Planet Audio PL3000.1D Capacitor questions

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It is easy to spot and replace bad components, especially blown capacitors. It is harder to answer the question "why" to the owner at times when it's just a capacitor failure.
This Planet Audio 3000.1D is another fine example of this situation. The capacitors are obviously bad, with not a single sign of overheating anywhere else in the amp and no bad input or output transistors. All the fixative is normal which typically you can tell when it gets cooked.
So while this is in waiting for capacitors to arrive I want to gain more of an understanding to answer the "why" question because it will be asked.

Is this ripple current, ESR change from internal heating, power supply sag or Undervoltage yet no other component failure or signs of stress. The thermal paste is not hardened.
Maybe bad capacitors? The paper that blew out is dry as there is no electrolyte? These are 63v 1000uf YUSCON TM low ESR series

Thank you for your input!
 

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It's common for the low-side to blow due to bad drivers but for both the positive and negative rail caps to blow is odd.

When you replace them (don't have to wait for the replacements, use anything near the original voltage and at least 1000uf per rail) and look for climbing voltage or possibly excessive (less likely). If there is excessive ripple, look at the duty cycle of the power supply.
 
It's common for the low-side to blow due to bad drivers but for both the positive and negative rail caps to blow is odd.

When you replace them (don't have to wait for the replacements, use anything near the original voltage and at least 1000uf per rail) and look for climbing voltage or possibly excessive (less likely). If there is excessive ripple, look at the duty cycle of the power supply.

Thank you Perry as I see where you are going with that information. Understanding current through a capacitor can be a task depending on the depth of physics and calculus one wants to get into. I rarely take ripple measurements as I may put too much trust into a design. I will be checking the voltages soon on this.

Too much power through poor quality capacitors, only 85℃ rated, could be anything.
More often than not, they suffer when too much current is required from them causing them to overheat and dry out, then explode as shown.

Thank you Jon also but these caps are 105c capacitors so I would assume capacitor derating was taken into account by the designers. Also when you say "too much current is required from them" does that not go back to power supply sag (in its basic definition) which leads to excessive heating of the power supply?
I typically see signs of overheating all around amplifiers when they have been pulled over the limit.
 
I may be using the term to loosely since it is not an industry calculation. Rated lifespan of a capacitor or failure at a maximum rated voltage at a given temperature. Each manufacturer has different CMF (common mode failure) specifications so I choose CD (Cornell) as I use them.
sin - CDE is the life-time and reliability applet for their snap-ins if anyone wants to see the relationship between temperature, voltage, and lifespan.

I don't think this amp failed from ambient temperature but rather a failure from the capacitor core temperature going back to ESR and ripple current. I am not trying to re-engineer this just trying to understand the failure point. I will know more when I get this off the diagnosis bench and onto the repair bench.
 
My suggestion is to replace the caps and drive the amp to full power while closely monitoring the voltage on the caps, the high frequency ripple and the temperature. Leave the graphs and tech spec to the engineers as far as this is concerned. The problem should be obvious. Caps are generally pretty tough to damage without obvious problems.

If you want me to leave this thread, let me know.
 
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