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Buffalo Dac not powering up.. Drawing excessive current
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The ferrites are in series with each of the voltage regulator inputs. Follow the VD trace from the VDD header and you will run into the ferrite (each ferrite is marked L)
The best thing to do is figure out why your placid failed. Because even if the DAC were a complete short it should not have failed, this indicates there was something amiss. Knowing how it failed will probably lead us to our answer.
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Russ White wrote:The ferrites are in series with each of the voltage regulator inputs. Follow the VD trace from the VDD header and you will run into the ferrite (each ferrite is marked L)
The best thing to do is figure out why your placid failed. Because even if the DAC were a complete short it should not have failed, this indicates there was something amiss. Knowing how it failed will probably lead us to our answer. Ok.. I will pull the ferrite out... Yes.. I am already looking into why the placid failed... I will post something tomorrow (or even tonight).. maybe with photos... Right now - it looks like the one of the electrolytic caps... the board is being butchered as I type.. regs seem ok Meanwhile.. I am beginning to feel that my Buffalo is dead in the water. I am getting more convinced about that.. bummer... :-( Any chance I could mail it back to you 
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SORRY.... IT IS NOT A PLACID.. It is the LCDPS that was shipped with my opus... adding to the confusion!! I bought the kit back in Oct..  So sorry about that guys.. I feel dumb.. I can't keep up with all the acronyms Anyways.. investigating why the "LCDPS" failed..
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When you first connected the LCDPS to the BII, did you ensure beforehand that the output voltage of the LCDPS was reduced to 5V for the BII? I ask this because I have in the past rushed to power a project only to realise that I had not adjusted my power-supply to handle the load. On reading the documentation for the OPUS, it needs about 7.5V. I am not sure if pumping 7.5V into the BII will be enough to kill it.
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21hz Yes.. I adjusted it down.. see my post #9. After adjusting it down to 5V and connecting the buffalo.. it dropped to 4.7 and the buffalo did not turn on, the LED flickered momentarily. I disconnected everything in a jiffy (panicked really), ensured it was 5v open and reconnected.. then I went to do something else for about 10 mins - that is when it blew. I did not see it blow.. but I smelled it when I came back Russ/Brian.. I have confirmed the LM317 is certainly gone, L2 is open... and C6 is short... Looks like a massive failure of the entire left side!! I have replacing the cap and putting a spare 317 desoldered from something else (very hard to desolder!!). I have shorted L2 for now... Hopefully I will working in about an hour or 2... the board looks real bad  Buffalo still dead...
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hi i don't suppose your multimeter helps to give false or questionable readings if the multimeter battery is weakening every time you use it , was just an observation i noticed when i noticed your posted pictures with the multimeter . just a taught....  regard
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I was up late yesterday but managed to fix the LCDPS
Yes.. the LM317, one electrolytic cap and the inductor were gone. I was right on the money heh heh.. if I should say so myself..LCDPS is back up but looks like it went through a surgery. Tested it really really well and put is back for my Opus DAC... Although I am now running in stereo mode not dual mono. Will post pics in the evening since I have rush to work.
What went wrong - I have no idea. I am still of the opinion that the buffalo killed my LCDPS. I have used LM317s in the past and I know they have short circuit protection but when they are shorted - sometimes the breaker doesn't kick in and the overheat and die. Although this is pure speculation - I am following the bread crumbs
Oh well..
As a aside.. don't mean to hijack mu own thread - I put in an anode choke (10H) for the srpp (I bought it to use with the buffalo) stage after opus - and boy!! My opus sounds very very sweet now.. I can just imagine how buffalo would have sounded.
Regarding the multimeter.. yes ..batt is low.. good observation.. will replace it.. but I think the readings are still ok...
Russ/Brian - anymore ideas for the B2 before I give up... my wife has probably had it with me spending late nights in the basement :-)
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If this were me (just thinking out loud here), I would pull the AVCC headers and 2 position terminal block back off of there. Taking the Buff 2 back to "as received from TP". Short still there? Start isolating the VD runs as Russ suggested. Sorry if I've said something silly here, I don't have my Buffalo 2 yet.
