I got a good deal on this off eBay. The seller indicated problems, but they seemed to involve only digital sound inputs. I mainly planned to use it for analog sound, so I figured that would be no problem.
It worked great for a few days until sound output to the speakers started disappearing when I switched input sources, including tuner.
While troubleshooting, I discovered if I flexed the top of the Audio/DSP card the sound would return, and the receiver would start working normally...for a while. The speaker relays can be heard switching when it is operating normally, but not when it isn't.
Then again a little later, no sound after switching sources. Again I flexed the card and the sound returned. So, brilliantly, I figured keeping the card flexed with a small cable tie would solve my problem! It did - for a few days. Then the problem returned.
I removed the card and inspected it carefully, and could not spot any obvious smoking gun. All solder joints, traces, connectors look normal. No bulging caps.
With these meager clues, is there a Denon AVR expert out there who could suggest what I should look for? Thanks.
The problem with bad solder joints and cracked traces is that they are often difficult-to-impossible to see.
We recently had a similar problem that was traced (joke intended) to a cracked trace under an IC.
I would start systematically unsoldering and resoldering every joint on the board. It's not enough to melt the solder and push it around. You need to suck or wick it off, then apply fresh solder, preferably eutectic (63/37).
How does your company make a living dealing with such dry joint problems by sucking or wicking every joint before resoldering ? Just interested, as I sure wouldn't be able to spare the time to approach it like that, and still keep it financially viable. For sure I agree that just reflowing the joints is not really enough, but I don't think that I know anyone else in the trade who deals with bad joints in any way other than just reflowing with a touch of new solder added, whether they are reworking an obvious bad joint, or carrying out a 'blanket solder-up' job of an area that has an invisible bad joint.
I do sometimes clean old solder right off, but only when there are obvious signs that the chemical composition of the joint has deteriorated beyond recovery - for instance where a joint has gone crystalline as a result of being subjected to continuous heat-stress from the component that it is connecting.
To the OP. I have had a number of problems with bad connectors on Denon AV amps. Just because the connectors 'look' good, I wouldn't immediately dismiss them as being blameless. It would be worth squirting some switch cleaner in, and then 'working' the connector in and out a few times. Also, if you have the facilities / expertise, its worth reworking the joints on the surface mount DSP ICs
It doesn't. I'm an individual who's been repairing electronic equipment, on and off, for almost 50 years.
I learned a long time ago that there are two ways to repair something -- find out exactly what's wrong, or do whatever's needed to get the damn thing working again. Neither is the "best" approach -- it depends on the problem.
In this case, it looks as if there's a bad solder joint -- or perhaps a cracked trace. It's less trouble to systematically resolder the joints than try to find the "bad" one. Note that two recent posters to this group have had good luck doing basically that.
The problem with just adding a bit of fresh solder is that there's no guarantee you're really getting the solder into its "liquidus" state. It's better to remove the solder altogether, so you can see what you're doing. If you have a SoldaPult, or a similar tool, it's not much trouble to quickly remove the solder from a dozen or so joints.
As far as the practicalities of removing old solder go, I have a proper vacuum rework station which removes solder from a joint almost as quickly as just resoldering it, but I still wouldn't, under 'normal' circumstances, use it to remove the solder from every joint on a board before resoldering. I think that it's probably down to a degree of how much time you have on your hands and personal preference, if you are an experienced solderer. I only questioned your original post because you said in it "we recently had a similar problem ..." I (obviously wrongly, sorry !) assumed that "we" referred to a repair shop. I don't have a problem with you using this total removal technique if that's what works for you.
I agree that sometimes a joint which appears to flow when an iron is applied, may not have reached a correct liquidus state throughout, but as an experienced solderer yourself, I'm sure that you would agree that when this happens, it is pretty obvious to the 'knowing eye', and that's the time I reach for the vacuum iron.
I would however, question the technique from a professional point of view, for finding *most* bad joints. There are very good techniques for finding the rogue ones - a can of freezer spray for instance - and a 'blanket' resolder of an area is always a last resort for me, if all other methods have failed. Particularly on a densely packed board, a 'blanket job' opens the way for creating further problems with unintentional ( and unspotted !) whiskers across joints. With the best will in the world, I think we would all agree, it happens ...
Interesting to hear how other people go about jobs, and how the juggling act of practicality versus profitability is looked at and resolved by individuals.
Of course, there's lead-free bad joints to contend with now, and as we all know, they defy *all* the proper techniques that we know and love ...
Again, to the OP. As you surmise, you will probably want to screw it back together before retesting - particularly any screws which pass through the back panel into phono ( RCA ) socket blocks which have a built in grounding strap at the screw hole. Some of these AV amps are super-critical of rear panel grounding, and can cause you no end of problems with the protect circuit cutting in with the slightest disturbance, as ground connections come and go ...
In my experience this is a matter of resoldering the flat-pack IC's on the DSP board. Your average doit-yourself-er is unlikely to have the necessary soldering skills or equipment to deal with the fine pitch of the IC leads involved.
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