Is my raspberry unrepairable?

May I interject and offer an opinion here?

Consider the time taken to monitor this thread, probe the board and buy all the parts necessary to follow advice offered here.

How long before your costs (including an hourly rate) outweigh the value of what amounts to a throwaway computer?

One of the aims of the Raspberry Pi project was to put computers in the hands of children and were designed to be cheap to replace when careless hands did something that resulted in a dead board.

Greg

Greg, the time vs real dollars tradeoff can be very different for other people.

On the other hand, there is a learning experience which will be useful at a  later date but the value currently is unknown.

Mauricio: The LM1117-1.8 is a reaonsable LDO to make 1.8V from the 5V. Similarly the LM1117-3.3 is a good one for the 3.3V rail. In fact rpi-1 used one for the 3.3V rail. [update: And for the 1.8V rail as well!). Take care that you put the recommended capacitors near the LM1117. Check the datasheet for the VENDOR that you're using. TI might have other recommendations than ST for example.

Finding a place to inject 3.3V is easy: The GPIO will do fine.

Finding a place to inject 1.8V is more difficult. Hmm... Can you find C108, R57 and R58? Either side of R57 or C108 will do, but R58 being "not fitted" may be easier to solder to. (the other side of R58 is GND. Can you find C8 near there? One side is GND the other is 1.8V. Might be a lot bigger than the other ones.

Roger Wolff wrote:

 

A lab powersupply has a configurable current limit. This means that you can set that limit at say 30% above what you expect your circuit to use, and then not blow stuff up if there is a mistake in a circuit.

Yes, that is an extremely useful feature.  Another fun thing you can do with a lab supply is to clear a thin conductive bridge that's shorting together two signals because of a PC board defect.  You set your lab supply voltage to 0.5V or so and set the current way up to 10A or so.  Then you connect the leads to the two signals.  If the bridge is thin enough, the 10A will blow the bridge like a fuse and the 0.5V makes sure you don't apply too much voltage when the short clears.  This only works for some shorts, but when it works it rescues a board.

Absolutely. Did exactly that a week or two ago. Although my lab powersupply does not go any further than 3A, but it worked. :-)

Thanks for the info . On another notes, I took my meat thermometer to calculate the temperature of the chip and it reached up to 28°C (around 80°F).

Yea I'm definitively that kind of person xd i'll read more about batteries. Do you suggest me to power up them with an external battery, or can I desolder anything, or change the diodes?

28°C is kind of normal. The normal operation of the RPi CPU can get higher than this value.

The idea here is to use a 3.3V power supply capable of delivering at least a few amps. Then, by disconnecting the L1 (to disconnect the 3.3V switching regulator output) and using an external more powerful 3.3V power supply, you should be able to tell which chips are definitely fried. The faulty chips should get really hot (more than 60-80°C).

If the main CPU is fried, you might cut the PCB area with the switching power supply and use it for future projects whenever you need 3.3, 1.8 or 1.2V

Hi!

ok so at first, I tried to desolder it, and damn it was hard to, so I was scared to touch the others things around it. I ended up by breaking L1 carefully and then I was able to put some rosin core on it to make it easier for me to conduct things up. Can you tell me where am I supposed to join things? like the + and -  of the 3.3v battery.

I'm going to attache some photos. Would you be able to tell me if I did a good or if I did not x.x

Thanks!

The picture got rotated..

Before going any further, just make sure you have a regulated 3.3V supply (have a powerful 3.3V LDO on your battery so it will have enough amps to supply).

Now, put the "-" to any "GND" point on the board and the +3.3V to the upper part of the capacitor that filters the 3.3V rail (marked in orange).

Then, power up the board using a USB power adapter. The switching regulators will supply the 1.2V and the 1.8V rails.

Afterwards, connect your 3.3V power supply and check which chips are getting really hot.

Note that "really hot" is much hotter than the 28 degrees that I remember that you measured.

Sorry for late responding, hope you guys had a good holiday. So I followed your instructions; the hottest chip was smsc, then broadcom, and finally the elpida. The smsc actually gave me electric shock or something I might of touch something else but it really got hot and I felt an electric shock. the other two were pretty much the same as before.

http://elinux.org/R-Pi_Troubleshooting#Power_.2F_Start-up

Using a hot air gun, you can try to desolder the SMSC chip. Afterwards just make sure the pads on the PCB where the SMSC chip used to stay are clean and they don't make any shorts between them. Afterwards, you can try to power the board with all the voltages (1.2, 1.8, 3.3 and 5V) and see if the CPU is still functional.

Using a hot air gun, you can try to desolder the SMSC chip. Afterwards just make sure the pads on the PCB where the SMSC chip used to stay are clean and they don't make any shorts between them. Afterwards, you can try to power the board with all the voltages (1.2, 1.8, 3.3 and 5V) and see if the CPU is still functional.