@doubleDD "This "blind kid" has 10years of education in electrical engineering and was quite handy with all the instruments, including the oscilloscope, while he had the need to use them."
So good!.... you are familier with an O'scope.
And 10 years of education should provide you with some troubleshooting experience.
So good!.... you are familier with an O'scope.
And 10 years of education should provide you with some troubleshooting experience.
If a semiconductor start's to act up, it will not cure itself. It may stay useable with the existing fault for quite some time, but just as well can blow through in the next minute.
A regulator can fail completely open, so only the voltage it should deliver is missing, but as well produce a short. While one option may not harm any components, the other one can burn up the following parts with the then unregulated voltage.
I can not predict what will happen, so IMO the best option would be to fix what seems broken.
My comment about "learning". Even if you have worked in electronics a while ago, you probably will be surprised to see that much digital electronics in newer audio and scratch your head.
Also, if you have worked with an conventional osciloscope before, you may want to learn a few of the new (fantastic) functions of a digital scope.
If you think about buying a scope to fix the AVR, consider a new one, something anyone want's, like a Rigol DS1102Z-E.
Bought new for a good price (around €300), you will loose less than €50 if you sell it on eBay half a year later later. All the probes you need are included and new, always a gamble with used stuff.
It's been quite a while since the last "news"... I eventually received and managed to replace the LM317 (but only have a CPU thermal paste) and a bunch of nearby caps (quite sure with a lower quality ones). I also managed to lose one of the SMD resistors, and then replaced it with a regular one. And in the end...it did pretty much nothing. LM is still hot as hell, and some other chips on both digital and hdmi board get quite hot. One positive thing is that now it takes a bit longer to start crackling (cca 45-50min vs 20-30mins before), but that might be just cause AVR is now on working bench with a bit more airflow.
Since only thing that "needs" that LM are 2 DSP chips, it's quite possible that either something is wrong with them or with SMD caps and resistors around them. I'm still intrigued, but still haven't purchased an oscilloscope so there's nothing more I can do at the moment. (I might play further and go a different route and either extend the LM heatsink or install a ventilator to see if it changes anything)
I've said it before and I'll say it again, I couldn't have gotten this far without your help, so a big thanks to all contributors with constructive replies!
Since only thing that "needs" that LM are 2 DSP chips, it's quite possible that either something is wrong with them or with SMD caps and resistors around them. I'm still intrigued, but still haven't purchased an oscilloscope so there's nothing more I can do at the moment. (I might play further and go a different route and either extend the LM heatsink or install a ventilator to see if it changes anything)
I've said it before and I'll say it again, I couldn't have gotten this far without your help, so a big thanks to all contributors with constructive replies!
I would test the receiver with one speaker connected at a time, and so check all output channels one by one, to determine if all channels are affected or only one or two.
Maybe the problem is in the analog board.
At the input of each amplifier channel look for a pair of small transistors held together in close thermal contact with a piece of shrink tube.
A small shot of coldspray can diagnose the problem.
Maybe the problem is in the analog board.
At the input of each amplifier channel look for a pair of small transistors held together in close thermal contact with a piece of shrink tube.
A small shot of coldspray can diagnose the problem.
Did you try to use ice or cold spray? The are delivered with special tubes and jet's, so you can exactly hit one single part, with a little practice.
You can test each and any position, until you find the part that stops the crackling. Just need some care to get very little amounts out of the can at a time, not soaking the whole PCB.
You can test each and any position, until you find the part that stops the crackling. Just need some care to get very little amounts out of the can at a time, not soaking the whole PCB.
Thanks for chipping in! But if you go a bit back through my posts, you'll see that I tried every channel and it's preout, and that the only way to avoid the crackling sound is to use analog input with bypass mode, which led me (us) to believe that the problem is on the digital board. In this case -and this case only- AVR can run for hours without any crackling whatsoever.
I did try with the cold spray.
I did one more test, actually, I placed the speaker on the AVR unit and thus covered most of the ventilation holes on the top side. After about 30mins, AVR got real warm and the sound just cut off, no protection activated and otherwise looked completely functional (was using bluetooth input). Then I quickly removed the speaker and top cover, and cold sprayed only LM and it's heatsink (without turning anything off). Sound came immediately back and normal playback resumed for about 10mins, when it cut again. I didn't want to overstress it, so then I turned it off.
And even in the prior tests, spraying only the LM would stop the crackling for a couple of minutes.
So, as I said, in my thinking- only elements using the 1.8V produced by the LM are 2 DSP chips, so either they are somehow faulty, or some of the SMD components around those DSPs are faulty, or the replacement LM is of lower quality.
One thing that I didn't try though, and might try today- is spraying DSP chips when crackling starts.
Hi guys,
I find it quite impossible to find a conclusive resolve for the crackling issue.
First problem is that the crackling noises aren't constant, meaning once they start they are only present for a finite amount of time, afterwards the AVR works normally again. Then I have to switch it off and leave it for 15-30mins (to cool down?) before I can restart with the testing.
Second problem is that if I run the AVR open -meaning without device top cover and topmost board (HDMI)- then it's almost impossible to get the crackling noises at all. Probably there's enough air circulation that whichever part is overheating never gets too hot.
And third problem is that if I run the AVR closed (so that the heat can reflect from HDMI board and accumulate), it's difficult to check the temps and precisely shoot the cool spray on each component.
One thing that I did notice, is that one DSP is running a bit hotter then the other one - but it's also the one that is closer to LM, so again no conclusive answer could be made (chicken or egg; is it hotter because it's closer to very hot LM or is something wrong with it forcing LM to run that hot).
There's just too many variables to come to a definitive conclusion.
I find it quite impossible to find a conclusive resolve for the crackling issue.
First problem is that the crackling noises aren't constant, meaning once they start they are only present for a finite amount of time, afterwards the AVR works normally again. Then I have to switch it off and leave it for 15-30mins (to cool down?) before I can restart with the testing.
Second problem is that if I run the AVR open -meaning without device top cover and topmost board (HDMI)- then it's almost impossible to get the crackling noises at all. Probably there's enough air circulation that whichever part is overheating never gets too hot.
And third problem is that if I run the AVR closed (so that the heat can reflect from HDMI board and accumulate), it's difficult to check the temps and precisely shoot the cool spray on each component.
One thing that I did notice, is that one DSP is running a bit hotter then the other one - but it's also the one that is closer to LM, so again no conclusive answer could be made (chicken or egg; is it hotter because it's closer to very hot LM or is something wrong with it forcing LM to run that hot).
There's just too many variables to come to a definitive conclusion.