netlinker
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Spare BMC2837

Mon Aug 26, 2019 9:23 am

Hi everyone,

just recently I destroyed two of my beloved RPI 3B. It seems, Overvoltage, comming from the HDMI out, destroyed the processors.
Sadly I only got suspicious after the second one died within a week.
I have a one pole switch installed prior to my Monitor to fully switch it of, when I don't need it. The problem seems to be, that the switch was installed in such a way that it only cuts ground and not the phase (this is possible with the german and european power sockets). This somehow lead to undesired voltages at the HDMI input which destroyed my PIs as the stb supply of the monitor was floating 230Volts above ground. Usually this should not lead to any damage (isolating powersupply), but capacitive currents seem to have been enough to slowly (~1 Day) kill my PIs :( .
As I now have two dead PIs and I'm a skilled electronics person, I would like to rework the two PIs (not that difficult as its not even POP as the zero). In order to do this, I would have to source two spare processors.
Is there any chance of getting those somewhere?

greetings

netlinker

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DougieLawson
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Re: Spare BMC2837

Mon Aug 26, 2019 9:41 am

They aren't available in quantities of less than 1,000,000 per order from Broadcom.

The price of that will far exceed £35 for a new RPi.
Note: Having anything humorous in your signature is completely banned on this forum. Wear a tin-foil hat and you'll get a ban.

Any DMs sent on Twitter will be answered next month.

This is a doctor free zone.

andrum99
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Re: Spare BMC2837

Mon Aug 26, 2019 10:25 am

netlinker wrote:
Mon Aug 26, 2019 9:23 am
I have a one pole switch installed prior to my Monitor to fully switch it off
Don't do that. Switched wall outlets are all 2 pole now for a good reason. Also, why were you switching the neutral wire? Single pole switches are meant to be connected to the live wire.
Last edited by andrum99 on Mon Aug 26, 2019 12:59 pm, edited 1 time in total.

LTolledo
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Re: Spare BMC2837

Mon Aug 26, 2019 10:28 am

Buy a new one and save yourself the trouble, and possible frustrations.

Its more economical and practical to get a brand new one than doing repairs....

as for the broken/busted RPis, I suggest you put it in a picture frame and use it as a decor in your workshop.... as a reminder of previous mistakes (so as not to repeat those again)
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

hippy
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Re: Spare BMC2837

Mon Aug 26, 2019 10:58 am

netlinker wrote:
Mon Aug 26, 2019 9:23 am
I have a one pole switch installed prior to my Monitor to fully switch it of, when I don't need it. The problem seems to be, that the switch was installed in such a way that it only cuts ground and not the phase (this is possible with the german and european power sockets).
I am guessing you mean it only switches neutral as switching ground would have no effect on powered equipment if properly wired.

Switching neutral only is not a good idea but I cannot see how doing so would create a voltage differential which would damage the Pi.

I am not convinced "the stb supply of the monitor was floating 230Volts above ground" or that "capacitive currents" via HDMI would damage the Pi.

drgeoff
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Re: Spare BMC2837

Mon Aug 26, 2019 12:39 pm

andrum99 wrote:
Mon Aug 26, 2019 10:25 am
Switched wall outlets are all 2 pole now for a good reason.
If that is the case in the UK it is news to me.

andrum99
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Re: Spare BMC2837

Mon Aug 26, 2019 12:59 pm

drgeoff wrote:
Mon Aug 26, 2019 12:39 pm
andrum99 wrote:
Mon Aug 26, 2019 10:25 am
Switched wall outlets are all 2 pole now for a good reason.
If that is the case in the UK it is news to me.
They are two pole now as standard. There can be non-zero voltages present on the neutral wire, so it's a good idea to have both isolated by the switch.

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rpdom
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Re: Spare BMC2837

Mon Aug 26, 2019 1:18 pm

andrum99 wrote:
Mon Aug 26, 2019 12:59 pm
drgeoff wrote:
Mon Aug 26, 2019 12:39 pm
andrum99 wrote:
Mon Aug 26, 2019 10:25 am
Switched wall outlets are all 2 pole now for a good reason.
If that is the case in the UK it is news to me.
They are two pole now as standard. There can be non-zero voltages present on the neutral wire, so it's a good idea to have both isolated by the switch.
I've not seen any two-pole switched sockets available yet (I'll have to ask the electrician over the road from me if he has). Neutral is usually bonded to Earth at some point, so shouldn't have any voltage on it - but it depends where that is measured relative to. Most PSUs should be isolated from the mains so it shouldn't matter which side they are switched from, but many of them have a capacitor between the input and output sides that can cause a voltage differential.

