 2.0A polyfuse. When the current goes above 2.0A for any reason then the fuse begins to heat up and increase in resistance.
The more current flow the higher the resistance so the voltage and current are shut off after a few seconds. There is an infinite number of possible fault conditions inside the SOC which that cause the high current flow. The poly type fuse will self heal if left powered down for a period of time (several hours). If the fuse were not there then likely the SOC would smoke or even erupt into flame.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

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Re: LEDs

Tue Mar 29, 2016 9:20 pm

The poly-switch (fuse) does not explain the symptoms. If the Pi is powered down for a few seconds then it will run again for a while. If the poly-switch had triggered it would not run again for several minutes, certainly not seconds.

I think it is more likely that the over-heating is triggering the internal thermal shutdown of the SoC. We know it throttles when the temperature goes over 85C, but there's another limit at which it shuts down entirely.

There's another possibility that the SoC is trying to use areas of the chip that are already damaged. Errors from these attempts accumulate to cause a catastrophic crash some minute or so after boot.

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Re: LEDs

Wed Mar 30, 2016 8:59 pm

rurwin wrote:The poly-switch (fuse) does not explain the symptoms. If the Pi is powered down for a few seconds then it will run again for a while. If the poly-switch had triggered it would not run again for several minutes, certainly not seconds.
Have you actually tried that? Years ago I experimented with tripping the fuse by holding 5V across it for up to a minute. The basic recovery time was faster than I could easily measure. Maybe even less than one second; certainly not minutes.

It is easy to test if the fuse has tripped by measuring the voltage across it after the red power LED goes out. The fuse can be bypassed, but then as kiricks points out there is a significant risk of fire. A Pi drawing excessive current continuously could also permanently damage the power supply.

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Re: LEDs

Thu Mar 31, 2016 2:08 pm

MeisterKN wrote:Basic logic will tell you that if something overheats it IS NOT DEAD, electronically speaking, and probably does not have any failure AT ALL. The overheating being explained as something allowing more current to it (or some other problem).
No, the problem is more likely some fault condition within the SoC is causing it to draw more current than it should which causes excess heating.

It may not be technically dead, but it's not healthy either. It is dying and will die eventually. There is unlikely any way you can make it healthy again.

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Re: LEDs

Fri Apr 01, 2016 4:44 am

I have been doing some work, research and work again. First, the voltage regulator, RG2, shows the power of 4.56 V input, and 2.5 V as the output. So, there is a drop in voltage, not an increase.

Today, I did not measure any current flow, however this is not important at this time.

Second there is a proportionate drop in voltage across both R1 and R3 regulators (R stands for resistor in electronics, how could they use this notation for some "regulators"), all three not giving me any headache as all parts require some voltage and as soon as

Third: the fuse RECOVERS (it currently measures 4.5 V) It has to go back to 5 V. I just haven't given it (the fuse) enough time, not realising that it is still recovering while the RED LED is OFF. This being so because it is the only part which remains hot after the red LED turns off.

Fourth, I tried to perform a hardware reset by using a normal piece of wire to short the PIN 6, 1 and 2 together. This did not work (I WANDER WHY) as the red LED remained and the old, already mentioned processes occurred regardless. I might have used wire too thick to conduct such low level of power.

The Pi is obviously not dead nor dying, as some have been quick to suggest. Now, I will wait up to a week, having the Pi powered up (this long it may take to bring it back to 5 V).
There is a so called "cowboy" method (crossing a wire across the fuse to kick start it, as it is highly not recommended, and I can not be bothered to work on such small chips.

It is my opinion in general that for there to be an unrecoverable short there has to be burning and smelling and no LEDs working at all, then, cold and "kaput".

Overall, what bugs me is how can a LOWER voltage cause the left half of Pi to heat up including all components (except the GPIO pins which are normal temp.), and the right side to remain normal (lukewarm to cold).
Second, even though the red POWER LED is off, the fuse is still receiving high voltage.

Even though it is stated that even smallest drops in power (V) can cause some chips to behave abnormal, it is of no concern here as the fuse input equals the regulator input, approx 4.5 V.

Also, I once used a China shop charger 9 V as I researched that the second monitor requires 9 Volts to operate (failed to operate as it is still questionable whether this automobile monitor is compatible with the pi at all - Is there anyone who ran it with success?)
This is what might have wanked the fuse.
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Re: LEDs

Fri Apr 01, 2016 6:45 am

MeisterKN wrote:The Pi is obviously not dead nor dying, as some have been quick to suggest.
Nothing that you have posted contradicts the prevailing theory that your Pi is damaged beyond repair.

