1 2 3 4 5 6 231 Replies Latest reply on Sep 25, 2012 5:22 AM by Roger Wolff Go to original post
      • 45. Re: RG1 1.8v regulator
        tmackay

        I'm certainly no engineer, so take what I have to say next with a grain of salt. It might be that you could get away with just cutting the 3 traces. The VDD18CORE pins of IC3 are linked internally and I have gotten away with running regulators without the decoupling/filter capacitors in the past. This would certainly be running out of spec, whether or not it is worse than forcing in current from an external higher potential source I don't know. I'll do some more testing when my IR Thermometer arrives.

        • 46. Re: RG1 1.8v regulator
          jamodio

          Even if you are able to place the decoupling caps not close as recommended to the pins, something is better than nothing.

           

          The internal regulator has no internal capacitance at all, running LDOs without or with the wrong caps may produce oscillation and not a reliable

          power source for the rest of the device.

           

          Here is an article that talks a little bit about the subject.

           

          PS. While datasheets are not always 100% accurate, complete or comprehensive, if a part says it needs a capacitor you should put the capacitor.

           

          -J

          • 47. Re: RG1 1.8v regulator

            maybe you could replace RG1 with a red LED.    A 1.4v

            forward voltage drop, leaving 1.9v, might be perfect to

            overpower the LAN chip, but still within 10% tolerance

            of 1.8v.

             

            Or maybe element14 will accept a RMA for a hot LAN chip

            and replace it with a board that runs cooler.

             

            p.s.

              I see this issue has made it to the other forum.

             

            http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=12387&start=23

             

            edited to add:

             

            jamodio, I see your 25 July 2012 post in the other forum in this thread:

            http://www.raspberrypi.org/phpBB3/viewtopic.php?t=6050&p=144439

            • 48. Re: RG1 1.8v regulator
              jamodio

              I reported the problem while ago on the "other forum" but since I'm a concern troll probably didn't count ....

               

              -J

              • 49. Re: RG1 1.8v regulator
                tmackay

                My IR thermometer arrived yesterday and I was able to take some more measurments. The laser sight is mounted off to the side, so it is necessary to scan around to find the hot spot. Measurements taken after 20min of video playback over network.

                 

                FN120508290 The first board the mod was applied to, still in a configuration where I can switch between the 1.8V power sources with a jumper.

                  Powered from RG1 exclusively

                    RG1 ____mV/IC3 ____mV idle (I forgot to measure this, will edit later as it might give an indication of each regulators ouput as a function of load)

                    RG1 ____mV/IC3 ____mV playback

                    45.7C

                 

                  Powered from IC3 exclusively

                    RG1 ____mV/IC3 ____mV idle

                    RG1 ____mV/IC3 ____mV playback

                    49.1C - hot spot seems to be larger

                 

                FN120744907 The second board which seemed to be running a bit warmer from the beginning

                  Unmodified (RG1 removed and replaced in previous test. Heat stress may have influenced result)

                    1837mV idle

                    49.9C playback

                 

                  RG1 removed

                    1837mV idle

                    50.7C playback

                 

                  Mod applied

                    RG1 1795mV/IC3 1845mV idle

                    RG1 ____mV/IC3 ____mV playback

                    46.0C - 49.5C (initially 46.0C after 20mins video playback, but it continued to rise for another 5 minutes or so)

                 

                I thought I was getting consistent results until that last measurement. Not sure what happenned, maybe it needs more time to equilibriate or there was an action scene. I measured again after leaving it overnight and still read 47.2C and climbing after at least 20 mins _at idle_ (lan plugged in, but no traffic, no video playback), then after another 10 minutes back down to 46.0C. Maybe this is normal, at least we seem to have elliminated the dependance on video playback.

                 

                The results seem to suggest that powering the 1.8V rail from IC3 might account for up to 4 degrees higher temperature on IC3. Looks like there might be quite a bit of variation in the LAN9512 chips based on the observed variation of VDD18CORE voltage so some may be affected more so than others.

                 

                This doesn't really confirm if this bug is the source of the _really_ hot LAN chips, but my chips don't seem to be in that category anyway (50C seems to be the norm from what I see). Perhaps some chips handle this extra current drain more gracefully than others though.

                 

                Here is the second attempt at the mod

                IMG_1026.JPG

                • 50. Re: RG1 1.8v regulator
                  tmackay

                  Tooms wrote:

                   

                  i will love to try out the hack Troy mackay has done also and then test again with that fix on the board, but i have looked into this and i most say it is very well done by Troy as i think it is to small for me todo and i done have an microscope as need for this.

                   

                  so yes if some one can findout where to make an cut to split the LAN9512 1v8 from the lod 1v8 then i will try this also.

                   

                   

                  Tooms

                  The microsope is really handy (and didn't cost me a cent), you'd be surprised what you can do when you can see what it is you are doing. I haven't even done a lot of SMD work. I'd love one of those IR cameras though... They'd be a bit harder to find in someones junk bin.

                  • 51. Re: RG1 1.8v regulator
                    jamodio

                    I really don't know how much effort to put on modifying the existing boards, what should happen is the RPF people acknowledge the problem, come up with a workaround, fix it for future boards and analyze the long term effects of THEIR ERROR.

                     

                    Don't think anybody will be open to a massive recall, but the right thing to do is TO FIX THE ERROR.