drgeoff
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Re: Spare BMC2837

Mon Aug 26, 2019 2:36 pm

Don't know if they are now standard and mandated by the IET Wiring Regulations but DP switched wall sockets do indeed exist. https://mkelectric.presti.media/uk/#page/12-13

Not necessary to my way of thinking. The purpose of the switch on a wall outlet is to prevent an appliance operating. A single pole switch is adequate for that. For isolation purposes (equipment being worked on) the plug should be pulled out. Never rely on a wall socket switch for that, irrespective of single or double pole.

netlinker
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Re: Spare BMC2837

Tue Aug 27, 2019 7:50 am

Yes indeed, I meant "neutral".
Its a pluggable switch like that kind you can plug inbetween the outlet and your device. In the UK you can't reverse the Plug (at least the three pole version), because its coded, in Germany you can. Therefore you won't know if it is switching neutral or phase.
I bought it from some electronics distributor here in Germany thinking it would switch both lines. Well it turned out it didn't.

I'm still investigating the cause for the damage tough. Does anybody know if the HDMI output is protected by some kind of TVS circuit, and if so, what the absolute maximum ratings are?

Sad that there is no shop for small quantity BCM 2837. The Pi would be so easy to repair with just a few parts on it. :(

trejan
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Re: Spare BMC2837

Tue Aug 27, 2019 8:33 am

netlinker wrote:
Tue Aug 27, 2019 7:50 am
I'm still investigating the cause for the damage tough. Does anybody know if the HDMI output is protected by some kind of TVS circuit, and if so, what the absolute maximum ratings are?
No additional TVS. The SoC does have ESD protection on those pins but don't know the ratings. Your 3B has some common mode filters as well.

fruitoftheloom
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Re: Spare BMC2837

Tue Aug 27, 2019 8:39 am

netlinker wrote:
Tue Aug 27, 2019 7:50 am
Yes indeed, I meant "neutral".
Its a pluggable switch like that kind you can plug inbetween the outlet and your device. In the UK you can't reverse the Plug (at least the three pole version), because its coded, in Germany you can. Therefore you won't know if it is switching neutral or phase.
I bought it from some electronics distributor here in Germany thinking it would switch both lines. Well it turned out it didn't.

I'm still investigating the cause for the damage tough. Does anybody know if the HDMI output is protected by some kind of TVS circuit, and if so, what the absolute maximum ratings are?

Sad that there is no shop for small quantity BCM 2837. The Pi would be so easy to repair with just a few parts on it. :(

The board is multi layer and I doubt you could successfully replace the SoC.

If you could buy the SoC then anyone could "manufacture" a Raspberry Pi compatible SBC, and then the end of RPT / RPF existence.

Surely it would be better not to waste $35 by destroying your boards ?
Retired disgracefully.....

hippy
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Re: Spare BMC2837

Tue Aug 27, 2019 11:59 am

netlinker wrote:
Tue Aug 27, 2019 7:50 am
Sad that there is no shop for small quantity BCM 2837. The Pi would be so easy to repair with just a few parts on it. :(
But you don't actually know what has been damaged, so you would ideally want to replace everything which could have been damaged, and then you might as well just buy a new board.

W. H. Heydt
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Re: Spare BMC2837

Wed Aug 28, 2019 2:54 am

netlinker wrote:
Tue Aug 27, 2019 7:50 am
Sad that there is no shop for small quantity BCM 2837. The Pi would be so easy to repair with just a few parts on it. :(
For some values of "easy"...

You could always inquire if Broadcom would sell you only a couple of hundred thousand and then go into the retail business, peddling them...

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bensimmo
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Re: Spare BMC2837

Wed Aug 28, 2019 8:07 am

You can still buy and use single pole in the UK. Just look on Screwfix.
Even for new builds.


Anyway

Are you sure it the SoC and not the power circuit? I'm interested how you know (to learn)

I don't doubt it is easy for you to do, you say you have the skills :-)
I don't know why others do.

