Okay, these definitely need replacing and it also brings me back (again) to the question: why are they bulged? Is it just age or is there another problem?
If these big ones have gone bad, how about the smaller ones?
all good questions
bulging can be caused by many reasons from heating to unstable electrolytes. depending on the dates could be related to the low esr formulations that got copied down wrong. remember the Dell computer caps debacle, They were produced in the year 1999 to 2003. Problems with capacitors produced with an incorrectly formulated electrolyte have affected equipment manufactured up to at least 2007.[2]?
bulging is a manifestation of pressure that built up inside...
but not enough to rapture the can top at the scorings...
but not enough to rapture the can top at the scorings...
japanese capacitors were not affected by capacitor plague, you can check brands in Parasound, assuming they only used authentic caps, no fakes.
I suspect low esr ( audio) caps from that era can have accelerated aging issues due to newer formulations, AFAIK the japs aren't perfect they tweak things as they learn. edit> If it says Japan on the plastic wrapper does that guarantee they aren't built at a Japanese contract house in Tawian ? IDK if things are that simple in the global market place.
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18 years old and maybe always powered? (auto on from standby), not really premature, could even be extraordinary long life ?
It could be the voltage rating. I am measuring ~60V across the caps which are rated 63V. By the way, they are still filtering very nicely.
We even had a thread on that (specifically on a NYTimes article on it). Other computers makers such as Apple were also affected, but they fixed their computers rather than denying there was a problem:
http://www.diyaudio.com/forums/everything-else/169516-tale-bad-capacitors-taking-company-down.html
Even if they're not bad (yet), you might as well replace them all (first measure the actual voltage across each, use voltage rating at least 20 percent higher) with long-life-at-high-temp caps so the new ones will last longer than the originals.
Yes indeed.
That sure sounds marginal. Caps are rated for maybe 10 to 15 percent surge voltage which would cover power line overvoltages, but that's meant to be temporary. Go for 75V or maybe even the next higher available rating.
We both were in that thread,
thanks for the time warp, again.
I think the OP has had his mind towards replacement.
wider voltage margins you speak of, are there for mains supply and XFMR regulation. operating with his measurements he can tighten those up esp. since he measured at light load at his location, by jumping up to the next range higher than 63V, will limit his replacement buying options considerably. One of my 80's high power amps sits exactly at 63V of 63VDC rated parts with no bulk cap issues dected.
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Is that 60 volts with a DMM? The peak might be a bit more, and that 60volts might be more on some days. Use higher voltage caps
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Im a pretty conservative engineer and I wouldnt hesitate to use tight margins based on a one off specific case. high volume production is another story. 60VDC at light loading with very small ripple voltage ! Heavy loading is where you need more ripple filtering and by then the rail droop helps
Take more measurements, perhaps at 2AM on a weekday.
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The overall point (at least the point I want to make!) is that all electrolytic capacitors have limited life (and there are many factors that affect life, including technology used in manufacture), and these are obviously at-or-near the end of their life. The good news is that you can spend a little more money on new ones that will last longer, perhaps even decades longer than these did.
And offhand, I didn't see anything in the ratings of devices marked "for audio" that made them any better or worse than others. IMHO the capacitor companies make those (surely a standard part with special marking) at the request of "high-end" audio equipment makers so they can use them and say "see, we use only The Best components, specifically made for high-end audio applications!"
And offhand, I didn't see anything in the ratings of devices marked "for audio" that made them any better or worse than others. IMHO the capacitor companies make those (surely a standard part with special marking) at the request of "high-end" audio equipment makers so they can use them and say "see, we use only The Best components, specifically made for high-end audio applications!"
the best thing for longer life is splurging on higher temp 105 caps and sticking to major name brands, I don't think running them at 20% lower voltage will compete in that dept given the same case size. look at life tests to arrive at MTBF targets
my point is> If you buy enough caps at price point, you can have them print anything (anything short of outright lies) on the label!
my point is> If you buy enough caps at price point, you can have them print anything (anything short of outright lies) on the label!
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If low ESR can cap not be used, I would deem it as circuit defect
The circuit should be able to handle even an ideal cap with the same capacitance, if a real resistance is needed for stability, a real resistor should be used in such design. Simply replacing a component with better spec causes problem, then I think the circuit needs revision.
The circuit should be able to handle even an ideal cap with the same capacitance, if a real resistance is needed for stability, a real resistor should be used in such design. Simply replacing a component with better spec causes problem, then I think the circuit needs revision.
I haven't found a higher temp spec cap that will fit. It looks like Nichicon (LS) has a 10000uF 80V that will physically fit. I had hoped to up the capacitance just for grins but it sounds like I am better off upping the voltage spec.
I do weigh this against the fact that Mr. Curl designed the amp with 63V caps. Granted, I believe he was constrained by the physical space. The previous model (HCA-1000) had 6800uF 63V, which I believe Mr. Curl pointed out was a compromise on uF due to lack of space. For the 1000A he was able to up it to 10000uF 63V. It seems Parasound would have had a real problem if they were truly undersized for voltage. But then I am measuring 60V (at 2:00am, low load).
I do weigh this against the fact that Mr. Curl designed the amp with 63V caps. Granted, I believe he was constrained by the physical space. The previous model (HCA-1000) had 6800uF 63V, which I believe Mr. Curl pointed out was a compromise on uF due to lack of space. For the 1000A he was able to up it to 10000uF 63V. It seems Parasound would have had a real problem if they were truly undersized for voltage. But then I am measuring 60V (at 2:00am, low load).
Like you, I have tremendous respect for Mr Curl, but reality is you can't actually be sure John spec'd that particular voltage cap in his design. The bean counters and manufacturing realities (space) can and do revise the work of the engineer. Perhaps it was more a case of ... "well, our tests say that 63V will work ..." rather than John saying "we need 63V caps here." Or maybe the higher voltage caps were not available in the standard catalog at the time with the parameters that were felt to be significant. Or maybe they used them because they knew from experience that particular cap from that particular manufacturer was known good at higher than rated voltage.
Parasound is, after all, a company that generally offers high value products; you don't get there without lots of effort at reducing manufacturing cost in the Bill of Materials (BoM) once the schematic is approved.
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