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William
I did try that somewhere in the procees when I first realized the short... See my post from March 24th 4:09
"So in short.. even with the avcc not on board and the connectors no on board.. vdd and gnd were dead short"
I soldered the connections back the day before when I had to post pics for Brian showing the current draw etc. Until then it was not there.
But thanks for the suggestion.. I know everyone here is questioning my soldering skill after the first post :-) And understandabley so.. that picture was a bad one - in hindsight I shouldn't have posted it
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The fact the LEDs lit for a moment would indicate that at least initially there was no short. But there would be one created very quickly if there were any over voltage. Your LCDPS failure is very suspect. Without seeing what happened first hand all I can do is speculate what might have gone wrong with your LCDPS. But cap failure is usually an indication of either over voltage or reverse voltage.
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Russ White wrote:The fact the LEDs lit for a moment would indicate that at least initially there was no short. But there would be one created very quickly if there were any over voltage. Your LCDPS failure is very suspect. Without seeing what happened first hand all I can do is speculate what might have gone wrong with your LCDPS. But cap failure is usually an indication of either over voltage or reverse voltage. Russ The behavior of the B2 is still the same since the day I got it... the LED flickers for a moment (1/10th) of a second. It does that even now. Maybe I will post a video. And I am not sure I can convince you but now I am pretty sure the LCDPS failure was because of B2 (in terms of what came first). I am quite sure I can reproduce it by connecting the LCDPS to the board again and let it cook for 10 mins but I don't want to destroy it again. Or maybe in the interest of science I should sacrifice it :-) Lets see.. maybe I will do it tonight - take a video of the whole thing :-) Regarding the cap failure - I agree about that.. I know that from exp.. But I also know from exp that caps generally pop or bang in reverse volatage.. and in over voltage - they short or leak / deform. In this case - it was neither - it just resulted in a 20mv PP ripple on my scope. Seemed like it was a premature failure. I don't have an ESR measuring device but the symptoms look like it has a high ESR. The moment I replaced the ripple was gone. You will see it in the pics tonight when I get back home and post it Irrespective... I know my Buffalo is dead.. Quite sad about it.. was very much looking forward to doing an A/B compare with Opus. Thanks for all your help. I understand you are still suspect about the LCDPS causing the issue - sorry that I am not able to do anything to convince you otherwise.
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Considering you did not even know it was an LCDPS I am sure you can understand why I question the facts here. Not that I think you are trying to dishonest, I just don't think there is enough info to draw any conclusion. I would do as I suggested and measure the resistance from VD to GND in the original state, if it is a short, then remove ferrites one by one measuring after each. If you remove one and the short is gone, then you know that that supply or that part of the chip is dead. You won't have any chance at a repair unless you determine that.
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Yes I understand. My lack of understanding of the product TPA and the acronyms had put me at a disadvantage.. Apologies. Next time I will ensure that I use the right words as it pertains to the products
I have desoldered all the ferrites one by one and the short remains. Next I am going to check my original theory.. I will desolder them one by one too.
Thanks again for your help
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Rank: Administration
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The name on the PS is clearly marked, that is why I was surprised. If you have removed all of the ferrites correctly it is not physically possible that there is a short from VD to GND. As the VD trace is only on one layer and the ferrites are required to complete the circuits to the VREGs. There would have to be a short at the terminal block. Edited by user Friday, March 25, 2011 9:38:47 AM(UTC)
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I will certainly check what I am saying and get back to you in the evening.. Maybe I did not trace the VDD path clearly..
In any case you can help me when I post the photos
Again.. thanks for you help
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Please note I said to measure the resistance at VD, not VDD.
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"There would have to be a short at the terminal block..." this is what I keep thinking. The board has a direct short that melts power supplies, but everything stays pristine on the DAC, nothing gets hot, perfect traces, etc... (man, I wish I had this board in front of me)
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The only possible kind of short there would be a wire or a solder bridge. :) Also keep in mind, the way those VREGs fail is generally short to GND. The Ferrite test will tell the tale. Edited by user Friday, March 25, 2011 12:34:29 PM(UTC)
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What happens if you reverse polarity?
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Rank: Administration
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Not sure what your asking, reverse the polarity of the power supply? Or of the DMM leads? What?
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Buffalo Dac not powering up.. Drawing excessive current
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