Put a request out for people who have dead Pi3 for whatever reasons.

netlinker
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Re: Spare BMC2837

Wed Aug 28, 2019 8:14 am

trejan wrote:
Tue Aug 27, 2019 8:33 am
netlinker wrote:
Tue Aug 27, 2019 7:50 am
I'm still investigating the cause for the damage tough. Does anybody know if the HDMI output is protected by some kind of TVS circuit, and if so, what the absolute maximum ratings are?
No additional TVS. The SoC does have ESD protection on those pins but don't know the ratings. Your 3B has some common mode filters as well.
OK, I'll check that. Thermal Images show the SOC lighting like a christmas tree tough (>100°C). So either there is a output on the SOC with a tremendous amount of load (unlikely in my opinion), or the chip is broken.
fruitoftheloom wrote: The board is multi layer and I doubt you could successfully replace the SoC.

If you could buy the SoC then anyone could "manufacture" a Raspberry Pi compatible SBC, and then the end of RPT / RPF existence.

Surely it would be better not to waste $35 by destroying your boards ?
I agree that it would have been better not to destroy the boards, but hey, who wants to destroy his SBC?

Swapping a BGA chip is no big deal. I can't see any problem doing so. All you need is a reballing set (which I have), a hotplate for preheat (which I have) and a hot air soldering machine (which I have).

I doubt that anybody could create knock offs of the pi if they Limit the chips to 5 per customer per year or something. Anyway, in order to be cheaper than the 35$ you would have to do thousands of them per year if you could make it at all. Designing and manufacturing such a complex PCB is not trivial. You don't want do do this at home, as the price per piece would easily exceed 100€ + working time. In my opinion, nobody would be insane enough to try to copy a RBP if they can't source the components in VERY large numbers.
hippy wrote: But you don't actually know what has been damaged, so you would ideally want to replace everything which could have been damaged, and then you might as well just buy a new board.
Thats right, I can't tell for sure, but I know the powersupply is still working and nothing else is getting exceptionally hot (checked with thermal camera, best friend of a repairsman ;) ). This is a 90% sign, that those components are still intact.
W. H. Heydt wrote: For some values of "easy"...
You could always inquire if Broadcom would sell you only a couple of hundred thousand and then go into the retail business, peddling them...
:lol: yes, indeed, but I doubt my storage space would be enough for this.
Actually I hoped the RPF would someday sell spare parts, at least the kind you won't get on Mouser or Digikey.
BTW money is not the driving force behind this (I could barely work an hour on the money I save by repairing them). It's just an attempt to have two single board computers less of electronics scrap on the world.

netlinker
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Re: Spare BMC2837

Wed Aug 28, 2019 8:26 am

bensimmo wrote:
Wed Aug 28, 2019 8:07 am
You can still buy and use single pole in the UK. Just look on Screwfix.
Even for new builds.


Anyway

Are you sure it the SoC and not the power circuit? I'm interested how you know (to learn)

I don't doubt it is easy for you to do, you say you have the skills :-)
I don't know why others do.

Put a request out for people who have dead Pi3 for whatever reasons.
When you have a broken electronics device, there are several things you check:
1. when did the failure happen? Do you know the exact circumstances (I plugged in a new monitor and it broke (after 2 Days). It ran 2 years without any problems before, very suspicious.
2. Is the power supply still working? Check the 5V rail (working). Check the 3.3V rail (working but breaks down to 1 Volt from time to time).
3. Search the reason for the breakdown ... check power draw of the board.
4. Regulator is staying cold and is in current limit mode (draws constant current from 5V, but output is breaking down)
5. There must be a high load on the 3.3V rail (roughly 2 Watt in my case) -> search for it -> found only CPU getting really hot.
6. Supply 3.3V rail with a current limited bench top power supply, check if you can pull it up. Half an amp more on the rail showed no difference, but the CPU getting hotter. -> most probably CPU is dead.
I think it fried the HDMI driver. Probably, but just probably it is possible to unsolder the CPU, cut the power source for the HDMI block if it is externally accessible on the package (which I don't know) and hope for the rest to be still functional. But this is in my opinion not worth the effort as the chances of it working are really low. That's maybe something for a rainy Sunday afternoon.

I hope this is what you asked for.

hippy
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Re: Spare BMC2837

Wed Aug 28, 2019 10:20 am

netlinker wrote:
Wed Aug 28, 2019 8:14 am
Swapping a BGA chip is no big deal. I can't see any problem doing so. All you need is a reballing set (which I have), a hotplate for preheat (which I have) and a hot air soldering machine (which I have).
I would suggest buying another Pi 3B, unsoldering the SoC from that, replacing the damaged one, filming and photographing everything as you go.

