Not sure if I am posting this in the proper area so if it needs to go in another category, please let me know and I will change it or have a mod change it.
The problem: Long story short my Denon AVPA1HDCI pre/pro (high end - cost $7500 back in 2008) has had a problem with the sound levels which was traced to failing caps on the digital audio board. Denon will not repair it nor are any parts available from Denon (for several years now) and worse, Denon no longer makes the firmware/software available either so even if I found a NOS board, it would be useless because it would need bios/firmware loaded.
I took the board out and had a local PCB repair company (not a mom & pop electronics repair but a fairly large company of 100+ employees) replace all the electrolytic surface mount capacitors (about 50 of them). They only charged me a couple hundred bucks for labor as I supplied all the caps which I obtained from Digikey.
So, I get the board back in my pre/pro, test it with my headphones and all is OK. So I put it back in my rack, ran Audyssey to set speaker levels and so forth and all was good: I got sound through every speaker and Audyssey didn't detect any issues.
I then sat down to listen to some music and switched inputs on the pre/pro (changed HDMI inputs) and all of the sudden I get this very loud static noise from all speakers. I turn the volume down but to no effect. Fearing I might damage my speakers or something inside the pre/pro, I shut it down. Then the next day, I tried again and got the same results.
I took the board out and took it back to the PCB repair company and told them what I was hearing and they kept the board for 3 weeks and told me they found nothing wrong. I suspect there is some solder overflow or something that is shorting out but they said their solders looked good. They claim they checked it with a microscope and checked each cap for continuity but found nothing.
Does anyone have any idea what I should be looking for here? Could one of the caps be bad? There is a lot going on with the board: Lots of caps, chips and so forth. There are no hdmi ports on this board: Just composite and optical ports but it is the main audio board in the unit.
I do have a small local electronics repair guy that I can take it to and have him look it over but I would like to have some idea of what he should be looking for - he also is backed up and has told me he couldn't even look at it for 2 months.
Any insight is appreciated.
The problem: Long story short my Denon AVPA1HDCI pre/pro (high end - cost $7500 back in 2008) has had a problem with the sound levels which was traced to failing caps on the digital audio board. Denon will not repair it nor are any parts available from Denon (for several years now) and worse, Denon no longer makes the firmware/software available either so even if I found a NOS board, it would be useless because it would need bios/firmware loaded.
I took the board out and had a local PCB repair company (not a mom & pop electronics repair but a fairly large company of 100+ employees) replace all the electrolytic surface mount capacitors (about 50 of them). They only charged me a couple hundred bucks for labor as I supplied all the caps which I obtained from Digikey.
So, I get the board back in my pre/pro, test it with my headphones and all is OK. So I put it back in my rack, ran Audyssey to set speaker levels and so forth and all was good: I got sound through every speaker and Audyssey didn't detect any issues.
I then sat down to listen to some music and switched inputs on the pre/pro (changed HDMI inputs) and all of the sudden I get this very loud static noise from all speakers. I turn the volume down but to no effect. Fearing I might damage my speakers or something inside the pre/pro, I shut it down. Then the next day, I tried again and got the same results.
I took the board out and took it back to the PCB repair company and told them what I was hearing and they kept the board for 3 weeks and told me they found nothing wrong. I suspect there is some solder overflow or something that is shorting out but they said their solders looked good. They claim they checked it with a microscope and checked each cap for continuity but found nothing.
Does anyone have any idea what I should be looking for here? Could one of the caps be bad? There is a lot going on with the board: Lots of caps, chips and so forth. There are no hdmi ports on this board: Just composite and optical ports but it is the main audio board in the unit.
I do have a small local electronics repair guy that I can take it to and have him look it over but I would like to have some idea of what he should be looking for - he also is backed up and has told me he couldn't even look at it for 2 months.
Any insight is appreciated.
Looks like it's a particular capacitor (if it's a capacitor), as it is highly unlikely that all capacitors went bad in unison. I suggest you start by checking the largest, as the failure rate of electrolytic types is more or less inversely related to the energy / capacity.
Thanks. How do I check them or is it something I would need special equipment to do?
I have a basic DRO only but am willing to purchase what it would take as long as it isn't too expensive and/or technically complicated.
If your meter has capacitance measurement, then try that. It should read within 10%. Also check for visible damages like leaks or bulging. Also check the older set of capacitors for the similar damages.
Besides, what's that row of 12 components between the FPGA and the small chips that is not populated at all ?
Besides, what's that row of 12 components between the FPGA and the small chips that is not populated at all ?
Also check chip capacitors for damages like in the following picture (for example). If any of these smaller caps are damaged, many essential functions like the PLL etc. may not work properly. Also confirm what sampling frequency you switched inputs to, when this happened. Maybe the oscillator is damaged. Expensive boards sometimes have one each for the 48kHz and 44.1kHz families.
I'm afraid that the board may not be user serviceable, apart from replacing some regularly used components.
All the best.
I'm afraid that the board may not be user serviceable, apart from replacing some regularly used components.
All the best.
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The company that replaced the electrolytic caps discarded the old ones but they did not show any signs of leaking or bulging - what was happening was that the volume of the center channel (Primarily) was very slow to reach a listenable volume level (20 minutes or so) and eventually it never reached that level even after a long warm up. The known fix for this is to replace all the electrolytic caps on that board.
Except for the low volume level, It was working fine in all other respects before the recapping so my thinking is that one or more of the new caps that were installed is bad or something is shorted with the soldering that they did.
I would have thought the place that did the recap would have known how to check them but I wasn't looking over their shoulder so I don't know what they did or didn't do.
I will try to check the caps with my meter but I also read something about using those smart tweezers might work better for caps that are on the board???
Thanks.
Except for the low volume level, It was working fine in all other respects before the recapping so my thinking is that one or more of the new caps that were installed is bad or something is shorted with the soldering that they did.
I would have thought the place that did the recap would have known how to check them but I wasn't looking over their shoulder so I don't know what they did or didn't do.
I will try to check the caps with my meter but I also read something about using those smart tweezers might work better for caps that are on the board???
Thanks.
Since they didn't return the old components, are you sure they replaced all the capacitors? The smart tweezer, if you have access to one, is indeed a good tool for checking components.
To be clear, the only symptom right now is that one particular HDMI input produces static when selected?
I don't know that it was just one hdmi input - Since it was not something I could control with a volume adjustment, I shut it down right away in order not to damage anything so I wasn't really able to troubleshoot beyond the fact that when I ran Audyessy it was not doing it and when I listened via headphones it was not doing it - it only started when I switched to my Oppo player to stream some tunes.
I think I did switch off the Oppo hdmi back to another source but I don't recall - I was in a panic to avoid damage because it was so loud.
I am hesitant to put the board back in for more troubleshooting for this reason (potential damage).
I might try putting a volume attenuator after one of the output channels and disconnect the rest. Or just use a scope to look at the audio outputs. There is no reason to risk the whole hi-fi system when troubleshooting. You need to find out under what conditions the symptom occurs if you want to narrow down the possible list of causes.