The red LED goes out because your 3.3V rail is collapsing. (Note to others: this is a Pi 1B.) Theoretically that could be due to a fault with RG2, or F1, or any component that connects across 3.3V. Replacing the failed component may fix it. However, the fact that IC2 is the first thing to get hot makes it clear that the excess current draw is inside the main system chip, probably in the GPIO circuitry. You cannot repair or replace that chip, so your Pi is useless.

Your plan to keep the polyfuse in its tripped state for as long a possible does not make any sense. I cannot recommend bridging the fuse either, because I do not think you understand the risks. At the moment you do not know how much fault current is being drawn, or what temperatures might be reached.

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Re: LEDs

Fri Apr 01, 2016 12:27 pm

1.) No one has measured any current flow yet
2.) Having the device plugged into power in this state all day today from 6:00 A.M. to 14:20 P.M. has two positive results:
a.) the green LED has returned after being gone for 20 days of occasional probes
b.) no increase in temperature, and no further problems
3.) In computers, you don't know obviously, the first chip accessed after CMOS is the processor, i.e. that why it heats first.
4.) Low voltage usually spells low current

@ jojopi
How old are you?
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Re: LEDs

Fri Apr 01, 2016 12:43 pm

I would like to hear from breakie12 as this member was closest to what I have discovered later. I have actually started work on the fault few days ago, when I registered. Thought I would get some practical advice, but the only conclusion reached is, in fact, you can hardware reset Raspberry Pi, Model B, Rev. 2.0, by placing (perhaps a few telephone (thin)) wires across pin 6 pin 1 and pin 2. I do not have the means to build a switch at this location on the board.
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Re: LEDs

Fri Apr 01, 2016 12:55 pm

MeisterKN wrote:...most important point against "self"-mutilation argument, is, that, there are no burned, black, broken, or damaged pins, joints, or any parts on the board...
False assumption.
...placing the monitor in all possible positions on top of pins to see if it will give any response...
You've clearly blown it up. Why can't you just accept this and move on?
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Re: LEDs

Fri Apr 01, 2016 6:51 pm

MeisterKN wrote:Thought I would get some practical advice, but the only conclusion reached is, in fact, you can hardware reset Raspberry Pi, Model B, Rev. 2.0, by placing (perhaps a few telephone (thin)) wires across pin 6 pin 1 and pin 2.
So, connect the 3.3V and 5V and GND pins together, thus shorting out everything, blowing the fuse and probably destroying every important part of the Pi in the process.

It's just as well I checked the date before taking your post seriously :lol:

You can't fool me! :D

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Re: LEDs

Sat Apr 02, 2016 6:53 am

@ GTR2Fan

What ever the case, issue, or, outcome is with the device, why would anyone lose patience in anticipation of some kind of closure?


@ rpdom

PIN 6 is not what you imagine it to be. It is the two holes next to RG2 sometimes referred to as pin 1 and pin 2. Its code on the board is P2 D2. When you join them together you perform a hardware reset. Some people buy pins like the GPIO pins (you need two) and make themselves a switch for resetting Pi any time with ease.

What date are you referring to?

What possible benefit do you propose I would have from fooling anyone about this annoying fault on the board?
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Re: LEDs

Sat Apr 02, 2016 7:08 am

MeisterKN wrote:PIN 6 is not what you imagine it to be. It is the two holes next to RG2 sometimes referred to as pin 1 and pin 2. Its code on the board is P2 D2. When you join them together you perform a hardware reset. Some people buy pins like the GPIO pins (you need two) and make themselves a switch for resetting Pi any time with ease.
If you mean the P6 header, why don't you refer to it as that, rather than making up a confusing naming convention of your own :roll:

On later boards it is referred to as the RUN header, but that's not important now I understand what you are talking about.

You still need to accept that your Pi has had it's day and your only choice is to replace it.

The overheating chips and regulators indicate that there is a short circuit somewhere that is draining the current, overloading the fuse and probably the PSU too.

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Re: LEDs

Sun Apr 03, 2016 10:04 am

Thanks for all your answer. As I mentioned earlier I am in the process of buying a newer Raspberry Pi, maybe Pi2, maybe Pi 3.
It seems you are right. If the short is within the CPU, it is not financialy viable to replace, so in those terms, this piece of hardware is dead.

I conclude my research and hope to visit the forum with more interesting issues in the future.

I am pleased with the results.
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