That would make it a $35 replacement SoC but the publicity and kudos you get from having done it and documenting it will likely more than compensate. It would also give you a 'claim to fame' which should sit well on any CV.

It would even put you in a good position to ask for a replacement SoC at a reasonable price to bring the donor board back to life.

And, having done it, returned a dead Pi back to life, there would even be an opportunity for a side-line business providing that service for those who cannot do it themselves. You could perhaps become the Foundation's first authorised board repairer if you wanted that.

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rpdom
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Re: Spare BMC2837

Wed Aug 28, 2019 10:52 am

hippy wrote:
Wed Aug 28, 2019 10:20 am
netlinker wrote:
Wed Aug 28, 2019 8:14 am
Swapping a BGA chip is no big deal. I can't see any problem doing so. All you need is a reballing set (which I have), a hotplate for preheat (which I have) and a hot air soldering machine (which I have).
I would suggest buying another Pi 3B, unsoldering the SoC from that, replacing the damaged one, filming and photographing everything as you go.

That would make it a $35 replacement SoC but the publicity and kudos you get from having done it and documenting it will likely more than compensate. It would also give you a 'claim to fame' which should sit well on any CV.

It would even put you in a good position to ask for a replacement SoC at a reasonable price to bring the donor board back to life.

And, having done it, returned a dead Pi back to life, there would even be an opportunity for a side-line business providing that service for those who cannot do it themselves. You could perhaps become the Foundation's first authorised board repairer if you wanted that.
Indeed. One repair I can think of that might help some people is to replace the PMIC chip on the 3B+ when it fails. I think JamesH said there might be an opportunity for buying those chips in quantities of 100 perhaps. Quite a few people have reported having that issue. A little bit easier than replacing the SoC, but beyond the skills of many hobbyists I think. Or even sell the chips on individually to those who believe they can replace it, but are unable to get the part.

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bensimmo
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Re: Spare BMC2837

Wed Aug 28, 2019 2:40 pm

netlinker wrote:
Wed Aug 28, 2019 8:26 am
bensimmo wrote:
Wed Aug 28, 2019 8:07 am
You can still buy and use single pole in the UK. Just look on Screwfix.
Even for new builds.


Anyway

Are you sure it the SoC and not the power circuit? I'm interested how you know (to learn)

I don't doubt it is easy for you to do, you say you have the skills :-)
I don't know why others do.

Put a request out for people who have dead Pi3 for whatever reasons.
When you have a broken electronics device, there are several things you check:
1. when did the failure happen? Do you know the exact circumstances (I plugged in a new monitor and it broke (after 2 Days). It ran 2 years without any problems before, very suspicious.
2. Is the power supply still working? Check the 5V rail (working). Check the 3.3V rail (working but breaks down to 1 Volt from time to time).
3. Search the reason for the breakdown ... check power draw of the board.
4. Regulator is staying cold and is in current limit mode (draws constant current from 5V, but output is breaking down)
5. There must be a high load on the 3.3V rail (roughly 2 Watt in my case) -> search for it -> found only CPU getting really hot.
6. Supply 3.3V rail with a current limited bench top power supply, check if you can pull it up. Half an amp more on the rail showed no difference, but the CPU getting hotter. -> most probably CPU is dead.
I think it fried the HDMI driver. Probably, but just probably it is possible to unsolder the CPU, cut the power source for the HDMI block if it is externally accessible on the package (which I don't know) and hope for the rest to be still functional. But this is in my opinion not worth the effort as the chances of it working are really low. That's maybe something for a rainy Sunday afternoon.

I hope this is what you asked for.
Yes, thankyou :-)

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davidcoton
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Re: Spare BMC2837

Wed Aug 28, 2019 9:36 pm

bensimmo wrote:
Wed Aug 28, 2019 8:07 am
You can still buy and use single pole in the UK. Just look on Screwfix.
Even for new builds.
Correct. There are three types of 13A socket available in the UK -- unswitched, single pole switched, and double pole switched.
All are "legal" and all are permitted under the 18th Edition Wiring Regs.
As long as the wiring is correct, all of these are safe. If the wiring is wrong, none are safe.