                     

                    My .02

                    -J

                    • 52. Re: RG1 1.8v regulator
                      tmackay

                      For $38 I don't expect a great deal of support, but I do expect that for a first revision board shipped naked without accessories or a case in limited numbers that it was never intended for the classroom in this form. More likely their target was developers and hackers to help mature the product, find bugs and develop software. I would hope that there will be future revisions, debugged, upgraded, shipped with a case and basic accessories, but I'm happy to tinker about with what I have; that is, after all, what I bought it for.

                      • 53. Re: RG1 1.8v regulator
                        jamodio

                        Well they missed the target for about couple of million miles. At the development phase price is irrelevant, and on the production phase what matters is cost, and not just components and assembly, you have to factor in that you will also need people and systems if you pretend to do a professional and serious job.

                         

                        Being a charity or non-profit doesn't mean you have to cry all the time about it, I'm associated with non-profits that deal with huge piles of money and have a full time staff to do the organization's job to deliver on their mission and goals.

                         

                        I think the argument "you get what you paid for" is very lame, I really don't care much about how much I paid for it or even if I had to pay much more to be part of what was promised to be an initiative to improve education on computer science.

                         

                        There are no clear indications that there will be future versions or revisions and trying to obtain any information on that front is almost impossible. The only thing they keep talking about is the model "A" which is the same thing less few components and the camera module.

                         

                        Still is a nice gadget to play with eLinux.

                         

                        -J

                        • 54. Re: RG1 1.8v regulator
                          morgaine

                          jamodio wrote:

                           

                          the right thing to do is TO FIX THE ERROR.

                           

                          My guess is that fixing the error(s) is ongoing right now, and that this is why Pete has returned to the job.

                           

                          There's total silence from RPF about it only because they can't yet figure out how to spin this into "Our perfect and faultless design is now even more perfect and faultless!".  But I'm sure that Liz will find a way.

                          • 55. Re: RG1 1.8v regulator
                            John Beetem

                            jamodio wrote:

                             

                            There are no clear indications that there will be future versions or revisions and trying to obtain any information on that front is almost impossible. The only thing they keep talking about is the model "A" which is the same thing less few components and the camera module.

                            Ironically, the Model A fixes the 1.8V regulator problem by not populating the LAN9512 , which also allows RasPi to run in a closed plastic case w/o heat problems.  Moderators at the RasPi Forum like to point out that the BCM2835 is used in cell phones without heat problems.  I don't recommend asking them how many cell phones have LAN9512 chips.

                            • 56. Re: RG1 1.8v regulator
                              jamodio

                              It was a good sign that Pete briefly showed up around here and somehow noticed and acknowledged that there are problems, but I'm not quite sure how much leverage he has.

                               

                              On the thread he showed up and mentioned "the list," I asked about "what else is on the list?" and the only thing I got so far is white noise.

                               

                              I already gave up trying to understand or figure what is going on with RPF, got tired of the default reaction and answer that "if there is something wrong with the Rpi the problem is YOU".

                               

                              -J

                              • 57. Re: RG1 1.8v regulator
                                morgaine

                                John Beetem wrote:

                                 

                                Moderators at the RasPi Forum like to point out that the BCM2835 is used in cell phones without heat problems.

                                 

                                The moderators live in a fanboi partition of reality where facts are an inconvenient irrelevance.  The BCM2835 is not known to have been used in anything other than Roku 2 until the Pi, and no BCM28xx series VideoCore has ever been used in a cellphone.

                                 

                                It's the same odd partition of reality in which the Pi is called a "low power consumption" computer, the same "low power" that caused plastic components in that balloon payload to melt, and the same "low power" that doesn't allow me to keep my finger on the LAN9512 for longer than reflex time.

                                 

                                Pity that XKCD isn't too interested in us.  There's enough material here for volumes.

                                 

                                Morgaine.

                                • 58. Re: RG1 1.8v regulator

                                  Troy,

                                  You wrote:

                                  "More likely their target was developers and hackers to help mature the product, find bugs and develop software."

                                   

                                  I think that is a widely held misconception.  Liz has explicitly said the

                                  product is not in beta test.  Eben has explicitly said it is for sale to

                                  anyone, not just developers and hackers.  If they were wanting to

                                  find bugs and mature the product, they would have a highly visible

                                  bug tracking system, and they would be eager to hear complaints. 

                                  Instead they ban people who complain, labelling them "concern trolls". 

                                  Jamodio ought to be a hero on the RPi forum for finding what is probably

                                  the most serious design error.  Instead, he is banned as a concern troll.

                                   

                                  JamesH has made clear that they have no intention of disclosing

                                  defects to potential buyers, and Abishur banned the guy yesterday

                                  who advocated disclosing the known USB problems, and who said

                                  he wouldn't have bought his RPi had he known.  Certainly they don't

                                  show even the slightest bit of sympathy for those who end up

                                  feeling duped.

                                   

                                  So my impression is that their target market is the unsuspecting

                                  buyer who is blinded by the low price.  I think they are afraid that

                                  their sales would dry up if they disclosed that the product isn't finished,

                                  and they seem to think that they can't afford to lose the sales to those

                                  who end up feeling duped.

                                  • 59. Re: RG1 1.8v regulator

                                    My IR thermometer arrived yesterday

                                    I was looking at picking one up, but noticed that even rather expensive ones seem to have a minimum measurement 'spot' of something around 20mm which is rather larger than the lan9512. I was wondering just how that affects the readings..  Presumably they average the total emissions over whatever is in the sensors view somehow.

                                     

                                    Like you I don't have a Pi that runs as hot as some reports, and without one it's difficult to form a theory on what the cause is.

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