Amazing that such a flaw could a) pass QC in the design phase and b) pass QC in the production phase. You'd think that someone would have noticed. Well done on finding that flaw - as you say it's rare that you have to pull IC sockets to find a fault! I had a similar loudness monitor in for repair last year but it was a 40A. That thing gave me the runaround. I can't even remember what I did to it, I think I changed out some suspect caps. It has a completely different power supply to the one you did here. A few months later it was back to its old tricks with random display issues. One day I will take another look at it.
What really surprises me is that these things have been presumably working since 1998 and the flaw shows up now. The other thing is that out of the 4 boards on this bank 3 were bad. Not a good track record. A little experimentation showed that any resistance to ground below 5M ohms will shut down that oscillator. I have 2 more banks of 4 to fix. We will see how that goes. Thanks for watching
@@AERVBlog No worries, I think I have mentioned before there aren't too many people on YT that repair broadcast equipment and that's my field as well so it's nice to see others doing it. For those boards to have run for so long without failure is surprising. Obviously when they were new, the resistance between the edge of the grounding copper and the pads was high enough not to be a problem. Perhaps grime and airborne impurities have settled on the board and caused a low enough resistance to be troublesome. The distance between the two copper lands is obviously very small. I'd be inclined to use a milling bit in the end of a Dremel tool and open up a larger gap.
@aervblog.. hats off to you sir... Amazing work and Discovery!!... Just did a video on this too... but I did not have the same problem... but did give thanks to you....
I just checked out your video. Thanks for the shout out. Nice find there. I have seen where the gas or mist that comes off the hot electrolyte tends to be conductive and invisible at the same time and since that chip uses such high impedance inputs that looks like that's all it took. Good job.
Thanks! I truly enjoy all your videos! This was very interesting. A more general question: Is it possible to troubleshoot most broadcast gear without a schematic? It seems that it would be near impossible to figure out the interconnection by simply looking at the PCB boards..
Is it possible? Yes, I guess so. It is like driving from New York to LA without a map of any kind and no road signs. Eventually you will get there but mostly by luck. There are people out there that make me look like a blind man navigating a maze, Mr. Carlson's Lab, Dave at EEVBlog, Shango66 just to name a few. They would have a better chance than I would. It is getting progressively harder as more and more functions are being taken over by MCUs and FPGAs. Without knowing the programming sometimes you just can't trace down a problem. Multi layer boards also make it much harder. Thanks for watching
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Amazing that such a flaw could a) pass QC in the design phase and b) pass QC in the production phase. You'd think that someone would have noticed. Well done on finding that flaw - as you say it's rare that you have to pull IC sockets to find a fault!
I had a similar loudness monitor in for repair last year but it was a 40A. That thing gave me the runaround. I can't even remember what I did to it, I think I changed out some suspect caps. It has a completely different power supply to the one you did here. A few months later it was back to its old tricks with random display issues. One day I will take another look at it.
What really surprises me is that these things have been presumably working since 1998 and the flaw shows up now. The other thing is that out of the 4 boards on this bank 3 were bad. Not a good track record. A little experimentation showed that any resistance to ground below 5M ohms will shut down that oscillator. I have 2 more banks of 4 to fix. We will see how that goes.
Thanks for watching
@@AERVBlog No worries, I think I have mentioned before there aren't too many people on YT that repair broadcast equipment and that's my field as well so it's nice to see others doing it.
For those boards to have run for so long without failure is surprising. Obviously when they were new, the resistance between the edge of the grounding copper and the pads was high enough not to be a problem. Perhaps grime and airborne impurities have settled on the board and caused a low enough resistance to be troublesome. The distance between the two copper lands is obviously very small. I'd be inclined to use a milling bit in the end of a Dremel tool and open up a larger gap.
@aervblog.. hats off to you sir... Amazing work and Discovery!!... Just did a video on this too... but I did not have the same problem... but did give thanks to you....
I just checked out your video. Thanks for the shout out.
Nice find there. I have seen where the gas or mist that comes off the hot electrolyte tends to be conductive and invisible at the same time and since that chip uses such high impedance inputs that looks like that's all it took. Good job.
Cool stuff man.
Thanks
Thanks! I truly enjoy all your videos! This was very interesting. A more general question: Is it possible to troubleshoot most broadcast gear without a schematic? It seems that it would be near impossible to figure out the interconnection by simply looking at the PCB boards..
Is it possible? Yes, I guess so. It is like driving from New York to LA without a map of any kind and no road signs. Eventually you will get there but mostly by luck. There are people out there that make me look like a blind man navigating a maze, Mr. Carlson's Lab, Dave at EEVBlog, Shango66 just to name a few. They would have a better chance than I would. It is getting progressively harder as more and more functions are being taken over by MCUs and FPGAs. Without knowing the programming sometimes you just can't trace down a problem. Multi layer boards also make it much harder.
Thanks for watching
@@AERVBlog Thanks! I suspected it could get quite complex without one.