AFAIK the only two-pin, 5A sockets now available in the UK are the isolated types for use in bathrooms. Non-isolated types have been available in the past and can present the type of problem described by the OP when powering anything other than non-interconnected Class II equipment.
Signature retired

netlinker
Posts: 9
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Re: Spare BMC2837

Fri Aug 30, 2019 12:22 pm

Ok everyone,

I managed to bring one of my broken boards back to life. Here is what I did:
1. Measure shorts on the powerrails -> found short on 3.3V (1 Ohms)
2. Locate short -> use a high resolution ohmmeter and measure the resistance of the short at all 3.3V points accessible.
3. The point with the lowest resistance was the blocking capacitor for 3.3V HDMI supply.
4. Make sure where to cut the connection to the HDMI 3.3V Pad. -> Via next to blocker
5. Cut via from 3.3V in a way that can be reverted.
6. Check for short on 3.3V -> gone :D
7. Try Pi -> booting and reporting to network. No issues found with journalctl
8. Check state of HDMI output -> to be done

I know I announced this for a misty Sunday, but I just couldn't resist. :lol:

Kudos go to two people making this possible:
Gilles Read for the X-Ray: https://www.flickr.com/photos/ultrapurple/25313223701
AndrewS for the Pinout: https://elinux.org/RPi_BCM2837_Pinout

Without those two sources I would have had a hard time guessing.

Right now I don't have a monitor to test the status of the HDMI output, but I would guess it is not functional anymore.
Pictures of the procedure will follow soon.
At least now I have a working Pi 3B for headless applications.
I will check if I can repair the second one the same way.

Unfortunately I didn't find the cause for the two PIs breaking. I checked the HDMI input of the suspicious monitor and could not find anything that would damage a PI. No high voltages, no groundloops. I'm open for suggestions on what to test. My next step is to check the behaviour of the monitor on powerup and powerdown.
rpdom wrote: Indeed. One repair I can think of that might help some people is to replace the PMIC chip on the 3B+ when it fails. I think JamesH said there might be an opportunity for buying those chips in quantities of 100 perhaps. Quite a few people have reported having that issue. A little bit easier than replacing the SoC, but beyond the skills of many hobbyists I think. Or even sell the chips on individually to those who believe they can replace it, but are unable to get the part.
Yes that would be easy to do. I'm not sure about the economics of this procedure. I would have to give it a try and check the repair time.
hippy wrote:
netlinker wrote:
Wed Aug 28, 2019 8:14 am
Swapping a BGA chip is no big deal. I can't see any problem doing so. All you need is a reballing set (which I have), a hotplate for preheat (which I have) and a hot air soldering machine (which I have).
I would suggest buying another Pi 3B, unsoldering the SoC from that, replacing the damaged one, filming and photographing everything as you go.

That would make it a $35 replacement SoC but the publicity and kudos you get from having done it and documenting it will likely more than compensate. It would also give you a 'claim to fame' which should sit well on any CV.

It would even put you in a good position to ask for a replacement SoC at a reasonable price to bring the donor board back to life.

And, having done it, returned a dead Pi back to life, there would even be an opportunity for a side-line business providing that service for those who cannot do it themselves. You could perhaps become the Foundation's first authorised board repairer if you wanted that.
Swapping the SOC from another PI is indeed a way to go. Maybe someone has one lying around with something else broken?
Making some videos of this is also a good idea. I wanted to create a youtube channel featuring such stuff anyway. I have to check if I can find the time though.

trejan
Posts: 720
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Re: Spare BMC2837

Fri Aug 30, 2019 1:20 pm

netlinker wrote:
Fri Aug 30, 2019 12:22 pm
Swapping the SOC from another PI is indeed a way to go. Maybe someone has one lying around with something else broken?
Not sure how easy it will be to find a broken 3B that didn't die from damage to the SoC. You might be able to get a BCM2837B0 from a 3B+ with a dead PMIC and put that into your 3B. New 3B boards have changed to using a BCM2837B0 now but I've never actually seen one. No idea if there are other changes needed though and whether the firmware will like the hardware mismatches as the revision code will be wrong.

netlinker
Posts: 9
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Re: Spare BMC2837

Mon Sep 30, 2019 11:22 pm

Ok, I finally found the time to make a short Video and a picture showing the repair.
I will edit and upload the next days.
Both raspberries came back to life, but I confirmed the HDMI output to be dead.
Does anybody of the guys at Pi Towers know what it takes to ruin the output driver voltage/current wise?

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