I think Adrian is doing a good job in going slowly through the analysis. Sometimes you get the wrong way and that happens to all of us. Making interesting episodes is one thing, but having to repair something in time as the customer is waiting outside is another one.
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Like Usagi and others channels, as an old guy sitting in front of the screen, there are these moments where you scream at them, telling "There is the fault right in front of you!" but the guy on the screen is going the whole wrong way. But that is part of the fun.
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Back to the capacitors I have successfully replaced Tantalum types by Aluminum Polymer. These combine the benefit of being dry and having a low ESR. Even dry electrolyte sounds great and you want to replace all caps by this type, there are problems. You can replace Tantalum bei Al-Poly as the PSU is prepared for low ESR caps or there are small resistors in front of them (sometimes there are coils in front that filter but also add enough serial resistance)?
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Replacing Al-Electrolyte with Al-Poly will result in a big punch on the PSU on power-on but not as hard as if you replace low value AL-Electrolyte by MLCC ceramics. So the PSU needs to be prepared for that. And there is no way to replace Al-Electrolyte with AL-Poly in signal related places except you adapt surrounding inductance or resistance values.
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In any smaller test equipment like power-meters and such, especially when the supply is linear regulated, Al-Poly is good. But if you replace all more than 300 Al-Electrolytes by Al-Poly in a Stabilock 4031, you might trigger overload on power on of the PSU.?
But again, if you replace the 10uF caps on the 4031 CPU and secondary CPU board by 1uF Al-Poly or MLCC, that should work absolutely fine, as the series resistance is much lower and the energy required is transferred much faster. But the punch on the PSU is shorter and lower because of the reduced capacity. The Al-Poly will not go up in flames like to original ones and not peeing on the board like wet caps and eating the traces.
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And then again, replacing all SMD electrolytes in the small Stabilock 4015 by Al-Poly will cost over 170€ and may introduce different problems. Using Automotive or Aerospace certified Al-Electrolytes from the best brands you can get, will cost less then 80€ and make the unit work again for the next 40 years. And there is still hope, that modern Al-Electrolytes do not leak and eat your traces from the PCB, as the capacitors from the 2000'ds do when the capacitor plague was a thing.?
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73 de Ulrich
DC3AX / AG1U / OE3UPR
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DC3AX